﻿<?xml version="1.0" encoding="utf-8"?><Search><pages Count="184"><page Index="1" isMAC="true"><![CDATA[Post-traumatic stress disorder in adults
with mild intellectual disability:
Screening, assessment, and brief
intensive EMDR therapy
Anne Versluis]]></page><page Index="2" isMAC="true"><![CDATA[]]></page><page Index="3" isMAC="true"><![CDATA[Post-traumatic stress disorder in adults with mild
intellectual disability: Screening, assessment, and
brief intensive EMDR therapy
Anne Versluis]]></page><page Index="4" isMAC="true"><![CDATA[Colophon
This research was carried out within the Behavioural Science Institute (BSI),
Radboud Universiteit and ‘s Heeren Loo.
The research of this dissertation was funded by Scientific Research
Foundation ‘s Heeren Loo (grant number 15003) and ZonMw, Netherlands
Organization for Health Research (grant number 641001103).
Cover by Louise Poot, Paspartoe atelier, ‘s Heeren Loo, Noordwijk
Lay out by Ferdinand van Nispen, my-thesis.nl
Printed by Proefschriftenprinten.nl, Ede, The Netherlands
ISBN: 978-90-836732-9-5
Please cite as: Versluis, A.E. (2026). Post-traumatic stress disorder in adults
with mild intellectual disability: Screening, assessment, and brief intensive
EMDR therapy (Doctoral dissertation). Nijmegen: Behavioural Science
Institute, Radboud University, The Netherlands.
Copyright © 2026 by Anne Versluis. All rights reserved. No parts of this
dissertation may be reproduced, stored in a retrieval system or transmitted
in any form or by any means without permission of the author.]]></page><page Index="5" isMAC="true"><![CDATA[Post-traumatic stress disorder in adults with mild
intellectual disability: Screening, assessment, and
brief intensive EMDR therapy
Proefschrift ter verkrijging van de graad van doctor
aan de Radboud Universiteit Nijmegen
op gezag van de rector magnificus prof. dr. J.M. Sanders,
volgens besluit van het college voor promoties
in het openbaar te verdedigen op
donderdag 25 juni 2026
om 12.30 uur precies
door
Anne Eileen Versluis
geboren op 2 februari 1983
te Meerkerk]]></page><page Index="6" isMAC="true"><![CDATA[Promotoren:
Prof. dr. H.C.M. Didden
Prof. dr. A.D. de Jongh (Universiteit van Amsterdam)
Prof. dr. C. Schuengel (Vrije Universiteit Amsterdam)
Copromotor:
Dr. L. Mevissen (Mevissen Psychotrauma)
Manuscriptcommissie:
Prof. dr. mr. E. van Ee
Prof. dr. R.J.L. Lindauer (Universiteit van Amsterdam)
Dr. C. de Roos (Levvel)
Prof. dr. T.A.M.J. van Amelsvoort (Maastricht University)
Prof. dr. P.T. van der Heijden]]></page><page Index="7" isMAC="true"><![CDATA[Post-traumatic stress disorder in adults with mild
intellectual disability: Screening, assessment, and
brief intensive EMDR therapy
Dissertation to obtain the degree of doctor
from Radboud University Nijmegen
on the authority of the Rector Magnificus prof. dr. J.M. Sanders,
according to the decision of the Doctorate Board
to be defended in public on
Thursday, June 25, 2026
at 12.30 pm
by
Anne Eileen Versluis
born on February 2, 1983
in Meerkerk]]></page><page Index="8" isMAC="true"><![CDATA[PhD supervisors:
Prof. dr. H.C.M. Didden
Prof. dr. A.D. de Jongh (University of Amsterdam)
Prof. dr. C. Schuengel (Vrije Universiteit Amsterdam)
PhD co-supervisor:
Dr. L. Mevissen (Mevissen Psychotrauma)
Manuscript Committee:
Prof. dr. mr. E. van Ee
Prof. dr. R.J.L. Lindauer (University of Amsterdam)
Dr. C. de Roos (Levvel)
Prof. dr. T.A.M.J. van Amelsvoort (Maastricht University)
Prof. dr. P.T. van der Heijden]]></page><page Index="9" isMAC="true"><![CDATA[Table of contents
Chapter 1 General introduction 9
Chapter 2 Chapter 3 Chapter 4 Chapter 5 Reliability and validity of the Diagnostic Interview
Trauma and Stressors- Intellectual Disability
in adults with mild intellectual disabilities or
borderline intellectual functioning
Development and evaluation of the Trauma
Screener - Intellectual Disability (TS-ID): A PTSD
screening tool for adults with mild intellectual
disability or borderline intellectual functioning
Brief intensive EMDR therapy for PTSD in adults
with mild intellectual disability or borderline
intellectual functioning and behavioural problems:
A multiple baseline design study
Brief Intensive EMDR therapy with rotating
therapists: Experiences of adults with mild
intellectual disability or borderline intellectual
functioning, PTSD, and severe behavioural
problems
31
53
73
99
Chapter 6 General discussion 127
Appendices 147
Nederlandse samenvatting (Dutch summary) 149
Research data management and privacy statement 159
Dankwoord 163
List of publications 171
Curriculum Vitae 177]]></page><page Index="10" isMAC="true"><![CDATA[]]></page><page Index="11" isMAC="true"><![CDATA[Chapter 1
General introduction]]></page><page Index="12" isMAC="true"><![CDATA[]]></page><page Index="13" isMAC="true"><![CDATA[General introduction
Hilda is a 32-year-old woman with a mild intellectual disability.
Her parents were no longer able to provide the care she needed
when she was 12 years old. At that time, she started behaving
differently and showed much more aggression than before.
She was placed out of home and subsequently lived in various
care institutions for individuals with intellectual disabilities.
Hilda has been living in her current home for several months.
She receives intensive support from professional caregivers 24
hours a day. Since moving into her current home, the complexity
of her care needs has increased significantly. She frequently
exhibits physical and verbal aggression towards other residents
and professional caregivers. She often has trouble sleeping and
tends to isolate herself, particularly when she is with others.
According to her file, she has autism spectrum disorder in
addition to mild intellectual disability. During a meeting that was
held because the professional caregivers were concerned about
Hilda, one of them noted that her behaviour was very different
from what the team at her previous home had reported. While
her professional caregiver suspected that this might be related
to her autism spectrum disorder and her move to her current
home, he wondered if something else had happened. Given that
Hilda’s file also described a significant behavioural change at the
age of 12, the team decided to conduct a diagnostic interview for
trauma and stressor-related disorders. During the assessment,
Hilda revealed that she had been sexually abused several times
by someone when she was 12 and by a neighbour from her
current home several months ago. Following the diagnostic
assessment, Hilda was diagnosed with post-traumatic stress
disorder (PTSD). When the results were shared with her
parents and one of her professional caregivers, they were all
surprised to learn that she had experienced sexual abuse. This
was not documented anywhere in her file, and she had never
mentioned it. However, they also admitted that no one had ever
asked her about it. They agreed that PTSD symptoms should
be treated. Hilda decided to try eye movement desensitisation
and reprocessing (EMDR) therapy and was scheduled to see the
1
11]]></page><page Index="14" isMAC="true"><![CDATA[Chapter 1
therapist every Tuesday morning. However, she found EMDR
therapy too overwhelming. She suddenly bursts into tears when
she has to talk about her memories of sexual abuse during a
session, and it feels as if she is being re-abused. In the days
following therapy, she often thought about the sexual abuse and
became more aggressive. A few days after the session, Hilda
decided to discontinue therapy. “I’d rather forget about it than
have to think about everything again”, she told her caregivers.
Her PTSD symptoms have persisted, and problems in her daily
life, such as poor sleep, withdrawal, and behavioural problems,
continue.
There are many more individuals like Hilda, with a similar life history and
similar psychological and behavioural problems. Although emerging studies
suggest that post-traumatic stress disorder (PTSD) may be relatively
common in adults with mild intellectual disability or borderline intellectual
functioning (MID-BIF), it still often goes unrecognised in these individuals
(Mevissen et al., 2020a; Nieuwenhuis et al., 2019), partly due to the lack
of suitable diagnostic instruments until recently (Hoogstad et al., 2025).
Once diagnosed, it is important that individuals with MID-BIF receive PTSD
treatment, as untreated PTSD can cause serious problems (e.g. Benedict
et al., 2020; Davis et al., 2022; Gibson et al., 2020). Although the number of
studies is growing, especially on EMDR therapy in individuals with MID-BIF
(e.g. Byrne et al., 2020; Penninx et al., 2021; Verhagen et al., 2023), there
is still limited evidence regarding the effectiveness of EMDR therapy for
adults with MID-BIF, especially for those with severe behavioural problems.
Research in individuals without MID-BIF shows that intensive trauma-
focused treatment is particularly effective, as it leads to a relatively fast
reduction in PTSD symptoms and shows low dropout rates (e.g. Niles et al.,
2018). To date, no studies have explored the effectiveness of brief intensive
EMDR treatment in adults with MID-BIF and severe behavioural problems,
or how these individuals experience such an intensive format of trauma
treatment. Addressing these knowledge gaps is essential to improving
PTSD recognition and to developing more effective and tailored treatment
approaches for these individuals.
12]]></page><page Index="15" isMAC="true"><![CDATA[General introduction
The purpose of this dissertation is to improve the identification, diagnostic
assessment, and treatment of PTSD in adults with MID-BIF. This chapter
provides an introduction to the four studies of this dissertation. It starts
by a description and definition of (individuals with) MID-BIF and PTSD. It
then focuses on PTSD in individuals with MID-BIF, addressing the increased
risk, frequent under-recognition, and current challenges in diagnostic
assessment and screening. The chapter continues with an overview of
PTSD treatments for adults with MID-BIF, including EMDR therapy and
intensive trauma-focused treatment. Finally, it presents the aims and
outline of this dissertation.
1
Individuals with mild intellectual disability or borderline intellectual
functioning
According to the Diagnostic and Statistical Manual of Mental Disorders - Fifth
Edition, Text Revision (DSM-5-TR; American Psychiatric Association [APA],
2022) and the American Association on Intellectual and Developmental
Disabilities (AAIDD; Schalock et al., 2021), intellectual disability (ID) is
characterised by deficits in intellectual functioning, including reasoning,
problem-solving, planning, abstract thinking, judgement, academic
learning, and learning from experience, as confirmed by both clinical
assessment and standardised tests of intelligence. Additionally, deficits in
adaptive functioning must significantly impair an individual’s ability to meet
developmental and sociocultural standards for personal independence and
social responsibility. These deficits must be present in at least one of the
three domains of adaptive functioning: the conceptual domain (e.g., skills in
memory, language, reading, writing, mathematical reasoning, and practical
knowledge); the social domain (e.g., interpersonal communication, social
judgment, and the ability to form and maintain relationships); and the
practical domain (e.g., personal care, daily living skills, and independent
functioning). Deficits in adaptive and intellectual functioning must have
their onset during the developmental period of an individual.
Although the DSM-5-TR no longer defines ID based on strict IQ thresholds,
IQ ranges are still commonly used in clinical practice and research
contexts to describe ID levels associated with different degrees of severity.
Individuals with MID are generally considered to have IQ scores between
13]]></page><page Index="16" isMAC="true"><![CDATA[Chapter 1
approximately 50 and 70, and individuals with BIF with IQ scores between
70 and 85 (DSM-IV-TR, APA, 2000; Kaal et al., 2015). BIF does not meet
current diagnostic criteria for an ID in most countries. In the DSM-5-TR, BIF
is included under the V-code ‘Other conditions that may be a focus of clinical
attention’ and as one of the conditions that significantly affect treatment
or prognosis (APA, 2022). Individuals with BIF often experience functional
and contextual challenges similar to those with MID. Individuals with MID
and BIF are often grouped together since they share many characteristics
and support needs (Orío-Aparicio et al., 2025). Based on data from 2018,
the number of individuals with MID-BIF is estimated at 6.4% of the Dutch
population, amounting to approximately 1.1 million people (Woittiez et al.,
2019).
Mental health conditions, such as anxiety disorders, mood disorders, PTSD,
and behavioural problems are frequently reported and appear to have a
high prevalence among individuals with MID-BIF (Kildahl & Helverschou,
2024; Nieuwenhuis et al., 2019; Noel, 2018; Rittmannsberger et al., 2020;
Totsika et al., 2022; Westera et al., 2025). As a result of comorbidity, these
individuals often have intensive care needs (APA, 2022; Boat & Wu, 2015).
This dissertation focuses on individuals with MID-BIF, mental health
problems and behavioural problems, who receive intensive 24-hour care in
supported housings.
Post-traumatic stress disorder
According to the DSM-5-TR, PTSD is a mental health condition that arises
after exposure to a potentially traumatic event (Criterion A). An event
is considered potentially traumatic if it involves directly experiencing,
witnessing, or hearing about imminent death, serious injury, or sexual
violence against oneself or someone close. PTSD involves a range of
symptoms, including intrusive symptoms (PTSD cluster B), avoidance
symptoms (PTSD cluster C), negative alterations in cognition and mood
(PTSD cluster D), and alterations in arousal and reactivity (PTSD cluster
E). To be diagnosed, these symptoms must persist for at least one month
and cause significant distress or impair daily functioning, including social
or work-related activities (APA, 2022). Approximately 81% of individuals in
the Netherlands experience at least one potentially traumatic event during
14]]></page><page Index="17" isMAC="true"><![CDATA[General introduction
their lifetime. While most recover naturally from its psychological impact,
an estimated 11% develop PTSD at some point in their lives, with a current
prevalence of approximately 1.3% (Hoeboer et al., 2025). Whether an
individual develops PTSD following a potentially traumatic event depends
on various factors, including genetic predisposition, type and number of
traumatic events, and protective factors such as social context (Aftyka
et al., 2017; Brewin et al., 2000; Iversen et al., 2008; Lindsay et al., 2020).
Additionally, a low IQ is associated with increased vulnerability (Ozer et al.,
2003).
Undetected and untreated PTSD is associated with a wide range of adverse
outcomes, including sleep disturbances, substance abuse, delinquent
behaviour, elevated suicide risk, and increased healthcare costs due to its
long-term impact (Benedict et al., 2020; Davis et al., 2022; Gibson et al.,
2020; Marsiglio et al., 2014; Pietrzak et al., 2011). Despite these serious
consequences, there are often long delays between the onset of PTSD
symptoms and the initiation of appropriate treatment (Goldstein et al.,
2016; Pietrzak et al., 2012). To support timely recognition and improve care
pathways for individuals with PTSD, multidisciplinary treatment guidelines
for PTSD (Federatie Medisch Specialisten, 2025) in the Netherlands offers
evidence-based recommendations for the assessment and treatment
of PTSD in adults. The guidelines include references to individuals with
intellectual disabilities but make no mention of individuals with BIF, and
the recommendations for individuals with ID are predominantly based
on research conducted in the general population. While the guidelines
acknowledge the importance of considering intellectual disabilities when
diagnosing and treating PTSD, they do not specify how to select or adapt
appropriate diagnostic tools or treatment approaches for this group.
Furthermore, the guidelines assume that a suspected PTSD diagnosis is
present, despite PTSD often being particularly challenging to recognise in
individuals with MID-BIF (Mevissen et al., 2020; Nieuwenhuis et al., 2019;
see also the section: PTSD not recognised in individuals with MID-BIF).
Consequently, the characteristics and needs of people with MID-BIF may
not be fully addressed in these guidelines.
1
15]]></page><page Index="18" isMAC="true"><![CDATA[Chapter 1
PTSD in individuals with MID-BIF
Increased risk
Individuals with MID-BIF seem to be at increased risk of developing PTSD
compared to those in the general population (Mason-Roberts et al., 2018;
Mevissen et al., 2020a). This heightened vulnerability is likely related to their
more frequent exposure to potentially traumatic events compared to the
general population (McDonnel et al., 2019; Nieuwenhuis et al., 2019) and
might also be influenced by difficulties coping with and processing such
events due to limited cognitive and adaptive capacities. Studies conducted
in different care contexts have reported high PTSD rates among adults with
(suspected) MID-BIF. For example, Mevissen et al. (2020a) examined 106
adults with MID-BIF who were receiving care from an ID care service and
found a PTSD prevalence of 38%. Nieuwenhuis et al. (2019) conducted
study among 570 individuals with severe mental illness receiving 24-hour
care in a tertiary mental health care setting and reported a suspected PTSD
rate of 48% among those with suspected MID-BIF.
PTSD not recognised in individuals with MID-BIF
Although PTSD appears to be common among individuals with MID-BIF, it
often remains unnoticed in this group (Mevissen et al., 2020a; Nieuwenhuis
et al., 2019). Not recognising PTSD is also reflected in the findings of
Mevissen et al. (2020a) and Nieuwenhuis et al. (2019). For example, while
38% of participants in the study by Mevissen et al. (2020a) met the diagnostic
criteria for PTSD based on a standardised validated diagnostic interview
(i.e., the DITS-ID; see below), only 2% had a PTSD diagnosis recorded in their
electronic client files. Similarly, Nieuwenhuis et al. (2019) found that 48%
of individuals with suspected MID-BIF screened positive for PTSD, only 8%
had a PTSD diagnosis recorded in their files prior to assessment.
There are several explanations for not recognising PTSD in individuals with
MID-BIF. A first explanation is “diagnostic overshadowing”, a phenomenon
in which PTSD symptoms are misattributed to characteristics of ID or
symptoms of another mental health disorder that is already diagnosed
(Jopp & Keys, 2001; Wilsocki & Zalta, 2024). For example, intrusion
symptoms (PTSD cluster B) can be misinterpreted as hallucinations
belonging to a psychotic disorder, avoidance symptoms (PTSD cluster
16]]></page><page Index="19" isMAC="true"><![CDATA[General introduction
C) can be perceived as a consequence of limited adaptive skills, negative
alterations in cognition and mood (PTSD cluster D) can be incorrectly seen
as symptoms of an anxiety disorder or a mood disorder, and alterations
in arousal and reactivity (PTSD cluster E) may be mistaken for symptoms
of attention-deficit/hyperactivity disorder (ADHD) or to reflect a mismatch
between an individual’s social and emotional functioning and the social
context in which they live. As a result, PTSD symptoms may be inaccurately
attributed to symptoms of other mental health condition or an ID.
A second explanation for the under-recognition of PTSD in individuals
with MID-BIF is the overlap between behavioural problems and PTSD
symptoms, as described in Criterion E, which includes “Irritable behaviour
or angry outbursts (with little or no provocation), typically expressed as
verbal or physical aggression towards people or objects” and “Reckless
or self-destructive behaviour”. However, research suggests that this
relationship is more complex than symptom overlap alone. For example,
Rittmannsberger et al. (2020) found in a cross-sectional study that trauma
exposure was indirectly associated with behavioural problems through
PTSD symptoms. Because such behavioural problems are often highly
visible and disruptive in care settings, professionals may focus primarily on
managing these behaviours, thereby overlooking the possibility that these
are trauma-related (McNally et al., 2021). This mechanism differs from
diagnostic overshadowing in the sense that it does not involve attributing
PTSD symptoms to a specific diagnosis or ID but rather overlooking PTSD
as an underlying cause of the behavioural problems. These findings show
that trauma-related symptoms can be hidden by externalising behaviour,
making it harder to recognise PTSD in individuals with MID-BIF.
Finally, professional caregivers have limited knowledge of and awareness
of the trauma histories of individuals with MID-BIF. While a PTSD diagnosis
requires an understanding of traumatic events and their relationship with
current symptoms (APA, 2022), professional caregivers often lack insight
into their clients’ life histories. In many cases, traumatic events are not
documented in client files, and caregivers may not enquire about them
either. Professional caregivers are frequently unaware of the traumatic
1
17]]></page><page Index="20" isMAC="true"><![CDATA[Chapter 1
events that individuals with ID have been exposed to, which significantly
hinders the identification of PTSD in this group (Hoogstad et al., 2023).
These explanations illustrate the complexity of recognising PTSD in people
with MID-BIF, emphasising the need for suitable screening and diagnostic
tools to support accurate identification and assessment of PTSD.
Screening for PTSD in adults with MID-BIF
At the start of this research project, no screening instrument was available
that had been developed for adults with MID-BIF and aligned with the DSM-
5-TR criteria. The lack of a screener likely contributed to not recognising
PTSD in this group. Available PTSD screeners fall roughly into three
categories: those based on the DSM-5-TR but not validated for individuals
with MID-BIF, such as the PTSD Checklist for DSM-5 (PCL-5; Blevins et
al., 2015); those validated for individuals with MID-BIF but based on the
DSM-IV criteria, such as the Impact of Event Scale – Intellectual Disabilities
(IES-ID; Hall et al., 2014); and screeners that are both based on the DSM-IV
and not validated for people with MID-BIF, such as the Trauma Screening
Questionnaire (TSQ; Brewin et al., 2002), used in the study by Nieuwenhuis et
al. (2019). It is essential that a PTSD screener for individuals with MID-BIF is
both aligned with the current DSM-5-TR criteria and adapted and validated
for adults with MID-BIF. The DSM-5-TR introduced substantial revisions
in the conceptualisation and diagnostic criteria of PTSD, rendering earlier
instruments based on the DSM-IV no longer fully appropriate. Moreover,
individuals with MID-BIF have specific cognitive and communicative needs
that require feasible screening tools. Adaptations, such as simplified
language and visual support, are necessary to improve the comprehension
and reliability of self-reporting (Douma et al., 2025). The development and
validation of a DSM-5-TR based trauma screener tailored to the cognitive
and communicative capacities of adults with MID-BIF is therefore important
and is addressed in Chapter 3 of this dissertation. Without such a screener,
clinical practice risks delays in the recognition and diagnosis of PTSD,
ultimately impacting timely access to effective treatment.
18]]></page><page Index="21" isMAC="true"><![CDATA[General introduction
Diagnostic assessment of PTSD in adults with MID-BIF
There is growing attention in the literature regarding the assessment of
PTSD in individuals with MID-BIF (Hoogstad et al., 2025). Currently, the
Diagnostic Interview Trauma and Stressors – Intellectual Disability for adults
(DITS-ID-adults; Mevissen et al., 2018) is the only available instrument that
enables PTSD diagnosis based on the DSM-5-TR criteria (APA, 2022) in this
target group. This structured clinical interview showed good feasibility and
psychometric properties in a Dutch sample of adults with MID-BIF (Mevissen
et al., 2020a). The DITS-ID-adults demonstrated good inter-rater reliability.
Since there was no gold standard for assessing PTSD in individuals with
MID-BIF, Mevissen et al. (2020a) examined construct validity by analysing
the associations between PTSD diagnostic status, PTSD symptoms, and
symptoms of anxiety, depression, and subjective stress.
Although the DITS-ID-adults was found to be reliable and valid, this study
had a few limitations that should be noted. First, anxiety and depression
symptoms were measured using a proxy questionnaire, which may have led
to misinterpretation of symptoms owing to their subjective nature. Second,
behavioural problems were not assessed, whereas PTSD symptoms and
behavioural problems are known to be associated (Mason-Roberts et al.,
2018; McNally et al., 2021; Rittmannsberger et al., 2020). The DITS-ID-
adults is an important instrument for assessing PTSD in adults with MID-
BIF. Nevertheless, further research is necessary to strengthen the evidence
supporting its reliability and validity which is addressed in this dissertation
(Chapter 2).
PTSD treatment in adults with MID-BIF
Once PTSD is recognised and diagnosed in individuals with MID-BIF, it is
essential that they receive effective treatment. International guidelines for the
general population, such as those issued by the World Health Organization
(WHO, 2018) and the National Institute for Health and Care Excellence
(NICE, 2018), recommend Trauma-Focused Cognitive Behavioural
Therapy (TF-CBT) and Eye Movement Desensitisation and Reprocessing
(EMDR) therapy as first-line treatments for PTSD. This approach has been
endorsed and expanded in the Dutch multidisciplinary guidelines for PTSD
(Federatie Medisch Specialisten, 2025). The guidelines recommend that all
1
19]]></page><page Index="22" isMAC="true"><![CDATA[Chapter 1
adults with PTSD be offered trauma-focused psychotherapy, with a choice
from a broader range of evidence-based interventions, including imaginal
exposure, prolonged exposure, cognitive therapy, cognitive processing
therapy, imagery rescripting, Brief Eclectic Psychotherapy for PTSD (BEPP),
Narrative Exposure Therapy (NET), and EMDR therapy. The guidelines
explicitly emphasise that no individual should be excluded from treatment
based on personal characteristics, such as (mild) ID, and that interventions
should be adapted, where necessary, to ensure they are appropriate and
feasible for the individual. However, the guidelines do not specify how such
adaptations should be implemented.
EMDR therapy is currently the most extensively studied PTSD treatment
among individuals with MID-BIF and research suggests that it is a safe,
feasible, and potentially effective therapy for adults with MID-BIF (e.g.,
Byrne et al., 2020; Penninx et al., 2021; Verhagen et al., 2023). Given these
promising findings and its increasing use in clinical practice, this dissertation
focuses specifically on EMDR therapy.
EMDR therapy
EMDR therapy is an eight-phase, structured therapy aimed at resolving
symptoms resulting from traumatic memories (De Jongh et al., 2024;
Shapiro, 2018). The first phase consists of taking a case history and
developing a case conceptualisation. Phase two involves preparing the
participant for therapy. Phase three focuses on determining the target
memory. Phases four, five, and six involve memory processing to achieve
an adaptive resolution. An important part of the procedure involves
performing tasks that demand working memory. For example, the therapist
moves their fingers back and forth in front of the participant and asks them
to follow the movements while focusing on the traumatic memory. The
client is repeatedly asked to report on any emotional, cognitive, somatic,
and/or imagistic experiences that arise until internal disturbances reach
a subjective unit of disturbance (SUD) score of zero (0 = no disturbance
at all, ten = the highest possible level of disturbance), and the client rates
an adaptive and positive statement about themselves as fully believable
on a Validity of Cognition (VOC) score of seven (7 = completely true, 1 =
not true at all). Phase seven involves closing the session and preparing the
20]]></page><page Index="23" isMAC="true"><![CDATA[General introduction
participant for the period between sessions. Phase eight consists of re-
evaluation and integration.
The EMDR procedure is based on the adaptive information processing (AIP)
model, which suggests that it creates a physiological condition in which
unprocessed memories of traumatic events become linked to networks
that include adaptive information and skills (Shapiro, 2007). Retrieving a
traumatic memory is assumed to place a demand on the limited capacity
of the working memory. If another task is performed while retrieving a
traumatic memory, less capacity is available for recalling it. Consequently,
the memory is perceived as less intense and emotional; this theory is
known as the working memory theory (see De Jongh et al., 2024, for an
overview of the theoretical background of EMDR therapy). Research within
the general population shows that, in cases of persistently high subjective
unit of distress (SUD) scores, this may be reduced by performing additional
tasks that utilise working memory in addition to the original task. These
include activities such as tapping, counting, or solving a simple arithmetic
problem alongside the original task (Matthijssen et al., 2021).
There is an EMDR protocol for children and adolescents up to 18 years of
age (De Roos et al., 2025). This protocol includes the same eight phases
as the standard protocol developed by Shapiro (2018). It is adapted
for individuals with lower language skills, which seems to be suitable
and potentially effective for individuals with MID-BIF (Byrne et al., 2020;
Mevissen et al., 2011; Penninx et al., 2021; Schippers-Eindhoven et al.,
2024; Verhagen et al., 2023). Schipper-Eindhoven et al. (2024) conducted
a systematic review of 13 studies to identify and categorise the difficulties
therapists face when applying EMDR therapy to individuals with MID-BIF
and the adaptations used to overcome these difficulties. They divided the
adaptations made into three main categories: EMDR delivery (e.g., tuning
to the developmental level of the client, simplifying language, decreasing
pace), involvement of others (e.g., involving family or support staff during
or in between sessions), and the therapeutic relationship (e.g., taking more
time, adopting a supportive attitude).
1
21]]></page><page Index="24" isMAC="true"><![CDATA[Chapter 1
Intensive trauma-focused treatment
Evidence suggests that intensive trauma-focused treatment can be an
effective alternative to weekly trauma-focused treatment (Gahnfelt et al.,
2025; Hoppen et al., 2023; Hurley, 2018). The multidisciplinary guidelines
for PTSD (Federatie Medisch Specialisten, 2025) support this view and
explicitly recommend considering intensive trauma-focused treatment.
Intensive treatment can consist of various therapies, such as a combination
of prolonged exposure (PE) and EMDR therapy (e.g., Voorendonk et al.,
2023), or one type of therapy such as EMDR therapy alone (Hurley et
al., 2018). A common element in intensive trauma-focused treatment
is therapist rotation, meaning that different therapists deliver therapy
sessions throughout the treatment process. Intensive trauma-focused
treatments appear to offer a promising solution to the high dropout rates
often seen in traditional weekly trauma-focused treatments. Studies
indicate that between one-quarter and one-third of participants in weekly
trauma-focused therapy discontinue treatment, with some reporting even
higher dropout rates (e.g., Niles et al., 2018). These high dropout rates may
be due to a worsening of symptoms, which can be difficult to distinguish
from the temporary distress that is an inherent part of trauma-focused
therapy (Bongaerts et al., 2022; Van Woudenberg et al., 2018). In contrast,
intensive trauma- focused treatments have demonstrated considerably
lower dropout rates than other treatments. For example, Van Woudenberg
et al. (2018) reported a dropout rate of less than 3%, whereas Bongaerts et
al. (2022) reported no dropouts.
Intensive trauma focused-treatment with rotating therapists has shown
promising results in individuals with MID-BIF. A pilot study by Ooms-Evers
et al. (2021) investigated the effects of EMDR therapy and prolonged
exposure therapy in 33 children and adolescents with MID-BIF. The study
demonstrated a significant reduction in PTSD symptoms and in most
participants, the PTSD diagnostic criteria were no longer fulfilled after
treatment. Mevissen et al. (2020b) evaluated intensive trauma-focused
treatment consisting of intensive EMDR therapy for both children and their
parents, combined with parental skills training and two weeks of follow-
up parent support at home. The study involved six families, including nine
parents (six with MID-BIF) and ten children (all with MID-BIF). Significant
22]]></page><page Index="25" isMAC="true"><![CDATA[General introduction
decreases in PTSD symptoms and daily life impairment were observed in
children and parents. Additionally, parents showed a significant reduction
in general psychopathology and parenting stress after the intervention.
Despite these encouraging findings in children, adolescents, and their
families, the sample sizes and the number of studies on the effectiveness
of intensive EMDR therapy in adults with MID-BIF and severe behavioural
problems remain small, making it difficult to generalize the findings. This
dissertation aims to address this gap by investigating whether similar
positive outcomes can be achieved in this adult population (Chapter 4).
Clients’ experiences with intensive trauma-focused treatment
While initial evidence suggests that intensive trauma-focused treatment
may be effective for individuals with MID-BIF, little is known about how they
experience such treatment. A few studies have explored the experiences of
individuals in the general population, indicating that they perceive intensive
trauma-focused treatment as safe (Butler & Ramsey-Wade, 2024) and,
although demanding, worthwhile due to significant reductions in trauma
symptoms (Thoresen et al., 2022). Therapist rotation is also positively
evaluated in this population and is considered beneficial for treatment
effectiveness (Van Minnen et al., 2018).
Although research in this area is still limited for individuals with MID-
BIF. Further research is needed to understand how adults with MID-BIF
experience the intensity of trauma-focused treatment and the use of
rotating therapists, a topic addressed in Chapter 5 of this dissertation.
Aims and outline of this dissertation
The four main aims of this dissertation are as follows: first, to further
examine the psychometric properties of the adult version of the DITS-ID;
second, to develop and evaluate a PTSD screener for adults with MID-
BIF; third, to investigate the effectiveness of brief intensive EMDR therapy
for adults with MID-BIF and severe behavioural problems; and fourth, to
explore the experiences of individuals with MID-BIF and severe behavioural
problems who received this treatment. These aims serve a broader goal
of improving the identification, diagnostic assessment, and treatment of
PTSD in adults with MID-BIF.
1
23]]></page><page Index="26" isMAC="true"><![CDATA[Chapter 1
In line with the aims of this thesis, the structure and content are outlined
as follows: Chapter 2 reports a study assessing the reliability and
construct validity of the DITS-ID-adults The DITS-ID-adults, Brief Symptom
Inventory–18, Impact of Event Scale-Intellectual Disability, Anxiety,
Depression, and Mood Scale, and Behavior Problems Inventory were
administered to 97 participants with MID-BIF and their relatives. Chapter
3 focuses on the adaptation and evaluation of both the adult self-report
and proxy versions of the Trauma Screener-Intellectual Disability (TS-ID) for
adults with MID-BIF. The TS-ID was adapted from a child and adolescent
screener and administered to participants and proxies to examine internal
consistency, validity, and optimal cut-off scores for PTSD screening. Chapter
4 examines the safety and effectiveness of brief intensive EMDR therapy
conducted by a team of rotating therapists in adults with MID-BIF, PTSD,
and severe behavioural problems. Using a randomised non-concurrent
multiple baseline between-subjects design, PTSD symptoms, diagnostic
status, adverse events, behavioural problems, adaptive behaviour, and
involuntary care use were assessed. Chapter 5 explores the experiences of
individuals with MID-BIF, PTSD, and severe behavioural problems with brief
intensive EMDR therapy delivered by a team of rotating therapists. In-depth
semi-structured interviews were conducted with participants, professional
caregivers, and EMDR therapists before and after therapy to understand
their treatment experiences. Chapter 6 discusses the overall findings of the
studies that are part of this dissertation.
24]]></page><page Index="27" isMAC="true"><![CDATA[General introduction
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28]]></page><page Index="31" isMAC="true"><![CDATA[]]></page><page Index="32" isMAC="true"><![CDATA[]]></page><page Index="33" isMAC="true"><![CDATA[Chapter 2
Reliability and validity of the
Diagnostic Interview Trauma
and Stressors- Intellectual
Disability in adults with
mild intellectual disabilities
or borderline intellectual
functioning
This chapter was published as:
Versluis, A., Mevissen, L., de Jongh, A., Schuengel, C., & Didden, R.
(2025). Reliability and validity of the Diagnostic Interview Trauma and
Stressors–Intellectual Disability in adults with mild intellectual disabilities
or borderline intellectual functioning. Journal of Mental Health Research in
Intellectual Disabilities, 18(2), 204–220.]]></page><page Index="34" isMAC="true"><![CDATA[Chapter 2
Abstract
Objective: To assess the reliability and construct validity of the Diagnostic
Interview Trauma and Stressors- Intellectual Disability – Adult version
(DITS-ID-adults) in adults with mild intellectual disabilities or borderline
intellectual functioning (MID-BIF).
Method: The DITS-ID-adults, Brief Symptom Inventory–18 (BSI–18), and
Impact of Event Scale-Intellectual Disability (IES – ID) were administered to
97 participants with MID-BIF who lived in supported housing. The Anxiety,
Depression, and Mood Scale (ADESS) and Behavior Problems Inventory
(BPI) were administered to their relatives.
Results: The interrater reliability of the DITS-ID-adults was good to
excellent. The construct validity of the DITS-ID-adults was good, based
on positive correlations between the BSI–18, IES-ID, ADESS and DITS-ID-
adults, and mainly positive correlations between the BPI and DITS-ID-adults
(r = .21 to r = .75). Reporting potentially traumatic events listed under the A
criterium for PTSD was associated with fulfilling PTSD symptom criteria.
In this sample, 58% were classified with post-traumatic stress disorder
(PTSD) according to the DITS-ID-adults, while PTSD diagnosis on file was
low (7%).
Conclusion: The present findings support the DITS-ID-adults as a reliable
and valid basis for classifying PTSD in individuals with MID-BIF.
32]]></page><page Index="35" isMAC="true"><![CDATA[Reliability and validity of DITS-ID
Introduction
According to the DSM-5-TR, PTSD is characterized by symptoms of
intrusions, avoidance, negative alterations in cognition and mood, and
alterations in arousal and reactivity following exposure to a potentially
traumatic event. Such an event is defined under the A criterion when an
individual has directly experienced, witnessed or learned that a friend or
relative has been exposed to actual or threatened death, serious injury, or
sexual violence. PTSD symptoms last for at least one month and cause
distress in social or occupational functioning or functioning in other important
areas (American Psychiatric Association [APA], 2022). Individuals with mild
intellectual disability or borderline intellectual functioning (MID-BIF; IQ 50–
85) may be at a relatively higher risk of developing post-traumatic stress
disorder (PTSD) than people without an intellectual disability (ID; de Vogel
& Didden, 2022; Mason-Roberts et al., 2018; Mevissen & de Jongh, 2010;
Mevissen et al., 2016; Nieuwenhuis et al., 2019). While PTSD symptoms
are associated with a range of impairments and mental health conditions,
studies have found long delays from onset to treatment if diagnosis and
treatment are sought (Goldstein et al., 2016; Pietrzak et al., 2012).
PTSD frequently remains unnoticed in individuals with MID-BIF (Nieuwenhuis
et al., 2019), although PTSD symptoms manifest similarly in persons
with MID-BIF as in people without ID (Hoogstad et al., 2023; Mevissen et
al., 2016, 2020). In a cross-sectional study involving 570 severely mentally
ill participants to explore the presence of MID-BIF based on a screener
and PTSD, among the group with MID-BIF, there were much higher rates of
suspected PTSD (48%) than the number of PTSD diagnoses (8%) already
known in this sample before participating in the study (Nieuwenhuis et
al., 2019). A possible explanation for the difficulty in recognizing PTSD
in individuals with MID-BIF is that PTSD symptoms are attributed to the
characteristics of MID-BIF or another mental disorder, a phenomenon
called diagnostic overshadowing (Jopp & Keys, 2001). PTSD symptoms
show overlap with symptoms of anxiety and depressive disorders (Kildahl
& Helverschou, 2023; Kildahl et al., 2020a, 2020b), problems that occur at
least as often among people with an intellectual disability as in the general
population and for which recognition has been increasing (Emerson et
2
33]]></page><page Index="36" isMAC="true"><![CDATA[Chapter 2
al., 2023). As a result, PTSD symptoms may be wrongly attributed to these
disorders. The diagnosis of PTSD requires more than observing visible
behavior. A PTSD diagnosis requires knowledge of what traumatic events
a person may have experienced and could be linked to the emergence of
symptoms (American Psychiatric Association [APA], 2022). Undetected
and untreated PTSD in individuals in the general population has been
found to be associated with an elevated risk of other conditions, such as
substance abuse (Goldstein et al., 2016, revictimization (Graham-Kevan
et al., 2015), delinquency (Marsiglio et al., 2014), and decreased physical
health (Pietrzak et al., 2012). Therefore, a timely and adequate diagnosis of
PTSD is important in patients with MID-BIF (McNally et al., 2021).
A growing body of research has highlighted the need to assess individuals
with ID who have experienced psychological trauma. Although PTSD
symptoms manifest in people with MID-BIF in the same way as in
people without ID (Hoogstad et al., 2023; Mevissen et al., 2016, 2020), it
requires different diagnostic tools because questionnaires developed to
assess PTSD in people in the general population are often too difficult to
complete for people with MID-BIF due to the lack of simplified language
and supporting visualization (Kooijmans et al., 2022). A review by Daveney
et al. (2019) revealed that the adult version of the Diagnostic Interview
Trauma and Stressors – Intellectual Disability (DITS-ID-adults; Mevissen et
al., 2018) is the only instrument to establish a PTSD diagnosis in adults with
MID-BIF according to the DSM-5 criteria (American Psychiatric Association
[APA], 2013). The DITS-ID-adults is a clinical interview (taking approximately
45–60 minutes) and has been validated in a sample of 106 Dutch adults
with MID-BIF, living in supported housing or receiving ambulatory care
from an ID care service (Mevissen et al., 2020). The DITS-ID-adults proved
to be client-friendly, given that all participants in the study by Mevissen et
al. (2020) could complete the interview, and emotional dysregulation did
not occur. The interrater reliability of the DITS-ID-adults was good, and
its construct validity was supported by significant positive associations
between the scores on the Anxiety, Depression, and Mood Scale (ADESS)
and Impact of Event Scale – Intellectual Disabilities (IES-ID). However,
there are a few gaps in the study by Mevissen et al. (2020) that need to
be noted. First, anxiety and depression symptoms were measured using
34]]></page><page Index="37" isMAC="true"><![CDATA[Reliability and validity of DITS-ID
a proxy questionnaire, whereas feelings of anxiety and depression due to
their private nature may be missed by others. Second, behavioral problems
were not assessed, while PTSD symptoms and behavioral problems are
interrelated (Kildahl & Helverschou, 2023; Kildahl et al., 2020; Mason-
Roberts et al., 2018; McNally et al., 2021; Rittmannsberger et al., 2020).
The purpose of the present study was to assess the interrater reliability and
construct validity of the DITS-ID-adults in adults with MID-BIF. This study
replicated and extended the study by Mevissen et al. (2020) by examining
the construct validity of the DITS-ID-adults. We used the self-reported
Brief Symptom Inventory-18 (BSI-18) to measure symptoms of anxiety
and depression, and the Behavior Problems Inventory (BPI) to measure
behavioral problems. In addition, we used the IES-ID and ADESS, which
were also used in Mevissen et al. (2020) study. We hypothesized that there
would be positive associations between the number of symptoms on the
DITS-ID-adult and the presence or absence of a PTSD classification on one
hand, and questionnaire scores on the other (i.e., ADESS, BSI-18, BPI, and
IES-ID). In addition, we examined the association between reporting an
event that met Criterion A for PTSD and meeting the PTSD symptom criteria
(both measured with the DITS-ID-adults). We hypothesized that reporting a
Criterion A event would be associated with meeting PTSD symptom criteria
and that individuals meeting PTSD symptom criteria would report more
Criterion A events than those not meeting PTSD symptom criteria.
2
Materials and methods
Participants and Setting
Individuals with a mild intellectual disability or borderline intellectual
functioning (MID-BIF) who were all living in supported housing off two ID
care services in the Netherlands (i.e., ‘s Heeren Loo and Trajectum) were
informed about the aims of the study by their psychologist. Participation
was voluntary and individuals interested in participating received an
information letter. The inclusion criteria were that the participants were at
least 18 years old, had a diagnosis of MID or BIF, and had sufficient Dutch
language skills. Suicidality, drug use, and serious sedating medications
35]]></page><page Index="38" isMAC="true"><![CDATA[Chapter 2
(e.g., anxiolytics) were used as exclusion criteria. The study protocol and
detailed procedures were approved by the Central Committee Involving
Human Subjects of the Radboud University Medical Centre (reference
number: 2020–6967 – NL75909.091.20). After the study procedures had
been fully explained and after at least a week of consideration, 100 hundred
participants gave their written informed consent to participate in the study,
to record the interview on video, and to process the data anonymously. A
legal representative also signed up for clients who were not fully mentally
capable of providing consent to decide whether they wanted to participate
in the study or not.
Of the 100 participants who initially participated in this study, 97 completed
the interview with DITS-ID-adults. Only three participants (3%) terminated
the interview early; one participant did not understand the questions in
the event section, while two participants expressed that they felt sad at
the event section and, therefore, did not want to continue. Eventually, the
sample consisted of 97 adults (55 women and 42 men) with MID-BIF.
Their mean age was 32 years (range:18-73; SD = 14.07). IQ scores were
available for 92 participants; for 5 participants IQ score in their client file
were lacking, but their file specified that they had MID. The mean IQ was 68
(range:50-85; SD = 9.39); 52 participants had MID (54%), and 45 participants
had BIF (46%). Of the 97 participants, 37 (38%) had at least one additional
DSM-5 diagnosis in their medical record. Twenty participants (21%) were
diagnosed with autism spectrum disorder, four (4%) with mood disorder,
two (2%) with anxiety disorder, three (3%) with personality disorder, eleven
(11%) with attention deficit hyperactivity disorder (ADHD) and seven (7%)
participants had been diagnosed with PTSD prior to the study.
One-third (34%) indicated that they had received trauma treatment before.
To examine the association between reporting a PTSD criterion A event and
fulfilling the PTSD symptom criteria, only data from participants who had
not received trauma treatment (N = 64) were used. This is because trauma
treatment interferes with the association between reporting a Criterion A
event and PTSD symptoms, and one of the aims of trauma treatment is to
reduce PTSD symptoms. Data from all participants (N = 97) were used to
examine the construct validity and interrater reliability.
36]]></page><page Index="39" isMAC="true"><![CDATA[Reliability and validity of DITS-ID
Instruments
Diagnostic Interview Trauma and Stressors – Intellectual Disability – Adult
Version (DITS-ID-adults)
The DITS-ID-adults (Mevissen et al., 2018) is a Dutch clinical interview
(approximately 60 minutes) by which PTSD can be classified in adults with
MID-BIF based on the DSM-5 criteria for PTSD. The DITS-ID-adults protocol
systematically examines criteria A, B, C, D, E, F, G, and H to establish
whether an individual satisfies the complete set of criteria required for
the classification of PTSD. The DITS-ID-adults uses simplified language
and visual cues and consists of four sections. The first section consists
of 31 questions about potentially traumatic and stressful events. If the
participant answers “Yes” the interviewer asks the following question:
“What happened?,” after which s/he places the event on a timeline.
Based on the participant’s answer, it is determined whether or not it is an
A-criterion event. An example of a question is, “Have you ever been bullied?”
If someone answers that he/she has only been bullied with unpleasant
words, it is not scored as an A-criterion event; if someone says that the
bullying turned serious harm was inflicted, then the answer is scored as an
A-criterion. The symptom section includes 39 PTSD symptom questions,
of which 32 corresponding to the DSM-5-TR symptom list (PTSD criteria B,
C, D, and E). These are questions to which the participant can answer “Yes”
or “No.” The interviewer uses the answer category “Other” if the participant
answers with: “I don’t know” or “I’ve always had that” or gives an unclear
answer. In addition, four other potentially atypical symptoms (e.g., “Do you
have to do some things again and again or always in the same order?”)
are asked. Subsequently, a thermometer card (a visual cue) was used to
support the person to indicate the subjective level of daily life impairment.
This scale ranges from 0 (totally not) to 8 (very much), with a score of 4
or higher meeting the G criterion. Finally, if the interference score is four
or higher, the participant is asked when the symptoms started, from what
age, or after which event. This will help confirm whether symptoms have
been present for more than a month, which is necessary to classify PTSD
(criterion F). Finally, the interviewer assesses whether the symptoms are
not explained by medication, drug use, other medical conditions or somatic
disorders (criterion H).
2
37]]></page><page Index="40" isMAC="true"><![CDATA[Chapter 2
Brief Symptom Inventory −18, Revised Dutch Version (BSI–18)
The BSI–18 (de Beurs, 1993) is a multidimensional (Dutch) instrument that
measures self-reported psychological distress and psychopathological
symptoms in adults aged 18 and over; it measures the most common
psychopathological symptoms. The questionnaire consists of 18 questions
scored on a 5-point Likert scale of distress (0 = not at all, 1 = a little bit,
2 = moderately, 3 = quite a bit, 4 = extremely). It takes approximately five
minutes to complete the questionnaire. The BSI yields a total score (eighteen
items) and consists of the following three primary symptom dimensions:
“Somatization” (six items), “Anxiety” (six items) and “Depression” (six items).
The BSI–18 has demonstrated sufficient to good psychometric properties,
specifically internal consistency and discriminant validity, for (Dutch)
individuals with MID-BIF (Wieland et al., 2012). In our study, Cronbach’s alpha
for the BSI-18 total score was .95, for “Somatization” .88, for “Depression”
.88 and for “Anxiety” .89, indicating good to excellent internal consistency.
Behavior Problems Inventory (BPI)
The BPI-01 (Rojahn et al., 2001) is an instrument used for the assessment
of self-injury, stereotyped behavior, and aggression/destruction in
individuals with ID. In our study, we used the Dutch version of the BPI. This,
instrument which is completed by proxy indexes the frequency and severity
of problem behaviors and consists of three subscales: “Self-injurious
behavior” (eight items), “Aggressive/destructive behavior” (ten items),
and “Stereotyped behavior” (twelve items). The frequency of the problem
behavior is measured on a 5-point Likert scale (0 = never, 1 = monthly,
2 = weekly, 3 = daily, and 4 = hourly). The respondent’s subjective judgment
of the severity of the problem is measured on a 3-point Likert scale (1 = mild
problem, 2 = moderate problem, 3 = severe problem). A mean score for
both frequency and severity was calculated for each subscale and for
problem behavior overall. The Dutch version of the BPI has been found
to show adequate to good psychometric properties, including interrater,
intrarater, internal consistency and good convergent validity, compared
with the Aberrant Behavior Checklist (Dumont et al., 2014). In our study,
Cronbach’s alpha for the BPI total score was .86 (frequency) and .88
(severity), for “Self-injury behavior” .75 (frequency) and .77 (severity), for
“Aggressive/destructive behavior” .81 (frequency) and .89 (severity) and
38]]></page><page Index="41" isMAC="true"><![CDATA[Reliability and validity of DITS-ID
for “Stereotyped behavior” .88 (frequency) and .90 (severity), indicating
acceptable to excellent internal consistency.
Impact of Event Scale-Intellectual Disability, (IES – ID)
The IES – ID (Hall et al., 2014) is a self-report screening questionnaire
indexing subjective stress caused by potentially traumatic events. In our
study, we used the Dutch translation of the IES – ID. The IES – ID corresponds
to the three DSM-IV-TR PTSD symptom categories: avoidance, intrusion,
and hyperarousal. The instrument consists of 22 questions scored on a
3-point Likert scale (1 = a little bit, 2 = in the middle, 3 = a lot). No research
has been done on the psychometric characteristics of the Dutch version of
the IES-ID. The English version of the IES-ID has been found to have good to
excellent psychometric properties, including high internal consistency and
test-retest reliability, among individuals with MID-BIF (Hall et al., 2014). In
the present study, Cronbach’s alpha for the IES-ID total score was .94, which
indicates excellent internal consistency.
Anxiety, Depression, and Mood Scale (ADESS)
The ADESS (in Dutch: Angst Depressie en Stemmingsschaal; Anxiety,
Depression and Mood Scale [ADAMS]; Hermans et al., 2008) is a Dutch
questionnaire for measuring symptoms of anxiety and depression in
people with ID according to the DSM-5. This was accomplished by proxy
informants. The ADESS consists of four subscales: “Depressive mood”
(thirteen items), “Fear and tension” (seven items), “Social avoidance” (seven
items) and “Other problems” (eleven items). Each item of the ADESS is
scored on a 4-point Likert scale (0 = never/no problem, 1 = occasional/
minor problem, 2 = regular-moderate problem, 3 = frequent/severe
problem). The ADESS has sufficient to good psychometric properties
(i.e., internal consistency, test-retest reliability, and interrater reliability).
The ADESS showed sufficiently reliability as a screen for anxiety and
depression against the PAS-ADD Interview with (Dutch) adults with ID
(sensitivity between 73% and 88% and specificity range from 71% to 80%;
Hamers et al., 2018; Hermans et al., 2012). In the present study, Cronbach’s
alpha for the ADESS total score was .91, for “Depressive mood” .87, for
“Anxiety and stress” .74, for “Social avoidance” .84 and for “Other problems”
.73, indicating acceptable to excellent internal consistency.
2
39]]></page><page Index="42" isMAC="true"><![CDATA[Chapter 2
Procedure
The data were collected between November 2021 and June 2022. Trained
master students of Radboud University and Vrije Universiteit Amsterdam
and the first author conducted the DITS-ID-adults, then the BSI and finally
the IES-ID were administered to clients. Interviews were conducted in a
quiet room at the facility. All DITS-ID-adults’ interviews were recorded on
video to assess interrater reliability. Three participants did not complete
the DITS-ID-adults (see Participants and Setting). In addition, the BPI
and ADESS were sent by postal mail or e-mail to a person who knew the
participant well. Both, the BPI and ADESS were completed by the same
person for each participant: a professional caregiver for 83 participants
and by a parent or husband for 11 participants.
We randomly selected 35 recorded interviews to assess the interrater
reliability of the DITS-ID-adults. On a question-by-question basis, a second
independent rater scored all items of the event and symptom sections
of the DITS-ID-adults. The second rater assessed whether the event met
criterion A and whether the participant met the criteria for PTSD.
Statistical Analyses
SPSS version 27 was used to analyze the data. First, a descriptive analysis
was performed. To assess the interrater reliability of the DITS-ID-adults,
Cohen’s kappa was calculated for all items of the event section, symptom
section, whether the reported event met criterion A, and the presence or
absence of PTSD. To examine construct validity, correlation coefficients
were calculated between the BSI-18, BPI, IES-ID, ADESS and total number
of PTSD symptoms (DITS-ID-adults). Point-biserial correlations were
calculated between the BSI-18, BPI, IES-ID, ADESS and PTSD classification.
The association reporting a PTSD criterion A event and fulfilling the
PTSD symptom criteria was tested with chi-square and an independent
samples t-test to examine the difference between the mean number of
reported type A criterion events in participants who did and those who did
not fulfill the PTSD criteria. If more than 10% of the items of a total score
or subscale on the DITS-ID-adults, BSI-18, BPI, IES-ID or ADESS were not
scored, the scores of that scale were not included in the analyses (see
results for the number of participants per total scale and subscale). The
40]]></page><page Index="43" isMAC="true"><![CDATA[Reliability and validity of DITS-ID
correlation coefficients were interpreted using the criteria of Funder and
Ozer (2019).
Results
2
Descriptive Statistics
Of the 97 participants, 85 (88%) reported at least one A-criterion event in
their life and 56 of them (58%) were classified with PTSD using the DITS-
ID-adults. Table 1 lists the five event questions for which Criterion A was
identified most often. Cronbach’s alpha for the DITS-ID-adults total score
(sum of yes scores) on the symptom section was .86, which indicates good
internal consistency.
Table 1. Five most often cited potentially traumatic events.
Did someone ever touch your body even though you didn’t want this? Did someone ever hit you repeatedly or hurt you severely? Have you ever seen someone being threatened or maltreated (beating,
kicking, shooting, stabbing, going at someone’s throat)?
Did you ever experience a serious accident or a fire? Have you ever been forced to touch someone’s body parts when you
really didn’t want to
Number of times
mentioned
44 (45%)
33 (34%)
32 (33%)
21 (22%)
20 (21%)
Interrater Reliability
The interrater reliability for almost all items that tapped into whether
participants had been exposed to a particular event (29 items; yes, no, other)
was excellent (ҡ = .76–1.00). For one item of the event section (i.e., item 12:
“Did you ever see someone else being forced to have sex?”) the interrater
reliability was medium (ҡ = 0.48). The fact that kappa was lower for this
item was likely due to the skewed distribution because the percentage of
agreement on this item was high (94%). Kappa coefficients for fulfillment of
the A-criterion were excellent (ҡ = 0.77–1.00). The interrater reliability of 43
symptom-items was good to excellent (ҡ = 0.64–1.00). Finally, the interrater
reliability of the PTSD classification (yes/no) was excellent (ҡ = 1.00).
41]]></page><page Index="44" isMAC="true"><![CDATA[Chapter 2
Construct Validity
Association Between PTSD Symptom Scores and BSI–18 Scores
Correlations between DITS-ID-adults’ total number of PTSD symptoms
and PTSD classification (“yes” or “no”) and BSI–18 scores total score and
subscales (BSI–18 was completed by the participant), were strong to very
strong (see Table 2).
Table 2. Correlations between DITS-ID-adults total number of PTSD symptoms and PTSD
classification (‘yes’ or ‘no’) and BSI-18 scores (total score and subscales).
BSI–18
(‘yes’ or ‘no’)
PTSD classification
Number of PTSD symptoms
n r p n rpb p
Note. Pearson correlation coefficients (r) and point-biserial correlation coefficients (rpb) are used
for analyses.
Total score 97 .75 <.001 97 .61 <.001
Somatization 97 .64 <.001 97 .46 <.001
Anxiety 97 .70 <.001 97 .62 <.001
Depression 97 .73 <.001 97 .58 <.001
Association Between PTSD Symptom Scores and BPI Scores
No significant correlations were found between the DITS-ID-adults’
total number of PTSD symptoms and BPI frequency scores (BPI was
completed by proxy informants). However, moderate correlations were
found between the number of PTSD symptoms and the BPI total severity
score (n = 91, r = .28, p < .007), BPI self-injurious behavior severity score
(n = 94, r = .23, p < .024) and BPI stereotyped behavior severity score
(n = 93, r = .23, p < .028). No correlations between the PTSD classification
(“yes” or “no”) and the BPI total score or for the subscales of the BPI were
statistically significant (see Table 3).
Association Between PTSD Symptom Scores and IES-ID Scores
A very strong correlation was found between the total score on the IES-ID
completed by the participant and the total number of PTSD symptoms on
the DITS-ID-adults (n = 96, r = .81, p < .001) and the total score on the IES-
ID and the PTSD classification based in the DITS-ID-adults (“yes” or “no”)
(n = 96, r = .65, p < .001).
42]]></page><page Index="45" isMAC="true"><![CDATA[Reliability and validity of DITS-ID
Table 3. Correlations between DITS-ID-adults total number of PTSD symptoms and PTSD
classification (‘yes’ or ‘no’) and BPI scores (total score and subscales).
Number of PTSD
symptoms
(‘yes’ or ‘no’)
PTSD classification
BPI
n r p n rpb p
Total score Frequency 92 .21 .050 92 .12 .244
Severity 91 .28 .007 91 .18 .098
Self-injurious behavior Frequency 93 .19 .066 93 .11 .277
Severity 94 .23 .024 94 .14 .178
Aggressive/destructive behavior Frequency 92 .09 .415 92 .06 .601
Severity 92 .14 .194 92 .07 .540
Stereotyped behavior Frequency 95 .17 .106 95 .10 .326
Severity 93 .23 .028 93 .16 .122
2
Note. Pearson correlation coefficients (r) and point-biserial correlation coefficients (rpb) are used
for analyses.
Association Between PTSD Symptom Scores and ADESS Scores
Moderate to strong correlations were found between the DITS-ID-adults
(completed by the participant), total number of PTSD symptoms, and
PTSD classification (“yes” or “no”) and ADESS scores (completed by proxy
informants) in terms of overall score and subscales (see Table 4).
Association Between Reporting a PTSD Criterion A Event and PTSD
Symptom Criteria
Results of a chi-square test (in the group of participants who had not received
trauma treatment) showed that participants who reported a criterion A event
significantly more often fulfilled all PTSD symptom criteria (criteria B, C, D,
E, F, G, and H) compared to participants who did not reported a criterion A
event (x2 (1) = 5.52, p = .022). The results of an independent samples t-test
showed that participants who met all PTSD symptom criteria reported more
potentially traumatic events (M = 4.26; SD = 3.19) than those who did not
meet all PTSD symptom criteria (M = 1.76; SD = 1.68), t(62) = 3.80, p < .001.
43]]></page><page Index="46" isMAC="true"><![CDATA[Chapter 2
Table 4. Correlations between DITS-ID-adults total number of PTSD symptoms and PTSD
classification (‘yes’ or ‘no’) and ADESS scores (total score and subscales).
(‘yes’ or ‘no’)
PTSD classification
ADESS
Number of PTSD symptoms
n r p n rpb p
Note. Pearson correlation coefficients (r) and point-biserial correlation coefficients (rpb) are used
for analyses.
Total score 95 .46 <.001 95 .40 <.001
Depressive mood 95 .45 <.001 95 .37 <.001
Anxiety and stress 95 .48 <.001 95 .42 <.001
Social avoidance 95 .28 .006 95 .26 .012
Other problems 96 .38 <.001 96 .40 <.001
Discussion
The interrater reliability of the DITS-ID-adults was good to excellent. Results
support the construct validity of the DITS-ID in light of the relationships
found with the other measures used in this study. We found a significant
association between having been exposed to an event that meets the A
criterium for PTSD and fulfilling PTSD symptom criteria.
To this end, our results replicate and extend the findings of Mevissen et al.
(2020) who also found positive correlations between the total number of
PTSD symptoms and PTSD classification (based on the DITS-ID-adults) and
IES-ID and ADESS. Filling a gap left by the study by Mevissen et al. (2020), the
correlation between BSI-18, BPI, and DITS-ID-adults was examined. Positive
correlations were found between the total number of PTSD symptoms
and the PTSD classification and the BSI-18, which measures self-reported
somatization, anxiety, and depression. This was expected because of the
positive association between PTSD symptoms and anxiety and depression
symptoms (Mason-Roberts et al., 2018; Spinhoven et al., 2014). Moderate
positive correlations were found between the total number of PTSD
symptoms and most of the (severity) BPI subscales, which may also be
expected because of the association between PTSD symptoms and
behavioral problems (Goldstein et al., 2016; Kildahl et al., 2020; Mason-
Roberts et al., 2018; McNally et al., 2021; Rittmannsberger et al., 2020).
No correlations were found between the BPI subscale, “Aggressive/
44]]></page><page Index="47" isMAC="true"><![CDATA[Reliability and validity of DITS-ID
destructive behavior” and the total number of PTSD symptoms and the
PTSD classification. There may also be explanations other than PTSD for
the presence of aggression problems. An illustrative example of another
influencing factor is frustration with basic psychological needs (autonomy,
relatedness, competence). Research indicates that individuals with MID-
BIF more frequently experience frustration with these basic psychological
needs, and this frustration is linked to the expression of externalizing
behavioral problems (Westera et al., 2023). Overall, it can be concluded that
the DITS-ID-adults is a useful instrument to classifyPTSD in people with
MID-BIF, assessing a sample of participants who were exclusively living in
residential care. Overall, it can be concluded that the DITS-ID-adults is a
reliable and valid instrument to assess PTSD in people with MID-BIF.
Reporting a potentially traumatic event (A-criterion) was associated with
fulfilling the PTSD-symptom criteria. Furthermore, people who met the PTSD
symptom criteria reported more potentially traumatic events (criterion A)
compared to those who did not meet the PTSD symptom criteria. This is in
line with the study by Mevissen et al. (2020) and underpins the cumulative
effect of trauma (Kessler et al., 2017); experiencing a potentially traumatic
event increases the likelihood of reporting more potentially traumatic
events.
2
PTSD is unrecognized
Of the 97 participants, 88% had reported at least one A-criterion event
in their life, and 58% of the participants could be classified with PTSD
according to the DITS-ID-adults. This is remarkably high, as only 7% of
the participants were diagnosed with PTSD before participating in the
study. Mevissen et al. (2020) and Nieuwenhuis et al. (2019) also found
higher rates of PTSD diagnosis in their sample of participants than
the rates known in advance. These data support the notion that PTSD
is unrecognized in people with MID-BIF. Possibly because of the lack of
evidence for appropriate diagnostic tools and missing guidelines in the
field of PTSD in people with MID-BIF, diagnostic testing is rarely performed.
Another possible explanation for not recognizing PTSD in individuals with
MID-BIF is that PTSD symptoms are attributed to MID-BIF, a phenomenon
known as diagnostic overshadowing (Jopp & Keys, 2001). In addition, PTSD
45]]></page><page Index="48" isMAC="true"><![CDATA[Chapter 2
symptoms may be incorrectly attributed to other mental disorders (Kildahl
& Helverschou, 2023). For example, intrusion symptoms (PTSD criterion B)
can incorrectly be interpreted as hallucinations belonging to a psychotic
disorder, and alterations in arousal and reactivity (PTSD criterion E) may
appear to be manifestations of ADHD. Finally, the difficulty to recognize
PTSD in this target group could be explained by the fact that caregivers are
often insufficiently aware of the trauma history (Hoogstad et al., 2023) and
PTSD symptoms (Versluis et al., 2025) of the individuals they work with.
As stated in the Introduction, undetected and untreated PTSD is related
to serious problems in daily life, which may specifically hold true for
individuals with MID-BIF (McNally et al., 2021). It is important that PTSD
is better recognized in people with MID-BIF so that they can receive proper
treatment. In recent years, an increasing number of studies have shown
that trauma treatments, such as EMDR therapy, are suitable, safe, and
potentially effective for adults with MID-BIF who have been diagnosed with
PTSD (e.g., Penninx Quevedo et al., 2021; Unwin et al., 2018).
Limitations of the Study
The present study has limitations. First, since the introduction of DSM,
MID and BIF should no longer be diagnosed by an IQ-score alone. When
determining a MID or BIF, adaptive functioning should be considered
in addition to the IQ score. All participants in this study were previously
classified with MID or BIF as mentioned in their client file, but often the
classification was based only on an IQ score and not on their adaptive
skills. The latter is due to the lack of an up-to-date Dutch language and
standardized instruments for measuring adaptive skills in people with MID-
BIF. Consequently, it remains uncertain whether all participants would fulfill
all DSM-5-TR criteria for MID or BIF. Second, we investigated a specific
sample of adults with MID-BIF all living in supported housing in two ID care
services, which implies these findings may not be generalizable to the MID-
BIF population in general.
Recommendation for future Research
The DITS-ID-adults contains a follow-up measurement, with which a
clinician can assess whether there is still a PTSD classification and/or
46]]></page><page Index="49" isMAC="true"><![CDATA[Reliability and validity of DITS-ID
whether the number of PTSD symptoms has decreased following trauma
treatment. However, given that, until now, no data are available on the
test-retest reliability of the DITS-ID-adults follow-up measurement, future
studies should address this issue. Availability of these data is important
as this would enable clinicians to assess whether the difference in scores
on the follow-up measurement before and after an intervention reflects a
reliable change.
Conclusion
This study underscores the importance of recognizing and classifying PTSD
in individuals with MID-BIF, as it is often overlooked. Our findings support
the DITS-ID-adults as a reliable and valid basis for classifying PTSD for this
population. It is imperative for healthcare and psychology professionals to
become aware of the potentially high risk of PTSD in individuals with MID-
BIF and consider the use of DITS-ID-adults as a valuable tool for classifying
PTSD in individuals with MID-BIF.
2
Acknowledgments
The authors thank the students for their contribution to the data collection
and all the participants, involved family members and caregivers who
participated in the study.
47]]></page><page Index="50" isMAC="true"><![CDATA[Chapter 2
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2
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Versluis, A., Schuengel, C., Mevissen, L., de Jongh, A., & Didden, R. (2025). Development and
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2240732
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50]]></page><page Index="53" isMAC="true"><![CDATA[]]></page><page Index="54" isMAC="true"><![CDATA[]]></page><page Index="55" isMAC="true"><![CDATA[Chapter 3
Development and evaluation
of the Trauma Screener -
Intellectual Disability (TS-
ID): A PTSD screening tool for
adults with mild intellectual
disability or borderline
intellectual functioning
This chapter was published as:
Versluis, A., Schuengel, C., Mevissen, L., de Jongh, A., & Didden, R.
(2025). Development and evaluation of the Trauma Screener-Intellectual
Disability: a post-traumatic stress disorder screening tool for adults with
mild intellectual disability or borderline intellectual functioning. Journal of
Intellectual Disability Research, 69(2), 127–136.]]></page><page Index="56" isMAC="true"><![CDATA[Chapter 3
Abstract
Background: This study aimed to evaluate the validity and reliability of the
adult self-report and proxy version of the Trauma Screener-Intellectual
Disability (TS-ID) in adults with mild intellectual disability or borderline
intellectual functioning (MID-BIF). An optimal cut-off value was determined
for the ratio of specificity to sensitivity for predicting the diagnosis of post-
traumatic stress disorder (PTSD).
Methods: The TS-ID was adapted from a Dutch Child and Adolescent
Trauma Screener, for use with adults with MID-BIF. Outcomes based on
the TS-ID were compared with the presence of PTSD, as classified using
the Diagnostic Interview Trauma and Stressors–Intellectual Disability
(Mevissen et al., 2018). The TS-ID adult version was administered to 97
participants with MID-BIF who lived in supported housing, whereas the TS-
ID proxy version was administered to 92 family members or professional
caregivers.
Results: The TS-ID adult version showed high internal consistency
(Cronbach’s α = .94) and excellent validity (AUC = .94) for distinguishing
PTSD in adults with MID-BIF. Optimal specificity and sensitivity was found
at a cut-off score of 18. Although the TS-ID proxy version demonstrated
excellent internal consistency (Cronbach’s α = .93), it showed no validity in
statistically distinguishing PTSD in adults with MID-BIF.
Conclusions: The TS-ID showed favourable psychometric qualities as a
screening instrument of PTSD in the case for people with MID-BIF.
54]]></page><page Index="57" isMAC="true"><![CDATA[Development and evaluation of TS-ID
Introduction
Post-traumatic stress disorder prevalence in individuals with mild
intellectual disability or borderline intellectual functioning
People with mild intellectual disability or borderline intellectual functioning
(MID-BIF) (IQ 50–85) experience many negative life events (McDonnell et
al., 2019) and may develop post-traumatic stress disorder (PTSD) more
often than the general population (de Vogel & Didden, 2022; Mason-
Roberts et al., 2018; Mevissen et al., 2016; Nieuwenhuis et al., 2019). The
DSM-5-TR criteria for PTSD include exposure to actual or imminent death,
serious injury and/or sexual violence, followed by symptoms of intrusions,
avoidance, negative alterations in cognitions and mood and alterations
in arousal and reactivity. PTSD symptoms last for at least 1 month and
cause distress in social or occupational functioning or functioning in other
important areas (American Psychiatric Association, 2022). PTSD has
been found to be associated with several other mental health problems
(Goldstein et al., 2016; Pietrzak et al., 2012), which may be especially the
case in individuals with MID-BIF (McNally et al., 2021). In recent years, a
growing body of research has indicated that trauma treatment such as
eye movement desensitisation and reprocessing EMDR therapy is suitable,
safe and potentially effective for adults with MID-BIF diagnosed with PTSD
and/or comorbid behavioural and mental health problems (Penninx et al.,
2021; Verhagen et al., 2023).
Post-traumatic stress disorder unnoticed
Although PTSD is common among individuals with MID-BIF, it often
remains unnoticed in this target group (Kildahl et al., 2020a; Kildahl et al.,
2020b; Mevissen et al., 2020; Nieuwenhuis et al., 2019). For instance, in
Mevissen et al. (2020) study, among 106 adults with MID-BIF, the prevalence
of PTSD-diagnoses reported in the patients’ file was much lower (2%) than
the rate (38%) of PTSD that was found based on a standardised clinical
interview for PTSD. These and other studies suggest that PTSD is frequently
underdiagnosed in individuals with MID-BIF. It is likely that if PTSD is not
recognised, potentially effective trauma treatment will not be provided.
3
55]]></page><page Index="58" isMAC="true"><![CDATA[Chapter 3
Screening may help to identify PTSD in individuals with MID-BIF at an
early stage. Several trauma screeners based on the DSM-5-TR have been
developed and validated for individuals without MID-BIF. However, these
screeners have not been adapted or validated for people with MID-BIF. When
employing such questionnaires for individuals with MID-BIF, it is important
to make adjustments, including simplified language and supporting
visualization, to improve accessibility and comprehension (Kooijmans et
al., 2022). Until recently, a screening instrument for PTSD was not available
for individuals with MID-BIF.
The present study
For the purpose of developing a PTSD screener adapted to people with
MID-BIF, we adapted the Kinder en Jeugd Trauma Screener (KJTS; Kooij et
al., 2025) after permission from the KJTS research group. The language
level of the KJTS appears to be at the level that is also used in clinical work
with adults with MID-BIF. However further adaptations were necessary to
align the screener with the perspectives of individuals with MID-BIF (e.g.
some of the KJTS refers to school and not to work; see Methods section).
For example, the item content of the KJTS refers to parents and relatives
but not to professional caregivers. The KJTS consists of three parts. The
first part of the KJTS is based on the Clinical Administered PTSD Scale for
Children and Adolescents (CAPS-CA; Nader et al., 1996). Both the second
and third parts of the KJTS were developed using the Child and Adolescent
Trauma Screen (CATS-2; Sachser et al., 2022). There are two versions of
the KJTS: the self-report and caregiver report versions. Recent research
shows that the KJTS self-report version is valid and reliable in screening
for PTSD in children and adolescents (7–22 years old) in the general
population (Kooij et al., 2025). We adapted the KJTS self-report version
into the Trauma Screener-Intellectual Disability Adult version (TS-ID adult
version). The KJTS caregiver report version was adapted into the Trauma
Screener-Intellectual Disability Proxy version (TS-ID proxy version).
The purpose of the present study was to evaluate TS-ID by examining the
validity and reliability of both versions of the screener for use in adults with
MID-BIF. We also investigated which cut-off value of the TS-ID adult version
56]]></page><page Index="59" isMAC="true"><![CDATA[Development and evaluation of TS-ID
fits the optimal ratio of specificity to sensitivity in predicting diagnosis
according to a structured PTSD interview.
Methods
Participants and Setting
Adults with MID-BIF who were living in supported housing of two ID care
services in the Netherlands (‘s Heeren Loo and Trajectum) were informed
about the study by their treatment staff. The inclusion criteria were that
participants were diagnosed with MID or BIF, were at least 18 years old and
had sufficient Dutch language ability. The exclusion criteria were suicidality,
alcohol/drug use and use of serious sedating medications (e.g. anxiolytics).
Participation in this study was voluntary. All clients interested in participating
received an information letter. The study protocol received approval from
the Medical Research Ethics Committee, East Netherlands (reference
number: 2020-6967-NL75909.091.20). One hundred participants provided
written informed consent to participate in this study. For participants who
lacked the capacity to provide formal consent a legal representative was
asked to provide the consent.
Data were collected from 97 participants (three participants did not
complete the Diagnostic Interview Trauma and Stressors-Intellectual
disability [DITS-ID]). For five of the 97 participants, only the TS-ID adult
version was completed. For the remaining 92 participants, both the TS-
ID adult version and the TS-ID proxy version were completed. There were
55 women (57%) and 42 men (43%) between 18 and 73 years of age
(M = 32; SD = 14.1). IQ scores were available for 92 participants. The mean
IQ was 68 (range: 50–85; SD = 9.4). For five participants, no IQ scores were
found in their client files, but their files specified that they were diagnosed
with MID. Among 37 participants (38%), we found the presence of at least
one DSM-5 classification (American Psychiatric Association [APA], 2013)
in their client file: 20 participants (21%) had autism spectrum disorder, 11
(11%) attention deficit hyperactivity disorder (ADHD), seven (7%) PTSD,
three (3%) personality disorder, four (4%) mood disorder, and two (2%)
anxiety disorder. The 92 individuals who completed the TS-ID proxy version
3
57]]></page><page Index="60" isMAC="true"><![CDATA[Chapter 3
consisted of 73 professional caregivers, 11 fathers, five mothers, two
sisters and one brother.
Instruments
Child and Adolescent Trauma Screen
The Kinder en Jeugd Trauma Screener (KJTS; Kooij et al., 2025) is a trauma
screener for children and adolescents (7–22 years old). There are self-
report and caregiver report versions, each consisting of three sections. The
first section was a Dutch translation of the event section of the Clinical
Administered PTSD Scale Children and Adolescents (CAPS-CA; Nader et
al., 1996) and consists of a checklist of traumatic and stressful events (19
events in the child version and 20 events in the parent version), in which
participants can indicate whether they ever had experienced the event
by marking ‘Yes’ or ‘No’. The second section is a Dutch translation of the
symptom section of the Child and Adolescent Trauma Screen (CATS-2;
Sachser et al., 2022) and consists of a list of 20 questions that correspond
to the DSM-5-TR symptom criteria for PTSD. Each item can be scored on a
4-point Likert scale (0 = never, 1 = sometimes, 2 = often, 3 = almost always).
The third section is a Dutch translation of the impact and functioning
section of the Child and Adolescent Trauma Screen (CATS-2; Sachser et
al., 2022) and contains five questions about the impact of symptoms on
daily functioning, with response options: ‘Yes’ or ‘No’. The KJTS self-report
and KJTS caregiver report both have high internal consistency. Kooij et al.
(2025) found poor agreement between the self-report of the children and
adolescents and their caregivers. Area under the curve (AUC) of the KJTS
self-report was excellent compared to PTSD diagnosis using the CAPS-CA
(Kooij et al., 2025).
Development of the adult version of the Trauma Screener-Intellectual
Disability
The adult version of the Trauma Screener-Intellectual Disability (TS-ID adult
version) was adapted from the self-report version of the KJTS. Adjustments
were made based on input from the two focus groups and the clinical
expertise of the first and third authors on trauma and PTSD in adults with
MID-BIF. One focus group consisted of three adults with MID-BIF, and the
other consisted of four psychologists with extensive experience in the care
58]]></page><page Index="61" isMAC="true"><![CDATA[Development and evaluation of TS-ID
and treatment of adults with MID-BIF. In both focus groups, the TS-ID adult
version was presented to the participants, after which they were asked
what their overall impression was and what they thought of its coverage. As
a result, the instruction in part one of the TS-ID adult version was clarified,
and in this section, the wording of three original events were modified, such
as ‘placed out of home’ was changed into ‘placed out of home or placed
in crisis care’, and the wording of five events was simplified. For example,
‘dying of someone important to you’ was reworded into ‘death of someone
important to you’. The instructions for scoring the questions in part two
have also been clarified. The two questions in section three were modified
to better fit the participants. For example, ‘daycare’ was added to ‘school or
work’. Next, the TS-ID adult version was piloted with five adults with MID-BIF
in which the ‘think aloud’ method (Lundgrén-Laine & Salanterä, 2010) was
used to assess how they interpreted each question of the TS-ID. This was
done by asking participants to speak out when answering the questions.
The researcher observed carefully to determine whether the thought that
was spoken aloud corresponded to the content of the question and the
answer given. No further adjustments were made after pilot testing the
adult TS-ID version.
3
Development of the proxy version of the Trauma Screener-Intellectual
disability
The TS-ID proxy version is adapted from the KJTS caregiver report version.
We adapted the KJTS caregiver report version based on the input from two
focus groups and the clinical expertise of the first and third authors on trauma
and PTSD in adults with MID-BIF. Focus group one consisted of two parents
of adults with MID-BIF and focus group two consisted of two professional
caregivers who supported people with MID-BIF. Several adaptations were
made. In the adapted version the word ‘child’ has been replaced. For
example, ‘How often did your child suffer from the following feelings …’ has
been changed to ‘How often did the person you are completing this list for
suffer from the following feelings …’. The instructions in part one of the TS-
ID adult versions have been clarified. In this section, three new events are
added to the list of events and the three original events are expanded. For
example, ‘Experienced parents, or other family members hitting each other,
kicking, throwing objects, or destroying things’, which now also includes
59]]></page><page Index="62" isMAC="true"><![CDATA[Chapter 3
‘people from the living group’. Three phrases were simplified, such as ‘Left
alone for a long time or with other children without an adult around’, which
has been changed to ‘Left alone for a long time without an adult around’.
The instructions for scoring the questions in part two were also clarified.
Regarding section three, the same adjustments were made as in the TS-ID
adult version (see above). The TS-ID proxy version was piloted with two
professional caregivers and four parents of adults with MID-BIF, in which
also the ‘think aloud’ method was applied. No further changes were made
to the TS-ID proxy version after pilot testing.
Trauma Screener-Intellectual Disability
There are two versions of the TS-ID, a self-report version (TS-ID-adult
version) and a proxy version. The two versions of the TS-ID are identical in
content but differ in phrasing. The adult version is completed by the client,
while the proxy version is completed by a person who has regular contact
with the person with MID-BIF. Both the TS-ID adult version and TS-ID proxy
version contains three sections, with response options identical to those of
the KJTS. The first section of the TS-ID adult version and the TS-ID proxy
version consists of 22 and 23 events, respectively, in which a wide variety
of events are questioned: not only events that meet the A criterion but
also other negative life events. The proxy version of the TS-ID includes the
following additional event: ‘You have heard that the person for whom you
are completing this list, has been touched unwanted, but he/she denies it’.
Section two of both versions of the TS-ID consists of 20 PTSD symptoms
corresponding to the DSM-5-TR symptom criteria (cluster B: items 1–5,
cluster C: items 6–7, cluster D: items 8–14 and cluster E: items 15–20). The
total symptom frequency score (range: 0–60) can be obtained by summing
the scores of the 20 questions, in which questions 9, 10 and 15 are divided
into several sub-questions. For the latter questions, only the highest score
is recorded in the final score. The third section of both versions of the TS-ID
contains five questions about the impact of symptoms on daily functioning
with response options: ‘Yes’ or ‘No’.
Diagnostic Interview Trauma and Stressors-Intellectual Disability
The DITS-ID (Mevissen et al., 2018) is a clinical interview in which a PTSD
diagnosis can be established in adults with MID-BIF, based on the DSM-5
60]]></page><page Index="63" isMAC="true"><![CDATA[Development and evaluation of TS-ID
criteria. The protocol systematically evaluates DSM-criteria A, B, C, D, E, F,
G and H to determine whether an individual meets the criteria necessary
for PTSD diagnosis. The DITS-ID was developed for people with MID-BIF.
To facilitate accessibility, DITS-ID employs simplified language and visual
cues. DITS-ID consists of five sections. The first section consists of 31
questions on whether the participant had ever been exposed to a certain
event. If the answer is ‘Yes’, the interviewer asks ‘What happened?’ and
maps an event on a timeline. According to the answer, the interviewer
determines whether the event meets the A criterion of PTSD. The following
section includes 39 questions on PTSD symptoms, 32 of which correspond
to the DSM-5 symptom list (PTSD criteria B, C, D and E). In addition, four
potentially atypical symptoms (e.g. ‘Have you changed in terms of food
since the events?’. For example, that you eat too much or too little?) are
asked. Participants are requested to answer with ‘Yes’ or ‘No’, while the
‘Other’ category allows for answers such as ‘I don’t know’ or ‘I’ve always had
that’. Then a thermometer chart, which serves as a visual analogue, helps
participants to indicate the subjective degree of impairment in daily life on
a scale from 0 (totally not) to 8 (very much); a score of 4 or higher indicates
that the G criterion is met. If the G criterion is met, the participant is asked
to provide details about when the symptoms started, at what age and after
what event. This helps confirm whether the symptoms persist for more
than a month, which is a prerequisite for diagnosing PTSD (criterion F).
Finally, the interviewer assesses whether the symptoms can be attributed
to medication, drug use, other medical conditions or mental disorders
(criterion H). The DITS-ID has demonstrated good psychometric properties
in adults with MID-BIF. Internal consistency was high, interrater reliability
of the DITS-ID was good to excellent, and the construct and convergent
validity of the DITS-ID was good (Mevissen et al., 2020; Versluis et al., 2024).
In the present study, Cronbach’s alpha for the DITS-ID total score on the
symptom section (sum of ‘Yes’ scores) was .86, which indicates good
internal consistency.
Procedure
The data were collected between November 2021 and June 2022. Trained
master students of Radboud University and Vrije University Amsterdam,
and the first author administered the TS-ID adult and the DITS-ID to
3
61]]></page><page Index="64" isMAC="true"><![CDATA[Chapter 3
97 participants. For all three sections of the TS-ID adult version (i.e.
checklist on traumatic and stressful events, PTSD symptoms and impact
of the symptoms on daily life), participants first read the instructions
independently and were then asked, ‘Can you tell me what to do now?’.
If a participant could not read, all questions of the screener were read
out loudly. If the participant understood what he or she had to do, they
proceeded independently to complete the questions in the section. If the
participant did not understand what they should do, the instruction was
explained by the students or researcher after which they were asked again,
‘Can you tell me what to do now?’. If the participant still did not understand
what to do, the student or first author read the first three questions of
the section to the participant, after which the participant responded. If,
after the first three questions, the participant was still unable to continue
answering the questions independently, all questions in the section were
read aloud by the student or first author. Completing the TS-ID adult version
took approximately 10 minutes on average (M = 10.3; SD = 4.5). Help was
needed by 35 participants in the first part of the TS-ID adult version (i.e.
checklist on traumatic and stressful events), 57 participants needed help
in the second part (i.e. PTSD symptoms), and 45 participants needed help
in the third part (i.e. impact of the symptoms on daily life). After the TS-ID
adult version was completed, the DITS-ID was administered, which took
approximately 60 minutes on average. This order was chosen to represent
how the screener would be used in practice. The TS-ID proxy version was
completed by a person who had regular contact with each participant. This
person received the TS-ID proxy version from the researcher, asking to read
the questionnaire instructions carefully and then fill out the TS-ID proxy
version independently.
An expert meeting was held to establish a cut-off score for TS-ID. The group
of experts consisted of four psychologists specializing in the treatment and
care of adults with MID-BIF and (suspected) PTSD. Consensus was found
that the experts would rather have people wrongly screened positive as a
result of the TS-ID score than people wrongly screened negative and not
receive further diagnostic assessment of PTSD.
62]]></page><page Index="65" isMAC="true"><![CDATA[Development and evaluation of TS-ID
Analyses
To determine the reliability of the adult and proxy versions of the TS-ID, the
internal consistency of the total symptom frequency score (section two)
was calculated using Cronbach’s alpha (SPSS version 27). The validity of
the TS-ID adult version and TS-ID proxy version was assessed by comparing
the total symptom frequency score of both versions with the final outcome
of the DITS-ID (i.e. presence or absence of PTSD) using receiver operating
characteristic (ROC) analysis. The discriminative capacity of both versions
of the TS-ID was operationalised by calculating the AUC, which reflects their
ability to distinguish between individuals with and without PTSD. When an
optimal AUC value was obtained, we determined a cut-off point based
on the optimal ratio between sensitivity (justified positive prediction) and
1 − specificity (false-positive prediction). In addition, Youden’s J (Youden,
1950) was used as a supplementary evaluation to assess overall
discriminative power. Furthermore, the positive predictive value (PPV) and
negative predictive value (NPV) were calculated to provide additional insight
into the predictive accuracy of the different cut-off points. In determining
the cut-off score, explicit consideration was given to the outcomes of the
expert meeting of professionals who will use the TS-ID in clinical practice.
The number of participants required was calculated using the R package
for power calculation in diagnostic tests (Chernick & Liu, 2002; Chu & Cole,
2007; Flahault et al., 2005). Assuming a sensitivity and specificity of .8, an
estimated precision of .2 (delta .2), a significance level of .05 and a power of
.8 in a sample in which the distribution of yes/no PTSD is equally distributed
(prevalence .5), a total of 78 participants were needed. If more than 10% of
the questions in the DITS-ID, TS-ID adult version or TS-ID proxy version were
not scored, the questionnaire was not included in the analyses. Accordingly,
one TS-ID proxy questionnaire was excluded.
3
63]]></page><page Index="66" isMAC="true"><![CDATA[Chapter 3
Results
Descriptive statistics
Of the 97 participants, 56 (58%) met the criteria for PTSD using DITS-ID.
Of the individuals diagnosed with PTSD, 22 were male (39%), and 34 were
female (61%); 26 had MID (49%), and 27 had BIF (51%).
Validity and reliability of the Trauma Screener-Intellectual Disability adult
version
The validity of the TS-ID adult version was examined by calculating the
AUC using ROC analysis. The AUC was assessed by comparing the total
symptom frequency score of the TS-ID adult version with the outcome of
the DITS-ID (i.e. the presence/absence of PTSD). The AUC value was .94
(N = 97, SD = .03, p < .001). This indicates the excellent validity of the TS-ID
in distinguishing between individuals with and without a PTSD diagnosis
(see Figure 1).
Figure 1. ROC curve for the TS-ID adult total frequency score and final outcome of the DITS-ID (i.e.
yes or no PTSD).
64]]></page><page Index="67" isMAC="true"><![CDATA[Development and evaluation of TS-ID
Cronbach’s alpha for the total symptom frequency score (section two) of
the adult TS-ID version was .94, indicating high internal consistency.
Cut-off value of the Trauma Screener-Intellectual Disability adult version
Because the ROC analyses indicated excellent validity of the TS-ID adult
version in distinguishing individuals with and without a PTSD diagnosis,
a cut-off value was determined for the TS-ID adult version. Based on the
results depicted in Table 1, a cut-off score of 18 for the total symptom
frequency score of the adult TS-ID was the optimal threshold in accordance
with expert consensus, preferring a higher sensitivity at the expense of
specificity. A cut-off score of 18 achieved a sensitivity of 96% and specificity
of 83%, resulting in a Youden’s J index of 0.79, a PPV of 89% and a NPV
of 94%. Thus, sensitivity and specificity were in balance while diagnostic
accuracy was maximal.
3
Table 1. Sensitivity, specificity, Youden’s J, PPV and NPV for cut-off scores of the TS-ID adult total
score.
Cutoff score
TS-ID adult
1- Specificity PPV (%) Sensitivity Youden’s J NPV (%)
14 1.00 .71 0.71 82.4 100
15 .98 .78 0.76 85.9 97.0
16 .98 .78 0.76 85.9 97.0
17 .98 .80 0.79 87.3 97.1
18 .96 .83 0.79 88.5 94.4
19 .95 .83 0.78 88.3 91.9
20 .91 .85 0.77 89.5 87.5
21 .82 .88 0.70 90.2 78.3
22 .79 .88 0.66 89.8 75.0
23 .75 .88 0.63 89.4 72.0
24 .71 .93 0.64 93.0 70.4
25 .70 .93 0.62 92.9 69.1
26 .66 .92 0.59 92.5 66.7
27 .63 .95 0.58 94.6 65.0
28 .61 .95 0.56 94.4 63.9
29 .54 .98 0.51 96.8 60.6
30 .50 .98 0.48 96.6 58.8
Note. Bold represents the optimal cutt-off score.
65]]></page><page Index="68" isMAC="true"><![CDATA[Chapter 3
Validity and reliability of the Trauma Screener-Intellectual Disability
proxy version
The validity of the TS-ID proxy version was examined by calculating the AUC
using ROC analysis. AUC was assessed by comparing the total symptom
frequency score of the TS-ID proxy with the final outcome of the DITS-ID
(i.e. yes or no PTSD). The AUC value was .60 (N = 91, SD = .06, p = .10),
indicating low validity of the TS-ID proxy version for distinguishing between
individuals with and without a PTSD diagnosis. Cronbach›s alpha for the
total symptom frequency score of the TS-ID proxy version (section two)
was .93, indicating high internal consistency.
Because the ROC analyses indicated that the TS-ID proxy version is not a
valid instrument for detecting PTSD in people with MID-BIF, a cut-off value
was not determined for the TS-ID proxy version.
Discussion
The TS-ID adult version demonstrated high internal consistency and
excellent validity in distinguishing PTSD in adults with MID-BIF. A cut-off
value of 18 is recommended for the adult version of the TS-ID, with which
an optimal balance between sensitivity and specificity was achieved. While
demonstrating high internal consistency, the TS-ID proxy version did not
have significant validity in distinguishing individuals with and without a
PTSD diagnosis.
The effectiveness of the TS-ID proxy version in assessing adults with MID-
BIF may be limited by the lack of knowledge of parents (Kooij et al., 2025)
and professional caregivers regarding their trauma history (Hoogstad et
al., 2023). Furthermore, three of the four PTSD symptom clusters consist
of symptoms about thoughts and feelings as a result of experiencing a
traumatic event, that is, Intrusions (cluster B), Avoidance (cluster C) and
Negative alterations in cognitions and mood (cluster D). Adults with MID-
BIF communicate less clearly about their thoughts and feelings with their
caregivers (Hassiotis & Turk, 2012; Summers et al., 2017). Therefore, it
66]]></page><page Index="69" isMAC="true"><![CDATA[Development and evaluation of TS-ID
may not be surprising that the TS-ID proxy version did not demonstrate
significant validity in distinguishing individuals with and without a PTSD
diagnosis. This lack of validity underscores the limitations and challenges
of using proxy informants for screening for subjectively experienced
psychological symptoms, such as for PTSD (Webb et al., 2024).
In our study, a large proportion of the participants required assistance in
completing the TS-ID adult version. When assisting persons with MID-BIF
to complete self-reports, the nature of the contact between them and the
diagnostician can be a confounder, especially when sensitive topics are
addressed (Kooijmans et al., 2022). It remains unclear whether the assistance
from the master students and the main researcher has influenced clients’
responses and consequently affected the validity and cut-off value of the
TS-ID adult version. We have taken measures to reduce the influence: (1)
To determine if support was needed, we asked participants, after they had
read the TS-ID adult version instruction or after the instruction had been
read aloud, ‘Can you tell me what to do now?’ rather than ‘Do you know
what to do?’; (2) Pilot testing showed that participants could understand
the content of the questions; however, if not, we only provided instructions
on understanding the question and not on answering it.
Limitations of the study
This study has some limitations that should be considered. First, we
examined a specific sample of adults with MID-BIF living in supported
housing in the Netherlands, which may limit the generalisability of the
findings. Second, PTSD diagnosis was solely based on the DITS-ID rather
than on a comprehensive differential diagnostic assessment. Therefore,
the rate of PTSD in this sample should not be used as a clinical prevalence
estimate. Finally, one of the developers of the TS-ID was also involved in
collecting some of the data, which may have led to bias.
Recommendation for future research
The TS-ID version for adults is a new instrument, and future studies on the
screener should be conducted in various samples and settings, such as
outpatient care settings, forensic care and mental health settings, where
many people with MID-BIF receive care and treatment (Nieuwenhuis et
3
67]]></page><page Index="70" isMAC="true"><![CDATA[Chapter 3
al., 2019). It is recommended that a standardised written procedure be
developed to address commonly misunderstood items. Future research
should explore how to implement such procedures to support better
understanding without biasing the results. This could include investigating
which items are well or less well understood across different samples,
examining whether comprehension is related to verbal IQ or language skills
and determining the most effective method for assisting clients during
completion, such as reading items aloud versus using self-administration.
Like adults with MID-BIF, children with MID-BIF also have an increased risk
of experiencing many life events compared with children without MID-BIF
(Dion et al., 2018; McDonnell et al., 2019; Mevissen et al., 2016; Vervoort-
Schel et al., 2021). However, a screening tool for PTSD is not yet available
in children with MID-BIF. Future studies should adapt and evaluate trauma
screeners for children with MID-BIF so that PTSD can be better recognised
in children with MID-BIF.
Conclusion
Although adults with MID-BIF have an increased risk of developing PTSD,
PTSD is often not well recognised in these individuals (de Vogel & Didden,
2022; Mevissen et al., 2020; Nieuwenhuis et al., 2019). The adult TS-ID
version appears to be a promising screening instrument for recognising
PTSD in people with MID-BIF. Applying the TS-ID adult version appears likely
to reduce the risk of under-diagnosing PTSD and provide adults with MID-
BIF with the trauma treatment they need, which ultimately improves their
quality of life.
Acknowledgements
The authors thank the master’s students of Radboud University and Vrije
Universiteit Amsterdam for their assistance in data collection and all the
participants, family members and caregivers who participated in the study.
68]]></page><page Index="71" isMAC="true"><![CDATA[Development and evaluation of TS-ID
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70]]></page><page Index="73" isMAC="true"><![CDATA[]]></page><page Index="74" isMAC="true"><![CDATA[]]></page><page Index="75" isMAC="true"><![CDATA[Chapter 4
Brief intensive EMDR therapy
for PTSD in adults with
mild intellectual disability
or borderline intellectual
functioning and behavioural
problems: A multiple baseline
design study
This chapter was published as:
Versluis, A., de Jongh, A., Mevissen, L., Schuengel, C., Bakkum, L., &
Didden, R. (2025). Brief intensive EMDR therapy for PTSD in adults with
mild intellectual disability or borderline intellectual functioning and
behavioural problems: a multiple baseline design study.
European Journal of Psychotraumatology, 16(1), 2495642.]]></page><page Index="76" isMAC="true"><![CDATA[Chapter 4
Abstract
Background: Individuals with mild intellectual disability (MID; IQ 50–70)
or borderline intellectual functioning (BIF; IQ 70–85) are at an elevated
risk of post-traumatic stress disorder (PTSD), with PTSD symptoms
possibly associated with behavioural problems. It is important to test
the effectiveness of trauma-focused treatments, such as eye movement
desensitisation and reprocessing (EMDR) therapy, for adults with MID–BIF,
PTSD, and severe behavioural problems.
Objective: To determine the safety and effectiveness of brief intensive
EMDR therapy carried out by a team of rotating therapists in adults with
MID-BIF, PTSD, and severe behavioural problems.
Methods: Using a randomised non-concurrent multiple baseline between-
subjects design, 11 adults with MID-BIF, PTSD, and severe behavioural
problems received a maximum of 16 intensive EMDR sessions twice daily
for a maximum of two weeks from six different EMDR therapists. Primary
outcome measurements included severity of PTSD symptoms, PTSD
diagnostic status, and adverse events. Secondary outcome measurements
included the frequency and severity of behavioural problems, presence of
adaptive behaviour, and the use of involuntary care. Outcome measurements
were assessed at baseline, during the intervention and post-intervention
phases, and at the follow-up phases, and subject to randomisation tests for
statistical significance.
Results: Intensive EMDR therapy carried out by a team of rotating
therapists resulted in significant decreases in PTSD symptoms
(Mdifference = 15.84, p < .001) with nine of 11 participants no longer meeting
the PTSD diagnostic criteria immediately following treatment and at the
9-week follow-up. Randomisation tests revealed no significant changes
in adaptive behaviour, frequency, and severity of behavioural problems.
Additionally, no decrease in the use of involuntary care measures was
observed. One participant dropped out; no adverse events were observed.
Conclusions: Brief intensive EMDR therapy for individuals with MID-BIF and
severe behavioural problems, conducted by a team of rotating therapists,
can be done safely and effectively to reduce PTSD symptoms.
74]]></page><page Index="77" isMAC="true"><![CDATA[Brief intensive EMDR therapy for PTSD
Introduction
Individuals with mild intellectual disability or borderline intellectual
functioning (MID-BIF; IQ 50-85) may be at an increased risk of developing
post-traumatic stress disorder (PTSD) compared to the general population
(Mason-Roberts et al., 2018; Mevissen et al., 2020). This elevated risk can
be attributed to frequent exposure to traumatic events (McDonnell et al.,
2019; Nieuwenhuis et al., 2019) and difficulties in processing these events
owing to deficits in adaptive and cognitive functioning (Skelly, 2020). The
prevalence of PTSD in this group ranged from 10% to ≥40%, with higher
rates observed among individuals living in supported housing (Mevissen et
al., 2020; Versluis et al., 2025).
PTSD symptoms in individuals with MID-BIF are similar to those of
individuals without intellectual disabilities (Hoogstad et al., 2023; Mevissen
et al., 2020). Additionally, these symptoms overlap with behavioural
problems such as verbal or physical aggression (Kildahl & Helverschou,
2024; Rittmannsberger et al., 2020). Rittmannsberger et al. (2020) found
that the association between trauma exposure and challenging behaviour
in individuals with MID-BIF was mediated by the severity and frequency
of PTSD symptoms. Partly due to these behavioural problems, PTSD in
individuals with MID-BIF often remains undiagnosed (Kildahl et al., 2020)
and untreated (Keesler, 2020). Classifying people with PTSD requires
more than observing visible behaviour; it requires knowledge of what type
of events a person may have been exposed to, and how this is linked to
their current symptoms (American Psychiatric Association, 2022). Without
such a nuanced approach, individuals with MID-BIF may be directed
towards behaviour-based interventions. Such interventions may not treat
the underlying problems and when PTSD symptoms persist, restrictive
measures are sometimes used as a last resort (e.g. fixation and locked
doors) which may lead to more PTSD symptoms. Despite ongoing concerns
regarding the efficacy and quality of involuntary care for individuals with
intellectual disabilities (Heyvaert et al., 2014, 2015), these practices
remain prevalent (Bakkum et al., 2023; Fitton & Jones, 2020), especially
in individuals with severe behavioural problems (Hastings et al., 2013).
For example, Schippers et al. (2018a, 2018b) found that certain coercive
4
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measures were frequently taken, up to 43.6% (audio surveillance), 41.6%
(limited access to rooms/areas), and 33% (locking outer doors) for persons
residing in assisted living units for people with intellectual disabilities.
Trauma-focused therapeutic approaches such as eye movement
desensitisation and reprocessing (EMDR) therapy have shown promising
results for individuals in the general population (De Jongh et al., 2024).
However, the application of traditional treatments for PTSD in the general
population has been found to be associated with high dropout rates,
possibly due to symptom exacerbation, which can be challenging to
distinguish from the temporary distress inherent in trauma-focused therapy
(e.g. Bongaerts et al., 2022; Lewis et al., 2020; Van Woudenberg et al., 2018).
Between one-quarter and one-third of the participants undergoing trauma
treatment discontinued treatment, with some studies showing even higher
dropout rates (e.g. Niles et al., 2018). To address this issue, intensive trauma
treatments have been developed, involving multiple therapy sessions per
week or even multiple sessions per day, often with different therapists
rotating during sessions to maintain treatment intensity. Intensive trauma
treatments have been associated with improved therapeutic outcomes in
the general population (Hoppen et al., 2023), and these intensive treatments
have resulted in low dropout rates. For example, Van Woudenberg et al.
(2018) reported a dropout rate less than 3%, whereas Bongaerts et al.
(2022) achieved no dropout.
Although intensive trauma treatments have been shown to be effective
in children and adolescents with MID-BIF (Ooms-Evers et al., 2021), the
effectiveness of intensive EMDR therapy in adults with MID-BIF and severe
behavioural problems has not been investigated. Tests of suitable treatment
options, such as intensive EMDR therapy, for adults with MID-BIF and severe
behavioural problems are urgently needed for this vulnerable population.
The purpose of the present study was to determine the safety and
effectiveness of intensive EMDR therapy with a team of rotating therapists
in adults with MID-BIF and PTSD. We hypothesised that PTSD symptoms
and behavioural problems would significantly decline after treatment, and
that participants’ adaptive behaviour (i.e. behaviour in daily life, related to
PTSD symptoms, such as talking to strangers again; see Methods) would
improve, and these changes will persist at the 6-week, 9-week, and 4-month
76]]></page><page Index="79" isMAC="true"><![CDATA[Brief intensive EMDR therapy for PTSD
follow-ups. Additionally, we expect that most participants who met the
diagnostic criteria for PTSD at pre-treatment will lose their diagnostic status
post-treatment and that the intervention will reduce the use of involuntary
care in adults with MID-BIF. Furthermore, we expect that EMDR therapy will
not be associated with adverse events.
Methods
Design
A non-concurrent multiple baseline between-subjects design (Coon &
Rapp, 2018) was used to investigate the effectiveness of intensive EMDR
therapy with rotating therapists in 11 adults with MID-BIF and behavioural
problems on the severity of PTSD symptoms, PTSD diagnostic status,
adaptive behaviour, frequency and severity of behavioural problems,
and the use of involuntary care measures. The design contained 11
AB (A = baseline phase; B = post-intervention phase and follow-up
measurements) experiments in which participants were randomly assigned
to baseline lengths of five, six or seven weeks. The person conducting
the randomisation was masked to participants’ identity. The intervention
phase consisted of a maximum of two weeks, during which EMDR therapy
was administered eight times a week from Monday to Thursday. After the
completion of EMDR therapy, there was a three-week post-intervention
phase, followed by three follow-up measurements (six weeks, nine weeks
and four months after the intervention).
Participants and setting
Adults with MID-BIF (IQ 50-85) living in supported housing of an ID care
service in the Netherlands (‘s Heeren Loo) who were on the waiting list for
EMDR therapy were informed of the study by the first author. The inclusion
criteria were that the participants were diagnosed with MID or BIF, were
at least 18 years old, met the DSM-5-TR diagnostic criteria for PTSD, had
severe behavioural problems classified as Care Intensity Level (in Dutch:
Zorg Zwaarte Pakket; ZZP) 7, which represents eligibility for the highest
level of care intensity according to the Dutch healthcare authority, indicating
the need for intensive support due to severe behavioural problems as
described in their client files), and had sufficient Dutch language ability.
4
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Each participant had at least one steady professional caregiver involved
during the study period. The exclusion criteria were high suicidal risk and
excessive alcohol/drug use which would make it difficult for a participant
to attend a therapy sober.
Participation in this study was voluntary. The study protocol was approved by
the Medical Research Ethics Committee of the East Netherlands (reference
number: 2020-6967- NL75909.091.20). All clients interested in participating
in the study received an information letter. Nine participants provided
written informed consent to participate in this study. Because of a lack of
capacity to provide written consent, legal representatives provided consent
for three participants. However, these three participants still provided
verbal consent. This resulted in an initial sample of 12 participants. One
participant dropped out on the second day of EMDR therapy because he felt
overwhelmed by the emotional stress and refused to further participate in
this study. Six women and five men aged 21–65 years, participated in this
study. Table 1 presents the characteristics of the participants.
Measures
In this study, the primary and secondary outcome measurements were
assessed. The frequencies used for these measurements are listed
in Table 2. The descriptive statistics of the outcome measurements are
listed in Table 3.
Table 2. Overview of Measurements by Phase and Frequency
Measurement Participants’ Safety (electronic client file) PTSD symptoms (TS-ID) PTSD classification (DITS-ID) Adaptive behaviour (GAS) Behavioural problems (BPI) Involuntary care (electronic client file) Frequency
Extracted by phase
Twice weekly during all phases and follow-ups
First week of baseline, first and last days of
intervention, last week of post-intervention, and
three follow-ups
Daily (morning and afternoon) during all phases and
follow-ups
Once weekly during all phases and follow-ups
Extracted by phase
Note. DITS-ID = Diagnostic Interview Trauma and Stressors – Intellectual Disability Adult Version;
TS-ID = Trauma Screener – Intellectual Disability; GAS = Goal Attainment Scaling; BPI = Behavior
Problems Inventory.
78]]></page><page Index="81" isMAC="true"><![CDATA[Table 1. Participant characteristics, treated events, and number of sessions.
Participant Sex Age
category
DSM diagnoses / syndrome
(other than PTSD or MID-BIF)
IQ EMDR therapy
before
Treated traumatic and stressful memories
(number of memories treated)
Number of
sessions
1 Male 30-35 Other DSM diagnosis TIQ: 61
No 2 Female 20-25 Other DSM diagnoses and
syndrome
3 Male 25-30 Other DSM diagnosis and
syndrome
VCI: 66
PRI: 81
WMI: 55
PSI: 48
TIQ: 65
PIQ: 50
VIQ: 65
TIQ: 79
VCI: 79
PRI: 98
WMI: 77
PSI: 81
Placed out of home (1)
15
Bullied (2)
Aggression in living environment (6)
Parents divorced (1)
Verbal aggression at home (1)
Sexual violence (1) 16
Yes, but
therapy not
completed
No 4 Male 25-30 Other DSM diagnosis TIQ: 69 Yes, but there
are untreated
traumatic
or stressful
events.
5 Female 40-45 No other DSM diagnosis or
syndrome
TIQ: 69
PIQ: 70
VIQ: 68
No Seen unpleasant images on social media
(1)
Bullied (2)
Victim of aggression on the street (1)
Dead pet (1)
Returning nightmare (1)
Police related incidents (2)
Domestic violence (2)
Bullied (1)
Sexual violence (1)
Involuntary care (1)
Severe storm (1)
Parents divorced (1)
Verbal aggression at home (2)
Witnessed (traffic) accident (1)
Illness of a family member (1)
Domestic violence (2)
Bullied (2)
Sexual violence (1)
Verbal aggression at home (1)
Dead pet (1)
Serious physical injury (2)
9
16
16
Brief intensive EMDR therapy for PTSD
79
4]]></page><page Index="82" isMAC="true"><![CDATA[80
Participant Sex Age
category
Table 1. continued.
6 Female 35-40 No other DSM diagnosis or
syndrome
DSM diagnoses / syndrome
(other than PTSD or MID-BIF)
IQ EMDR therapy
before
7 Female 25-30 No other DSM diagnosis or
syndrome
- Yes, but there
are untreated
traumatic
or stressful
events.
TIQ: 50 Yes, but
therapy not
completed.
8 Female 25-30 No other DSM diagnosis or
syndrome
TIQ: 50 No 9 Male 65-70 Other DSM diagnosis TIQ: 56
No PIQ: 50
VIQ: 58
Treated traumatic and stressful memories
(number of memories treated)
Number of
sessions
Illness of a family member (1)
Placed out of home/ to a crisis location (1)
Domestic violence (1)
Sexual violence (2)
Parents divorced (1)
Witnessed (traffic) accident (1)
Serious physical injury (1)
Natural death of relative (1)
Not taken seriously (1)
Placed out of home (1)
Domestic violence (3)
Sexual violence (1)
Parents divorced (1)
Involvement in drug trafficking (2)
verbal aggression at home (3)
Mother arrested (1)
Forced by mother to steal money (1)
Illness of a family member (1)
Domestic violence (2)
Sexual violence (1)
Dead pet (1)
Seeing mother cut herself (1)
Illness of a family member (1)
Natural death of relative (3)
Not taken seriously*
Placed out of home (1)
Domestic violence*
Bullied*
Sexual violence (1)
Aggression in the residential group*
Involuntary care (1)
Been in prison (1)
Parents divorced (1)
Accused of sexual abuse (1)
Girlfriend breaks up (1)
11
12
12
13
Chapter 4]]></page><page Index="83" isMAC="true"><![CDATA[81
Table 1. continued.
Participant Sex Age
category
DSM diagnoses / syndrome
(other than PTSD or MID-BIF)
IQ EMDR therapy
before
Treated traumatic and stressful memories
(number of memories treated)
Number of
sessions
10 Female 40-45 Other DSM diagnoses TIQ: 61
PIQ: 64
VIQ: 58
11 Male 20-25 Other DSM diagnosis TIQ: 65
PIQ: 73
VIQ: 63
No Domestic violence (2)
Bullied (3)
Sexual violence (2)
Aggression in the residential group (3)
Involuntary care (3)
Been in prison (1)
Epileptic seizure (1)
Hearing of voices (1)
Severe storm (1)
Medical procedure (1)
No Illness of a family member (1)
Natural death of relative (1)
Not given enough attention (1)
Not taken seriously (3)
Placed out of home (1)
Placed to crisis location (1)
Seen unpleasant images (2)
Domestic violence (3)
Bullied (1)
Seen a burning house (1)
Arrested by the police (1)
Victim of aggression on the street (2)
11
11
Note. TIQ = Total IQ; VCI = Verbal Comprehension Index; PRI = Perceptual Reasoning Index; WMI = Working Memory Index; PSI = Processing Speed Index; PIQ
= Perceptual IQ; VIQ = Verbal IQ.
* There are no details regarding the number of different memories processed.
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Table 3. Descriptive Statistics
Outcome n M Note. n = total number of measurements.
SD
PTSD symptoms (TS-ID) 257 25.67 15.98
Adaptive behaviour (GAS) 1164 6.08 77.28
Behavioural problems (BPI) - frequency 152 12.46 11.43
Behavioural problems (BPI) - severity 149 11.51 12.00
Primary outcome measures
PTSD symptoms
The symptom section of the self-report measure Trauma Screener –
Intellectual Disability (TS-ID; Versluis et al., 2025) was used to assess PTSD
symptoms. This section consists of 20 questions scored on a 4-point Likert
scale (0 = never, 1 = sometimes, 2 = often, 3 = almost always). The total
symptom frequency score (range 0-60) was obtained by summing the
scores of the 20 questions, in which questions 9, 10, and 15 were divided
into several sub-questions. For the latter questions, only the highest score
was recorded in the final score. Higher scores indicate greater levels of
PTSD symptoms. The TS-ID has good psychometric properties, including
high internal consistency and excellent validity for distinguishing PTSD
in adults with MID-BIF based on the outcomes of the DITS-ID (Versluis et
al., 2024). Participants completed the symptom questions of the TS-ID, with
the DITS-ID timeline (see DITS-ID) placed next to the TS-ID, which provided
a clear visual cue for the (traumatic and stressful) events. A professional
caregiver was present to explain the items of the TS-ID if needed.
DSM-5-TR PTSD diagnostic status
PTSD diagnostic status was assessed using the Diagnostic Interview Trauma
and Stressors – Intellectual Disability – Adult Version (DITS-ID; Mevissen
et al., 2018). This clinical interview takes approximately 45–60 minutes to
complete and is used to classify DSM-5-TR PTSD. The first section consists
of 31 questions (yes/no/other) regarding Type A and stressful life events
(not meeting the A-criterion but are experienced negatively by the person).
The symptom section includes 39 PTSD symptom questions (PTSD criteria
B, C, D, and E) and four questions on potential atypical trauma symptoms
(yes/no/other). Subsequently, a thermometer card is used to support the
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person in indicating impairment in daily life on a scale from 0 (totally not)
to 8 (very much). If the interference score is four or higher (criterion G), the
participant is asked when the symptoms started to confirm if they have
been present for over a month (criterion F). Finally, the interviewer checks if
the symptoms are not due to medication, drug use, medical conditions, or
somatic disorders (criterion H). There are several versions of the DITS-ID.
This study used the adult version and follow-up measurements, which takes
approximately 15 min. First, the participant is asked whether the participant
has experienced a traumatic or stressful event since the last DITS-ID
administration, followed by symptom questions and the thermometer
card. The DITS-ID adult version has good psychometric properties, with
high internal consistency, good-to-excellent interrater reliability, and good
construct validity (Mevissen et al., 2020; Versluis et al., 2024). All DITS-ID
interviews were conducted by trained master’s students and an independent
psychologist.
Participants’ safety
The safety of the participants was defined as the absence of adverse events,
including increased suicidal ideation or being placed in a crisis intervention
facility. All recorded adverse events were extracted from the participants’
electronic client files.
4
Secondary outcome measures
Adaptive behaviour
Goal Attainment Scaling (GAS) was used to monitor adaptive behaviour
on a 6-point scale (−3 = regression, – 2 = initial situation, – 1 = less than
the target, 0 = target, + 1 = more than the target, + 2 = much more than
the target). Adaptive behaviour was defined in agreement with the
participant, professional caregiver, and their psychologist and focused on
(for the professional caregiver) observable behaviours that the participant
was expected to be capable of without PTSD. Adaptive behaviour was
determined for each participant prior to EMDR therapy, and professional
caregivers scored the GAS scale daily (twice a day, in the morning and
afternoon).
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Behavioural problems
The Behavior Problems Inventory (BPI; Rojahn et al., 2001) indexes the
frequency and severity of a problem behaviour. Both the frequency and
severity scores can be derived from the total BPI score. The frequency
score of the problem behaviour (51 items) was measured on a 5-point
Likert scale (0 = never, 1 = monthly, 2 = weekly, 3 = daily, and 4 = hourly).
The severity score of the problem behaviour (51 items) was measured on
a 3-point Likert scale (1 = mild problem, 2 = moderate problem, 3 = severe
problem). Total scores for both frequency and severity were calculated, with
higher scores denoting more frequency/severity of problematic behaviour.
In our study, we used the Dutch version of the BPI, which has adequate to
good psychometric properties including good inter-rater, intra-rater, internal
consistency, and convergent validity (Dumont et al., 2014). A professional
caregiver who had regular contact with the participants completed the BPI.
Involuntary care
Involuntary care measures is defined as: ‘Any care opposed by a client or
client-representative’ (Staatsblad, 2018) and were recorded by professional
caregivers of the participants in the ‘Involuntary care reporting system’ in
clients’ electronic files. This system was documented for each participant,
and both predetermined (multidisciplinary agreed) involuntary care (e.g.
‘bedroom door locked at night’) and incidents of involuntary care (e.g. ‘fixation
by professional caregivers’). A study by Schippers et al. (2018a, 2018b) on
the ‘Involuntary Care Reporting System’ of ‘s Heeren Loo demonstrated that
involuntary care could be reliably recorded with this system. All recorded
involuntary care was extracted from participants’ electronic client files.
Intensive EMDR-therapy and procedure
The participants received EMDR therapy twice daily for a maximum of two
weeks from six therapists. Three therapists were certified ‘EMDR Europe
practitioners’, while the other three had completed the basic and advanced
EMDR courses accredited by the Dutch EMDR Association. All therapists
had treated at least 20 clients with MID-BIF for PTSD before the start of
the study. The authors were not involved as therapists in the current study.
Treatment integrity was monitored by the first author and an accredited
supervisor from the Dutch EMDR Association (third author) through three
supervision sessions during the baseline phase and three supervision
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sessions during the intervention phase. These sessions involved reviewing
the video recordings and discussing the cases to ensure adherence to the
treatment protocol.
A week before therapy (baseline), the professional caregivers and, if
possible, the client’s relative received psychoeducation about PTSD and
EMDR therapy. Therapy sessions were conducted twice daily (morning
and afternoon) from Monday to Thursday, over a two-week period. During
the first therapy session (60 min), a case conceptualisation based on the
timeline of the DITS-ID was established. For this case conceptualisation, all
traumatic (meeting A-criterion) and stressful events (not meeting A-criterion)
on the timeline were assessed for distress using a scale for the Subjective
Units of Disturbance (SUD) 0 = no distress to 10 = extreme distress and
were ordered from high to low SUD. This resulted in a list of traumatic and
stressful events that could be treated (case conceptualisation). The first
therapy session included psychoeducation for participants about PTSD
and EMDR therapy. Participants were not trained in the use of coping skills
or emotion regulation techniques prior to treatment (De Jongh et al., 2016).
After the first session, all subsequent sessions consisted of 60 min of EMDR
therapy. We used the EMDR therapy protocol for children and adolescents
up to 18 years of age (De Roos et al., 2021). This protocol includes the
same eight phases as the standard protocol developed by Shapiro (2018)
but is adapted for individuals with lower language skills, such as individuals
with MID-BIF. If necessary, cognitive interweaves were applied as described
by Shapiro (2018). In line with the working memory theory (see De Jongh et
al., 2024, for a review), working memory taxation during EMDR therapy was
achieved using several tasks, specifically eye movements (following fingers
or a light bar), which were combined with pulsators. If the participant was
unable to perform eye movements, an additional distracting task, such as
tapping, counting, or a simple calculation task, was added. These tasks
were also added when the SUD score remained high (Matthijssen et
al., 2021). Once a memory was successfully processed, it was checked off
on the case conceptualisation with the participant, and the therapy moved
to the next traumatic event. Therapy was completed after all memories
of case conceptualisation were processed. The treatment duration varied
depending on the number of traumatic events and the time required for the
processing of traumatic memories.
4
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Statistical analyses
All analyses were conducted in R (R Core Team, 2023, version 4.3.2) and
RStudio (Posit, 2024, version 2024.09.0). To determine the required sample
size, we calculated the number of permutations for this non-concurrent
multiple baseline between-subject design. For a robust randomisation test,
the number of possible starting points (k) must exceed 20, ensuring 1/k
(p < .05; Bulté & Onghena, 2009). With 11 participants and three starting
points, our study yielded 177 randomisation possibilities, resulting in 1/177
(p < .001), ensuring sufficient statistical power. To assess the test-retest
reliability within the baseline phase, the (Intraclass Correlation Coefficient;
ICC; Koo & Li, 2016) using a one-way random effects model to measure
consistency, was calculated for the BPI, TS-ID, and GAS.
To calculate the non-overlap of all pairs (NAP) for TS-ID, GAS, and BPI for
each participant, the SingleCaseES package (Pustejovsky et al., 2024) was
used. For the TS-ID and BPI, an improvement in symptoms was indicated
by a decrease in scores, and for the GAS, an improvement was indicated by
an increase. The baseline (phase A) was compared to the post-intervention
and follow-up phases (phase B). Missing values were excluded from the
analysis. The effect size was assessed based on the guidelines of Parker
and Vannest (2009).
Group-level randomisation tests were performed for the TS-ID, GAS, and BPI
(total and subscales) scores with the scan package (Wilbert & Luke, 2023)
to compare the baseline (phase A) with the post-intervention and follow-
up phases (phase B) using a t-statistic to measure phase differences.
Randomisation tests were conducted using the distributions of the data
based on random samples of n = 177 possible permutations. Missing
values were interpolated prior to analysis.
PTSD symptom frequency scores (TS-ID) were plotted for visual analysis
using the scplot package (Wilbert, 2023). PTSD diagnostic status (DITS-
ID) was visually analysed using a table. The use of involuntary care was
documented and described in the results section.
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Results
Eleven participants engaged in an average of 13 therapy sessions
(range = 9-16). On average, participants had experienced 12 traumatic
and stressful events at the start of the study, and at the end of the study,
ten participants had processed all of their traumatic and stressful events
(SUD = 0). Table 1 provides a summary of the number of therapy sessions
attended by each participant, along with the stressful and traumatic events
treated during therapy. The ICC for the baseline TS-ID total frequency scores
was .97, for the BPI total frequency scores .94, for the BPI total severity
scores .95, and for the GAS scores .92, all indicating high reliability of the
measurements (p < .01).
Primary outcome measures
PTSD symptoms
Figure 1 illustrate the visual analysis of PTSD symptom frequency scores
(TS-ID) throughout the study. The NAP values of the TS-ID scores of
individual participants indicated four participants with medium and seven
participants with large differences between the A and B phases (see Table
4). The randomisation test showed a statistically significant group-level
effect (observed Mdifference = 15.84, p < .01).
Table 4. NAP Values for TS-ID Total Frequency Scores.
4
Participant NAP SE Effect size category
1 .92 .07 Medium
2 .79 .10 Medium
3 .87 .09 Medium
4 .99 .01 Large
5 1.00 .01 Large
6 .95 .05 Large
7 .84 .09 Medium
8 .98 .02 Large
9 1.00 .01 Large
10 1.00 .01 Large
11 1.00 .01 Large
Note. NAP = non-overlap of all pairs; TS-ID = Trauma Screener Intellectual Disability; SE = standard
error.
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Figure 1. Visual Analysis of TS-ID Frequency Scores.
Note. Participants are ordered according to the baseline lengths. A = baseline; I = intervention; B =
post-intervention and follow-up. A = baseline; I = intervention; B = post-intervention and follow-up.
88]]></page><page Index="91" isMAC="true"><![CDATA[Brief intensive EMDR therapy for PTSD
DSM-5-TR PTSD diagnostic status
Table 5 presents the DSM-5-TR PTSD diagnostic status per participants
by different phases. Among the 11 participants, nine no longer met the
diagnostic criteria for PTSD one week after the start of treatment. Participant
8 was reclassified as having PTSD at the first follow-up measurement,
but this classification was no longer present at the second follow-up. In
participants 2 and 5, the PTSD classification persisted throughout the study.
Table 5. DSM-5-TR PTSD classification (DITS-ID).
Phase P1 P2 P3 P4 P5 P6 P7 Baseline start Baseline end Intervention Post-intervention Follow-up I Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
No Yes No No Yes No No No No No No
No Yes No No Yes No No No No No No
No Yes No No yes No No Yes No No No
Follow-up II No Yes- No - No No No No No No
Follow-up III No Yes - No - No No No No No No
P8 P9 P10 P11
Note. P = participant; baseline start = start baseline; baseline end = end baseline; intervention
= after one week of treatment; post-intervention = three weeks after treatment; follow-up I = six
weeks after intervention; follow-up II = nine weeks after intervention; follow-up III = four month
after intervention.
Participants’ safety
One participant stayed in a crisis shelter during the baseline and intervention
phases but actively participated in the therapy. After the intervention,
he returned home. Crisis placement was considered unrelated to the
intervention, as confirmed by both the participant and the professional
caregiver. No other adverse events were reported in the participants’
electronic records.
4
Secondary outcome measures
Adaptive behaviour
The NAP values for the GAS scores indicated that the differences
between A and B ranged from a weak effect to medium and one large
effect (Table 6). The randomisation test was not statistically significant
(observed Mdifference = 8.81, p = .712). Participant 1 was excluded from both
analyses due to too many missing values (87%).
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Table 6. NAP Values for GAS and BPI scores.
GAS
Scaling scores
BPI Total
frequency score
BPI Total
severity score
Participant NAP SE NAP SE NAP SE Effect
size
category
Effect
size
category
Effect
size
category
1 -- -- -- .47 .19 Weak .42 .21 Weak
2 0.53 0.06 Weak .19 .13 Weak .25 .15 Weak
3 1.00 0.01 Large .58 .20 Weak .60 .19 Weak
4 0.57 0.08 Weak .60 .18 Weak .58 .18 Weak
5 0.92 0.05 Medium .70 .17 Medium .62 .20 Weak
6 0.62 0.06 Weak .87 .10 Medium .93 .06 Large
7 0.79 0.03 Medium .68 .15 Medium .68 .15 Medium
8 0.88 0.04 Medium .36 .18 Weak .38 .18 Weak
9 0.54 0.07 Weak .67 .20 Medium .60 .19 Weak
10 0.44 0.05 Weak .74 .13 Medium .66 .19 Medium
11 0.42 0.06 Weak .53 .21 Weak .58 .20 Weak
Note. NAP = non-overlap of all pairs; GAS = Goal Attainment Scaling; SE = standard error; BPI = Brief
Problem Inventory; NAP values for participant 1, GAS scores could not be calculated because too
many values were missing (87%).
Behavioural problems
The NAP values for the BPI total frequency and severity scores indicate that the
differences between A and B range from mainly weak effects to medium and
(one) large effects (see Table 6). Randomisation tests were not statistically
significant for the total frequency (observed Mdifference = 0.80, p = .407) and the
total severity of behavioural problems (observed Mdifference = 0.73, p = .367).
Involuntary care
For one participant, one extra case of predetermined (multidisciplinary)
involuntary care (off-label psychopharmacological medication) was
recorded by professional caregivers of the participant during the intervention
phase compared to the baseline. Another participant experienced one
incident of involuntary care, recorded by the professional caregiver, during
the follow-up phase. No other changes in recorded involuntary care
measures or incidents of involuntary care were recorded.
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Discussion
The results demonstrated a significant reduction in PTSD symptoms, with
nine out of 11 participants no longer meeting the PTSD diagnostic criteria
post-intervention. These improvements were maintained at both the 9-week
and 4-month follow-ups, indicating the sustained efficacy of intensive EMDR
therapy in this population. These findings align with previous research on
intensive trauma therapy in children and adolescents with MID-BIF and
PTSD (Ooms-Evers et al., 2021). Importantly, the intervention showed no
adverse events, underscoring its safety.
Only one participant discontinued therapy. This is consistent with the low
dropout rates consistently reported in intensive trauma-focused treatment
programs (for example, Bongaerts et al., 2022; Voorendonk et al., 2023)
in the general population. The intensive format, with frequent scheduled
sessions has been found to be capable of reducing avoidance behaviour
and fostering greater engagement (Hendriks et al., 2018; Szafranski et
al., 2017).
The outcomes for adaptive behaviour indicated improvements in some
participants, whereas others exhibited less noticeable changes. Meaningful
changes in adaptive behaviour may require direct, targeted intervention
aimed at learning new skills and adapting the environment. For example,
adaptive behaviour, such as ‘the participant independently walking home
from work’, may be facilitated by a reduction in PTSD symptoms, but the
ongoing involvement of professional caregivers may result in the caregivers
continuing walking alongside the individual, preventing actual improvement
in adaptive behaviour in the participant.
Some participants showed minimal change in behavioural problems,
whereas others showed weak improvement. In addition, no change
(meaning no increase and no decrease) in involuntary care measures
were observed, which could be attributed to the continued presence of
behavioural problems. Although brief tracks of trauma-focused treatment
have generally been found to reduce the severity of PTSD symptoms
(Hoppen et al., 2023; Voorendonk et al., 2023), this may not necessarily
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translate into changes in behavioural problems (Cuijpers et al., 2020).
Because the focus of EMDR therapy is on reducing PTSD symptoms
by processing participants’ traumatic memories rather than targeting
behavioural problems, the ability to directly address these problems may
be limited. There is presently limited research on the association between
behavioural problems and PTSD symptoms in individuals with MID-BIF.
The current findings suggest that intensive trauma treatment is feasible
and effective despite severe behavioural problems. Further research is
needed to assess whether intensive trauma treatment may augment the
effectiveness of interventions to reduce behavioural problems or vice
versa. Alternatively, trauma treatment and behavioural interventions may
reach their effects independently from each other and may enhance quality
of life also independently.
Study limitations
First, although the randomised non-concurrent multiple baseline design
offers robust insights, it does not provide information on which subgroups
within the MID-BIF population benefit more or less from the intervention.
Second, the PTSD classification was not measured repeatedly across the
different study phases, which prevented us from measuring a statistically
significant loss of PTSD diagnostic status. A third limitation is the potential
selection bias due to loss to follow-up measurements. The design used
in the current study does not account for this bias, as not all participants
were included in the analyses, which may have affected the validity and
generalisability of the results. Fourth, we investigated a specific sample of
adults with MID-BIF, all living in supported housing in one Dutch ID care
service. Further research is needed to determine whether the observed
effects can be replicated in more diverse or larger samples, which would
enhance the applicability of these treatment approaches across various
clinical contexts.
Conclusion
In conclusion, the results of this study support the efficacy and safety
of intensive EMDR therapy using a rotating team of therapists to reduce
PTSD symptoms among adults with MID-BIF and behavioural problems.
Although the treatment demonstrated significant improvements in PTSD
92]]></page><page Index="95" isMAC="true"><![CDATA[Brief intensive EMDR therapy for PTSD
symptoms, the effects on adaptive behaviour and behavioural problems
were more variable, suggesting the need for further research to explore
complementary approaches. Despite the small sample size, our results
provide valuable insights and clinical implications for offering accessible
trauma therapy to this population implicating that severe behavioural
problems may not necessarily be a contraindication for intensive trauma
treatment in individuals with MID-BIF.
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Brief Intensive EMDR therapy
with rotating therapists:
Experiences of adults with
mild intellectual disability
or borderline intellectual
functioning, PTSD, and severe
behavioural problems
This chapter was published as:
Versluis, A., Peters-Scheffer, N., Schuengel, C., Mevissen, L., de Jongh, A.,
& Didden, R. (2025). Brief intensive EMDR therapy with rotating therapists:
Experiences of adults with mild intellectual disability or borderline
intellectual functioning, PTSD, and severe behavioural problems. European
Journal of Trauma & Dissociation, 9, 100610.]]></page><page Index="102" isMAC="true"><![CDATA[Chapter 5
Abstract
Background: This study explored the experiences of individuals with mild
intellectual disability (MID: IQ 50-70) or borderline intellectual functioning
(BIF: IQ 70-85), post-traumatic stress disorder (PTSD), and severe
behavioural problems, with brief Intensive EMDR therapy delivered by a
team of rotating therapists.
Purpose: Preliminary research indicates that Intensive EMDR therapy with
a team of rotating therapists is effective in treating PTSD in individuals with
MID-BIF. To optimise treatment outcomes, it is important to understand
how they experience this treatment format.
Methods: In-depth semi-structured interviews were conducted with three
adults with MID-BIF and severe behavioural problems, before and after
therapy. Interviews with three professional caregivers (before and after
therapy), three EMDR therapists (after therapy), and field notes were used
to contextualise the experiences of the participants.
Results: Interpretative phenomenological analysis (IPA) revealed that
participants started Intensive EMDR therapy with rotating therapists holding
high expectations. One participant discontinued early, two completed
treatment, and all reported positive experiences with both the intensive
format and therapist rotation model. The intensity was seen to support
continuity and engagement, particularly compared to weekly therapy
sessions. Minimal involvement of the (professional) support systems was
also observed.
Conclusions: Participants with MID-BIF and severe behavioural problems
generally reported positive experiences with brief Intensive EMDR therapy
delivered by a team of rotating therapists.
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Introduction
Individuals with mild intellectual disability (MID; IQ 50-70) or borderline
intellectual functioning (BIF; IQ 70-85) may be at a higher risk of developing
post-traumatic stress disorder (PTSD) compared to the general population
(Mason-Roberts et al., 2018; Nieuwenhuis et al., 2019; Versluis et al.,
2025b). The prevalence of PTSD in this group ranges from 10% to 40%, with
higher rates reported among those living in supported housing (Mevissen
et al., 2020a; Versluis et al., 2025b). Frequent exposure to traumatic
events (McDonnel et al., 2019; Nieuwenhuis et al., 2019) and difficulties
in processing these events owing to deficits in adaptive and cognitive
functioning (Skelly, 2020) can be attributed to this elevated risk.
Although PTSD has an acute onset, its recovery can run a protracted course.
Treatments that only require a brief period to work are therefore particularly
helpful. Preliminary research indicates that Intensive EMDR therapy with a
team of rotating therapists is effective in treating PTSD in adults with MID-
BIF (Versluis et al., 2025a). To optimise treatment outcomes, it is important
to understand how clients experience this treatment format.
EMDR for individuals with MID-BIF
EMDR therapy is an eight-phase, structured therapy aimed at resolving
symptoms resulting from traumatic memories (Shapiro, 2018). EMDR is
currently the most extensively studied PTSD treatment among individuals
with MID-BIF, and findings suggest that it is a safe, feasible, and potentially
effective therapy for this group (e.g., Byrne et al., 2020; Penninx Quevedo
et al., 2021; Verhagen et al., 2023). For most of these studies, the EMDR
protocol for children and adolescents up to 18 years of age (De Roos et al.,
2021) was applied, which is adapted for individuals with lower language
skills and has proven to be suitable and potentially effective for individuals
with MID-BIF (Byrne et al., 2020; Penninx et al., 2021; Schipper-Eindhoven
et al., 2024; Verhagen et al., 2023). This protocol includes the same eight
phases as the standard protocol developed by Shapiro (2018).
Schipper-Eindhoven et al. (2024) conducted a systematic review of 13
studies to identify and categorise the difficulties therapists face when
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applying EMDR therapy to individuals with MID-BIF and the adaptations
used to overcome these difficulties. They divided the adaptations made into
three main categories: EMDR delivery (e.g., tuning to the developmental level
of the client, simplifying language, decreasing pace), involvement of others
(e.g., involving family or support staff during or in between sessions), and
the therapeutic relationship (e.g., taking more time, adopting a supportive
attitude).
Intensive trauma treatment
Intensive trauma treatment can be an effective alternative to weekly
treatment for PTSD (Gahnfelt et al., 2025; Hoppen et al., 2023; Hurley, 2018;
Sciarrino et al., 2020). Intensive trauma treatment is often performed by a
team of different therapists, rather than by a single therapist. This approach,
known as working with rotating therapists, means that patients have
therapy sessions with different professionals during their treatment. Such
treatment programs can consist of a single therapy such as EMDR therapy
(e.g., Hurley 2018), or a combination of various therapeutic components,
such as prolonged exposure, psychoeducation and physical and creative
activities (e.g., Voorendonk et al., 2023). Intensive trauma treatment
appears to be as effective as weekly trauma treatment (Hoppen et al.,
2023; Hurley, 2018) and may lead to faster symptom reduction (Gutner et
al., 2016). Consequently, intensive trauma treatment appears to result in
lower dropout rates than weekly trauma treatment (Gahnfelt et al., 2025).
For example, Van Woudenberg et al. (2018) reported a dropout rate of less
than three percent and Bongaerts et al. (2022) achieved no dropouts, which
is much lower than the dropout rates in weekly PTSD treatments, ranging
from 20% to over 30% (Imel et al., 2013; Niles et al., 2018).
For individuals with MID-BIF, intensive trauma treatment with rotating
therapists has also shown promising results, including for children and
adolescents (Ooms-Evers et al., 2021), families (Mevissen et al., 2020), and
adults with severe behavioural problems (Versluis et al., 2025a). Versluis
et al. (2025) investigated the efficacy of Intensive EMDR therapy delivered
twice a day, four days a week for two weeks by a team of six EMDR
therapists. PTSD symptoms were significantly reduced, with 9 out of 11
participants no longer meeting the diagnostic criteria post-treatment, and
one of twelve dropping out.
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Experiences with intensive trauma treatment
In a questionnaire study with participants in the general population, Van
Minnen et al. (2018) found that participants generally preferred treatment
from a rotating team of therapists rather than from an individual therapist.
A qualitative study by Thoresen et al. (2022) reported that participants
experienced daily sessions as very demanding but worth the effort in
terms of reducing symptoms. Therapists’ rotation was also highlighted as
important for treatment efficacy. Butler and Ramsey-Wade et al. (2024)
conducted in-depth interviews to explore the experiences of participants
undergoing Intensive EMDR therapy. EMDR therapy was perceived by their
participants as safe when carried out intensively, promoting the autonomy,
and involvement of the participants.
 Individuals with MID-BIF and rotating therapists
In psychotherapy and trauma treatment literature, on people in the
general population, therapeutic alliance is recognised as a key predictor of
treatment outcomes (Baier et al., 2020; Flückiger et al., 2018; Horvath et
al., 2011; Howard et al., 2022). These authors define therapeutic alliance
as a collaborative relationship between therapist and client, built on
agreement about treatment goals, consensus on therapeutic tasks, and the
development of a positive emotional bond, an understanding grounded in
Bordin’s pantheoretical model (Bordin, 1979, 1994).
Therapeutic alliance may be particularly important for individuals with
MID-BIF and severe behavioural problems. Cognitive deficits, limited social
and communicative skills, and attachment difficulties (Adams & Emerson,
2015; Hamadi et al., 2021; Van Herwaarden et al., 2022) may make it more
challenging to build trust, agree on goals, understand the tasks in the same
way, and experience a bond. Additionally, individuals with MID-BIF relatively
frequently experience interpersonal traumatic events, such as physical,
sexual, and emotional violence (Rittmansberger et al., 2020; Wigham &
Emerson, 2015), which may increase their need for safe and continuous
interpersonal relationships. Against this background, the use of rotating
therapists to deliver intensive trauma treatments may appear at odds with
what clients with MID-BIF may need. However, even if the trauma therapy
does not offer an opportunity for fulfilling interpersonal needs, for example
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because therapy is given by a team over a brief period, it may still be
possible to establish trust and agreement on goals and tasks (i.e., aspects
of therapeutic alliance) between client and team, if the team takes sufficient
time for this and adopts a supportive attitude (Schipper-Eindhoven et al.,
2024).
Current study
This study explored the experiences of adults with MID-BIF, PTSD, and
severe behavioural problems who participated in the study by Versluis et
al. (2025a), a brief Intensive EMDR therapy with rotating therapists. Three
participants were interviewed before and after the treatment to gain a
deeper understanding of their experiences. These perspectives were
further enriched and contextualised through interviews with professional
caregivers and therapists. Observations during the treatment process and
field notes were included to provide a more comprehensive view of the
therapeutic experience.
Methods
Study Design
This qualitative study employed an interpretative phenomenological
analysis (IPA) approach to explore the experiences of individuals with
MID-BIF, PTSD and severe behavioural problems who had participated in
a study on brief Intensive EMDR therapy with rotating therapists (Versluis
et al., 2025a). IPA focuses on understanding how individuals make sense
of their personal experiences within their specific context, offering insight
into the subjective narratives of participants through in-depth interviews
and detailed case-by-case analysis (Pietkiewicz & Smith, 2014; Smith &
Osborn, 2008). IPA is not about the generalisation of research findings but
focuses on the perceptions and understanding of a particular and often
homogeneous set of individuals. Although the number of participants varies
across the studies from single case studies to studies with more than 15
participants, Smith and Osborne (2008) state that a sample of three allows
for sufficient in-depth engagement with each individual case, but also allows
for a detailed examination of similarities and differences, convergence, and
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divergence, offering a nuanced understanding of how individuals make
sense of their lived experiences. In line with the idiographic nature of IPA,
thematic saturation was not pursued (Hale et al., 2007; van Manen et al.,
2016). Instead, we aimed for interpretive depth within individual cases,
using multiple data sources per participant.
Participants and setting
This study expands on the work of Versluis et al. (2025a), who examined
the efficacy of Intensive EMDR therapy with a team of rotating therapists
with individuals with MID-BIF, PTSD, and severe behavioural problems. To
recruit participants for the current study, the first three individuals who had
been included in the original study by Versluis et al. (2025a) were invited.
However, as one of them declined to participate, the fourth included
participant was invited and agreed to take part in this study. This resulted
in a final sample size of three, as originally intended. All the participants
received an information letter and provided written informed consent for
participation. The study protocol was approved by the Medical Research
Ethics Committee of the East Netherlands (reference number: 2020-6967-
NL75909.091.20). Participation in this study was voluntary. The three
participants were all men, aged between 20 and 30 years. Two of them
were classified with BIF and one with MID. All participants met the DSM-
5-TR diagnostic criteria for PTSD and had severe behavioural problems
(classified as Care Intensity Level [in Dutch: Zorg Zwaarte Pakket; ZZP] 7),
which represents eligibility for the highest level of care intensity according
to the Dutch healthcare authority, indicating the need for intensive support
due to severe behavioural problems as described in their client files).
All participants lived in supported housing on a care park in the Netherlands
(‘s Heeren Loo). The house accommodated six to eight other adults with MID
or BIF. Each participant had their own bedroom with an ensuite bathroom
and toilet and received 24-hour care from professional caregivers. One
participant worked four days a week, with professional caregivers providing
supervision and support. Another participant was fulfilling a community
service sentence (as mandated by the court because of an offence he had
committed) before starting the therapy. Despite various attempts to find
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suitable daytime activities or employment, this participant, along with the
third participant, was unsuccessful in securing such opportunities.
For each participant, a professional caregiver was involved in the study
and regularly supported them in their daily life. Additionally, three of the
six EMDR therapists involved in the therapy study (Versluis et al., 2025a)
participated in this study.
Brief Intensive EMDR therapy with rotating therapists
Participants received EMDR therapy twice daily for a maximum of two
weeks, provided by six different EMDR therapists. All were certified ‘EMDR
Europe practitioners’ or had completed the basic and advanced EMDR
courses accredited by the Dutch EMDR Association and had treated at
least 20 clients with MID-BIF for PTSD using EMDR therapy prior to the
start of the study. The participants received therapy in a room located in
a building on the care park where they lived. See Versluis et al. (2025a) for
a detailed description of therapy. A week before therapy, psychoeducation
about PTSD and EMDR therapy was provided to professional caregivers
and, if possible, the participants’ relative. It was agreed with the
participants’ team of professional caregivers that before and after therapy
sessions, participants would resume their usual daily activities, such as
going to work. In cases where existing programs did not provide sufficient
activities, a tailor-made plan was developed. These activities may include
craft or household chores. A professional caregiver, and the participant
determined whether a professional caregiver would be present during the
therapy sessions. Participants were not trained in coping skills or emotion
regulation techniques prior to the treatment (Josefa et al., 2019).
The first therapy session included making a case conceptualisation (a list of
traumatic and stressful events to be treated), and psychoeducation about
PTSD and EMDR therapy was provided to the participant. Each subsequent
therapy session consisted of 60 minutes of EMDR therapy, whereby the
EMDR protocol for children and adolescents up to 18 years of age (De Roos
et al., 2021) was used. Once a memory was successfully processed, it was
marked as complete on the participant’s case conceptualisation list. Therapy
then moved on to the next traumatic event. Therapy was completed after
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all memories of the case conceptualisation were processed. Treatment
duration varied depending on the number of traumatic and stressful events
and the time required to process these events.
Data collection
In-depth interviews were conducted to generate a description of the
participants’ expectations (before) and experiences (after) of receiving
Intensive EMDR therapy with a team of rotating therapists. A total of fifteen
interviews were conducted, and three participants and their professional
caregivers were interviewed two weeks before and two weeks after the
therapy, whereas the three therapists were only interviewed two weeks
after the therapy. The main topics of the interviews were: ‘Expectations/
experiences with EMDR therapy’, ‘Expectations/experiences of the intensive
of the therapy’, and ‘Expectations/experiences of therapy with six different
therapists.
The interviews were conducted individually with each participant,
professional caregiver, and EMDR therapist in their preferred setting (i.e.
participants’ homes, care facilities, or therapy room). The first author, who
conducted all the interviews, did not participate in the therapeutic process,
minimizing potential bias related to dual involvement. The interviews were
recorded and transcribed verbatim. Observational data and field notes
were recorded immediately after each interview, and field notes from the
intervention study (Versluis et al., 2025a) were examined.
Analysis
Data analysis was conducted according to the IPA guidelines (Smith &
Osborn, 2008). Four researchers (first, second, last author, and a master’s
student at Radboud University) collaborated in this process. A shared
analysis was central to ensuring the trustworthiness of the findings.
Researchers engaged in seven discussion meetings (see step three, four
and six below) to compare interpretations and reduce potential bias,
facilitating a more nuanced understanding of the data. For example,
during one meeting, a researcher suggested that a participant’s responses
appeared socially desirable because of the frequent repetition of the
interviewer’s words, while another researcher highlighted instances where
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the participant contradicted the interviewer, indicating that the responses
of the participant were not (all) socially desirable. These discussions helped
develop a more balanced and accurate interpretation of the data.
This analysis was guided by the steps outlined by Smith et al. (2022). In the
first step, the first author and the master student read the transcripts of the
participants, their professional caregivers, and the EMDR therapists several
times to develop a comprehensive understanding of the content and ensure
deep engagement with the participants’ experiences. In the second step, the
first author and the master’s student took detailed notes on each transcript,
focusing on key elements and emotions, while the second and last author
took more general notes. In step three, the first, second and last author and
the master student identified patterns based on the initial notes, while in the
fourth step the first, second, and last author and the master student met
twice to analyse the data of the first participant. In the first meeting, they
discussed the interviews with the first participant, while they focused on
the interviews with the professional caregiver and therapists in the second
meeting. After analysing the data of participant one, the four researchers
moved on to the fifth step, in which they repeated steps one, two, three and
four for participant two and three to ensure that each individual experience
was fully understood and that the analysis remained consistent across all
cases. Finally, in step six, after all cases had been analysed, the researchers
held a final meeting to identify overarching patterns across the participants.
General topics that captured common experiences and variations within
the dataset were developed.
Results
The results were structured around the three main topics discussed in the
interviews. In the first section, the individual expectations and experiences
of each participant regarding EMDR therapy are described. The second
section focusus on the participants' expectations and experiences
regarding the intensity of EMDR therapy. Finally, the third section explores
their expectations and experiences of receiving EMDR therapy from six
therapists.Expectations of and experiences with EMDR therapy
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Participant one
Participant one (before therapy): “I just need that therapy to
calm my mind but also to be able to trust people again. Because
it’s also very commercial you need to get food into the kiosk.
Well, you cannot just get it. You have to call abroad and do all
that. You have to trust people, you have to go there.”
Prior to therapy, participant one said he was motivated to engage in therapy.
His future dream is to start a skate park abroad, and in his private room, he
has built a model of it, complete with ramps, seating areas, and a small kiosk.
He said that EMDR therapy would help him to trust people again, which
he sees as essential for making his dream come true. At present, his lack
of trust prevents him from, for instance, calling people abroad to arrange
supplies for the kiosk in his envisioned skate park. This reflects a tension
between his wish to trust others and his fear of doing so, a dilemma that
could complicate trauma treatment when working with rotating therapists.
Participant one (before therapy): “I have had it [EMDR therapy]
before, but I could not... [I am afraid that] I might get angrier
afterwards... That I will withdraw a lot, I am afraid of that... That
is why I stopped before, and now I just want it to go well.”
Participant one had previously received EMDR therapy, but reported that
it was not successful at that time. The participant was unable to explain
why the therapy was ineffective. However, later in the interview, he
expressed concerns that he might become angry during EMDR therapy
and, consequently, display aggressive behaviour towards the therapist. He
was also worried that he might withdraw, isolate himself from his private
room, and stop attending therapy. Despite these concerns, participant one
was determined to fully engage in the therapy and hoped that it would be
effective this time.
5
Participant one (after therapy): “When I did it [EMDR therapy] the
first time, I started crying…. I just hate it. I just hate being angry.
I hate crying. I hate that feeling... And then I thought: I need to
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stop... Then I tried it [EMDR therapy] once more, and then I did
not do it anymore.”
Therapist three (after therapy): “He is too afraid of his reaction
when he gets therapy... That he has no control over it.”
During the first EMDR therapy session, participant one cried intensely while
thinking of a traumatic memory. He later reported feeling overwhelmed
by sadness and anger, finding it difficult to experience these emotions.
According to the therapist, he was particularly afraid of his own intense
reaction, which he felt unable to control. Participant one struggled to cope
with this and did everything he could to avoid feeling emotions. For example,
he avoided thinking about the traumatic memory during the session and was
unable to select the most distressing image from the traumatic memory.
Despite this, participant one continued to attend the therapy sessions.
During subsequent sessions, he exhibited seemingly threatening behaviour,
such as placing his feet on a table and saying that he could kick very hard
with them. Although he said he wanted to continue therapy, he repeatedly
left the sessions. Therapists interpreted his behaviour as a way of avoiding
confronting traumatic memories and accompanying emotions. Throughout
the sessions, the therapists attempted various strategies to break the
avoidance behaviour, including psychoeducation, offering a flashforward
(i.e. a technique in which the patient is confronted with a future situation
reflecting their anxiety about therapy) and applying EMDR 2.0, that is,
activation of the trauma memory combined with intensive distracting tasks
and enhancing motivation to counter avoidance (Matthijssen et al., 2021).
Despite these efforts, the therapy process could not be resumed, and the
therapy was terminated after six sessions, in joint decision with participant
one. His strong emotional reactions and withdrawal may reflect a lack of
perceived safety during therapy but seemed to be primarily driven by fear of
being overwhelmed by his own emotions in the first therapy session.
Participant two
Participant two (before therapy): “[Things that get better after
therapy] just in everyday life, like when you go to the shop,
especially in the evening... Sleeping better.”
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Professional caregiver two (before therapy): “I am actually really
glad he is going to do it [EMDR therapy], because I am especially
curious to see the young man he might become afterwards.”
Participant two had never received EMDR therapy before. He said he was
motivated to participate and hoped that the therapy would make everyday
activities, such as going to the shop, easier. However, he was unable to
explain what he precisely meant by this or why he expected this outcome. He
especially hoped that his sleep would improve, as he frequently experienced
nightmares and often lay awake at night. His professional caregiver said
that she was pleased he was starting the therapy. Although she could
not specify what she expected to change as a result of successful EMDR
therapy, she was curious about its potential effects on the participant.
Participant two (before therapy): “Not talking about it [traumatic
memories] is not an option anyway.”
Professional caregiver two (before therapy): “I expect that he
will just go through it [EMDR therapy] completely fine, because
it [EMDR therapy] is functional for him, but I think there is still a
chance that he might shut down.”
Although participant two could not clearly articulate what he expected from
the EMDR therapy, he was aware that discussing his traumatic memories
would be necessary during treatment. Professional caregiver two expected
him to participate well in therapy because it was important to him. However,
she also acknowledged the possibility that he would shut down and would
be unable to talk if he became overwhelmed.
5
Professional caregiver two (after therapy): “He broke down, he
was crying like a little child, just really crying. In the end, we
drove to the sheepfold. He cried the entire way in the car, but
nothing came out. Then we walked around a bit there, looked
at the sheep, and he started to calm down a bit. I did not talk
about it any further, and later on he brought it [traumatic event]
up again.”
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The start of EMDR therapy for participant two was difficult. He missed three
therapy sessions during the first three days of treatment. He remained in
bed despite his caregivers encouraging him to attend the therapy. When
he attended therapy, he exhibited dissociative behaviour; he sat silently in
his chair and stopped responding to the therapist, which meant that he
was unable to follow the therapy properly. The therapists decided to let
him walk around during the sessions so that the movement would prevent
him from lying down quietly and shutting himself off the therapy process.
His tension increased, and he ended the therapy session with a Subjective
Units of Disturbance (SUD) score of 10 (0 = no distress to 10 = extreme
distress). After this session, his professional caregiver decided to drive with
him to a sheepfold so that she could talk to him calmly. During the drive,
he began to talk spontaneously about his intrusive distressing memories.
This moment showed how emotional safety created outside the therapy
room, with a trusted caregiver, enabled him to open up, underlining the
importance of relational security in supporting affect regulation. On the
same day, therapists discussed that the traumatic memory they had been
treating up to that point might have been triggered by other traumatic
memories. They decided to treat these other traumatic memories first
using EMDR therapy. When the participant returned to therapy the next day,
the therapy progressed step-by-step. Ultimately, the original memory, which
had previously ended at a SUD of 10, was successfully treated to reach a
SUD of 0, meaning that the patient no longer experienced distress when
thinking of the traumatic memory.
Participant two (after therapy): “When they ask questions, I think
back and then you think back. And they [EMDR therapists] say;
then you think about it and there are all kinds of thoughts that
come to mind... And then you get distracted and they say; yes,
that image, yes no, that image is no longer there.”
Participant two (after therapy): “Then [in the second week] you
already know what to do because you know what’s going to
happen.”
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Participant two appears appeared to have experienced a learning effect.
As he became more familiar with the therapeutic approach, he found it
easier to follow instructions, which may have improved the effectiveness
of the therapy. During the Intensive EMDR therapy sessions, participant two
took notes on his phone about his progress. This seemed to have helped
him gain more control and provide a better overview. The learning effect
and support he gained from his notes appear to have contributed to the
success of the therapy.
Participant two (after therapy): “[Therapy helped] yes... Still,
because you never know if it [traumatic symptoms] will come
back.”
Professional caregiver two (after therapy): “He will be returning
to work soon, or at least to the farm two or three days a week...
I also think he is a little more open, including towards new
caregivers.”
Two weeks after EMDR therapy, participant two indicated that the therapy
had helped him. However, he was not yet convinced that the improvements
would be permanent and wanted to wait and see before he could be
definitively positive about the effect of therapy. His professional caregiver
noted that he was becoming more open, including new caregivers, and
slowly resumed his daily activities. For example, one week after the
interview, he would start working part-time on a farm. She considered this
a positive development, as he had no structured daily routines.
Participant three
Participant three (before therapy): “I don’t really know what to
expect from EMDR itself... That I have to follow a light with my
eyes, which moves very quickly. That I have to do it and that at
the same time I have to feel that I actually have to respond to it.
I suspect that’s how it will work.”
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Participant three already received EMDR therapy three times and, therefore,
had a fairly clear idea of how an EMDR therapy session would proceed. The
first two times, the therapy was successful. The last time he felt it did not
have the right effect, although he could not explain why it did not work at
that time. He hoped to use EMDR therapy to finally process his traumatic
memory.
Participant three (before therapy): “I expect EMDR to help me,
at least to the extent that I will be able to control my aggression
better... Because what often happens is that I physically attack
my professional caregiver, so I really squeeze or scratch or bite
or hit or kick... I am just still very afraid that if I continue with
that kind of behaviour, the home will no longer be my place...
I am afraid of closed institutions, such as crisis centers, partly
because my mother warned me about them.”
Participant three hoped that EMDR therapy would help him better control
his aggression. He was worried that if he did not become less aggressive, he
would be forced to leave the supported housing where he lived and would
be placed in a closed institution, such as a crisis centre. He hoped that
the therapy would help him change his behaviour, enabling him to continue
living in his current home.
Therapist three (after therapy): “If you look at participant three,
for example, who actually had a very nice process, who came
and noticed quite quickly that he already had marked traumatic
memories on his list [for successfully treated traumas]... So he
noticed quite quickly that he was making good progress through
the list... Yes, that is of course super motivating.’
Participant three (after therapy): “That I was yawning a lot
during the therapy treatment and every therapist told me: this is
because you are working on it, so it’s very normal, everyone has
that during EMDR therapy, they said.”
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Participant three attended every session and tried his best. Each time
a traumatic memory was treated, he marked it with a tick on the list of
traumatic memories to be treated. This symbolised the progress he made,
which motivated him to continue with the treatment. He sometimes felt
insecure when things occurred during therapy that he could not control, such
as laughing or yawning during the sessions. After the therapists explained
that reactions such as laughing or yawning were normal and part of the
process and that the therapy was going well, he decided to continue with
the therapy. Predictability and consistent reassurance across therapists
appeared to support his motivation and trust, as the therapists responded
in a similar manner to his reactions, which helped him feel understood and
safe despite the rotation of therapists.
Participant three (after therapy): “Unfortunately, I feel that I have
not quite achieved the goal [of becoming less angry] yet... I think
I get angry less often, but I also think I get less intense than
before... I am satisfied with that.”
Professional caregiver three (after therapy): “During those weeks
[in which EMDR therapy was administered], I did notice a certain
lightness... That he really did become happier and lighter there
[with EMDR therapy].”
After the first few sessions, participant three, as well as his professional
caregivers and parents, noticed positive changes. During the first week of
therapy, his caregiver contacted the therapists to report that Participant three
had become calmer and happier. Even after the therapy ended, participant
three remained positive about the results; he felt calmer, although he could
still get angry but less often and less intensely. However, he would have
preferred that ‘it would be completely over’ and that he would never get
angry again.
Expectations/experiences of the intensity of the EMDR therapy
Participant one (before therapy): “I have not thought about that
[the intensity of the therapy] yet, but now that I think about it, I
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find it very exciting ... I hope this [Intensive EMDR therapy] works,
because once a week did not help.”
Participant two (before therapy): “[The advantage of intensive
therapy is] that you remember things better... Because if you do
it in six months, you do not remember what you said six months
ago.”
Participant three (before therapy): “The intensive part does not
matter to me... No, I do not mind that it is a lot. Because I just
think it is important that it gets done... For me, it is all about the
EMDR.”
Although the participants were informed about the structure of the program
before EMDR therapy, they did not fully understand what the treatment
program would look like in practice. Nevertheless, they seemed generally
positive. Participant one indicated that the intensive approach was exciting
and hoped it to be more effective than the weekly sessions he previously
attended. Participant two considered the intensity as an advantage because
he believed that if sessions were too far apart, previously discussed
topics could be forgotten. His notes and learning experiences also helped
him to gain a better understanding of the process. Participant three had
no objections to the intensive approach and believed that the number of
sessions would not matter, as long as he could achieve his goal with the
therapy. For him, the most important thing was that the therapy would help
him processing his traumas, and he was convinced that the intensity would
help in this regard.
Participant one (after therapy): “That I got rid of it [EMDR therapy]
faster.”
Professional caregiver one (after therapy): “I was afraid that if
he had done it once a week, he would have dropped out more
easily, because he would have had so many days to think of all
kinds of reasons not to... I do not think that it [the intensity of
the EMDR therapy] was very negative. I think it [the intensity of
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EMDR therapy] has been very positive. He did not find it difficult
either.”
Participant two (after therapy): “I think if you have it [EMDR
therapy] every week for so many weeks, then I’m going to do
other things... If you only go once a week and you do not go for
two weeks... then I think in the third week: hey, they have not
said anything yet.”
Therapist two (after therapy): “I think if you have that [not coming
to EMDR therapy] a few times in a row and you see each other
weekly, the barrier to come back becomes quite high.”
After participant one had stopped therapy, he indicated that if he started
EMDR therapy again, he would prefer an intensive program to make faster
progress. His professional caregiver believed that an intensive program
was more suitable for participant one, as he might have dropped out even
sooner in a less intensive therapy format. Participant two shared a similar
view: he indicated that if the therapy had been less intensive, he would
quickly start doing other things and lose his motivation. He believed that
if there was too much time between sessions (e.g. two weeks), he would
already have doubts about the progress in the third week, which could
result in him ending the therapy prematurely. Both participants indicated
that they would have been more likely to stop if the therapy had been less
intensive, which emphasised their preference for more intensive EMDR
therapy. Therapist two confirmed this notion as she explained that when
there is more time between sessions, the barrier for returning to therapy
becomes considerably higher, which can lead to more dropouts. Participant
three did not express any specific opinions on this matter.
Expectations/experiences of EMDR therapy with six different therapists
Participant one (before therapy): “[Exciting], that I have to trust
those people.”
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Participant two (before therapy): “[Different therapists] I do not
really know what to think about that... I do not know how it will
be.”
Participant three (before therapy): “No, I do not mind... that six
therapists are involved.”
The three participants did not have clear expectations about working with
multiple therapists in advance, and the expectations differed from one
another. Participant one had reservations about receiving EMDR therapy
from different therapists because he found it difficult to trust people. For
example, when there was a new professional caregiver, he preferred to stay
in his private room, so he did not have to see the new professional caregiver.
Participant two said that he did not know what to expect from the therapy
and that he had no clear expectations of the different therapists either.
Participant three had no problems working with six different therapists.
Participant two (after therapy): “I do not know if I had all six
[therapists]. I thought there were three or so.”
Participant three (after therapy): “Well, I, um... I could handle it
[different therapists]... I actually liked it... I liked that they were
different.”
After completion of the therapy, participants two and three indicated that
they had no problems working with multiple therapists. Participant two
did not realise that he had seen six different therapists; he thought there
were only three. Participant three actually enjoyed receiving therapy from
different therapists.
Participant one (after therapy): “The other [therapist] didn’t
understand me and that made me angry, so I just told her to
go... Because she had known me longer [I preferred her]... She
already knew most things.”
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Professional caregiver one (after therapy): “He was just looking
for excuses not to go anymore, to escape, in my opinion.”
Therapist three (after therapy): “He did the same thing [being
angry] with my colleague therapist. He was so inappropriate and
angrily pissed, he did the same thing with me... He chose me
[as his preferred therapist], but he also walked out angry on me
once... [For the next therapy session], I would have two people
there. I would not do it all by myself.”
After completing therapy, participant one spoke negatively about one
therapist. According to the professional caregiver, the participant exhibited
challenging behaviour during the session with this therapist, such as
verbally threatening the therapist: “I can kick you with these feet.” However,
according to the therapist and professional caregiver, participant one also
exhibited this behaviour with other therapists, even with the therapist he
preferred most. Despite his preference for this therapist, the sessions,
even with her, were unsuccessful. According to the professional caregiver,
participant one was mainly looking for excuses to escape therapy. Based
on the interviews, it remained unclear whether the rotating therapists had
a negative impact on the therapy process of participant one. Nevertheless,
the therapists noted that if therapy with participant One were to continue, it
would be better for multiple therapists to be involved because they would
then be better able to provide him with EMDR therapy. This suggests that,
although the rotation of therapists may have contributed to participant
one’s discontinuation of therapy, the therapists recognised that they could
only continue delivering the therapy through shared responsibility, which
is particularly noteworthy given that these therapists all lacked prior
experience working as a team
5
Discussion
Participants started Intensive EMDR therapy with a team of rotating
therapists with high expectations. While expectations were not always
met, participants reported mainly positive experiences with the therapy’s
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intensity and the use of rotating therapists. Even the participant who
discontinued treatment held a favourable view of both, based on in-depth
interviews with him, his caregiver, and a therapist.
Intensity of the EMDR therapy
Findings support the notion that intensive trauma treatment not only seems
to be effective for adults with MID-BIF and severe behavioural problems
(Versluis et al., 2025a) but is also experienced positively by participants
themselves. Participants reported that two daily EMDR sessions helped
them stay committed and complete their treatment. This aligns with
findings about experiences of individuals in the general population, in which
intensive trauma treatment is associated with increased engagement
(Butler & Ramsey-Wade, 2024; Thoresen et al., 2022). Although one
participant dropped out, two stated that they would have been more likely
to discontinue therapy if it had been less intensive, which matches the
low dropout rates found in research on intensive trauma treatment in the
general population (Bongaerts et al., 2022; Van Woudenberg et al., 2018).
EMDR therapy with six different therapists
Two of the three participants were very positive about working with different
therapists, while one was less positive. These results align with those of
Van Minnen et al. (2018), who found a general preference for treatment by
a rotating team rather than by a single therapist in the general population.
Several elements presented in the current study may have contributed
to the participants’ positive experiences, despite the involvement of six
different therapists. All therapists were highly experienced in both EMDR
therapy and working with individuals with MID-BIF and appeared to share a
professional and supportive attitude, which has been identified as a relevant
adaptation in EMDR for individuals with MID-BIF (Schipper-Eindhoven
et al., 2024). In addition, the brief intensive EMDR therapy followed a
structured format, using the child and adolescent EMDR protocol (De Roos
et al., 2021), which is written in simplified language and explicitly states
that clients cannot make mistakes. The use of this protocol makes the
treatment transferable between therapists, and the format allowed for the
involvement of caregivers, which may have further supported participants,
as recommended for individuals with MID-BIF by Schipper-Eindhoven et
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al. (2024). These elements may have supported agreement on treatment
goals and tasks, aligning with key components of a therapeutic alliance
(Bordin, 1979, 1994), even though a positive emotional bond was likely not
established. In contrast, it remains unclear whether working with rotating
therapists influenced the third participant’s decision to stop therapy.
Involvement of the Support System
A component of Intensive EMDR treatment was the involvement of
participants’ professional caregivers and, if possible, a relative of the
participant. They received psychoeducation and were expected to ensure
that participants attended therapy sessions on time, provide emotional
support after difficult sessions, and help them resume their daily routines.
Nevertheless, participants’ support systems were only minimally involved
in the therapy process. Only one clear example was identified in which a
professional caregiver provided support by accompanying the participant
and being available to listen to him, and this seemed incidental rather than
structurally integrated into the treatment. Despite this limited involvement,
most participants still made progress. The extent to which a more active
and consistent involvement of the support system before, during, and after
therapy could have improved outcomes remains unclear.
Limitation and future research
IPA is not designed for generalisation (Pietkiewicz & Smith, 2014; Smith &
Osborn, 2008), and as common in these types of studies, there is a notable
homogeneity within the set of participants: all were males aged between 20
and 30, living in supported housing at a care park of a single ID care service
in the Netherlands, and all were treated by the same therapists at the
same time. It is important to acknowledge that the particular institutional
care environment, staff expertise, and cultural context of this setting likely
shaped participants’ experiences, which means these findings may not
fully translate to other care settings or populations. Future studies could
examine whether similar experiences and outcomes are observed in more
diverse populations, including different age groups, gender, living situations,
and care contexts.
5
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While researchers held multiple discussion meetings to compare
interpretations and reduce potential bias, and participants shared both
positive and negative experiences, it cannot be entirely ruled out that social
desirability may have influenced some responses during the interviews. All
therapists involved were highly experienced in both EMDR and working with
people with intellectual disabilities, and they received supervision multiple
times during the therapy process, which likely reduced differences in how
therapists conducted EMDR (e.g., timing of cognitive interweaves or dealing
with avoidance behaviour). This raises questions about the potential role of
therapists’ expertise in the acceptability and effectiveness of this treatment
format. Specifically, it would be valuable to explore whether participants’
positive experiences with different therapists are influenced by therapist
expertise and whether these experiences would remain consistent if the
treatment implementation became less uniform.
Finally, building on clients’ experiences, further research into the
organisational aspects of the therapy process is needed. One area worth
exploring is whether increased involvement of professional caregivers, for
instance, by accompanying clients after sessions to provide emotional
support, could enhance the therapeutic process.
Conclusion
Brief Intensive EMDR therapy with rotating therapists is not only effective
(Versluis et al., 2025a), but also well received by adults with MID-BIF and
severe behavioural problems, who generally express positive experiences
regarding both the intensity of the treatment and working with multiple
therapists
122]]></page><page Index="125" isMAC="true"><![CDATA[Experiences with intensive EMDR and rotating therapists
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General discussion]]></page><page Index="130" isMAC="true"><![CDATA[]]></page><page Index="131" isMAC="true"><![CDATA[General discussion
The studies presented in this dissertation aimed to improve the identification,
diagnostic assessment and treatment of post-traumatic stress disorder
(PTSD) in adults with mild intellectual disability (MID) or borderline
intellectual functioning (BIF). Adults with MID-BIF are at a higher risk of
developing PTSD than those in the general population (Mason-Roberts et
al., 2018; Mevissen et al., 2020a). However, PTSD is often not recognised
in these individuals (Mevissen et al., 2020a; Nieuwenhuis et al., 2019). This
may be partly explained by the limited availability of suitable diagnostic
instruments until recently (Hoogstad et al., 2025), which has complicated
the accurate identification and assessment of PTSD in these individuals.
Once diagnosed, it is important that individuals with MID-BIF receive PTSD
treatment, because untreated PTSD can have serious consequences
(Benedict et al., 2020; Davis et al., 2022; Gibson et al., 2020). Although
the number of treatment studies is growing in individuals with MID-BIF,
especially on eye movement desensitisation and reprocessing (EMDR)
therapy (for example, Byrne et al., 2022; Penninx et al., 2021; Verhagen et
al., 2023), there was still limited evidence at the start of our study regarding
the effectiveness of EMDR therapy in adults with MID-BIF and severe
behavioural problems. Behavioural problems could make EMDR therapy
more difficult to initiate or maintain, which underscores the importance
of examining whether EMDR therapy is feasible and potentially effective
in individuals with MID-BIF and behavioural problems. Research among
individuals in the general population shows that intensive trauma-focused
treatment is particularly effective, as it leads to a relatively fast reduction
in PTSD symptoms and low dropout rates (for example, Dell et al., 2023;
Gahnfelt et al., 2025; Hoppen et al., 2023; Oprel et al., 2021; Wachen
et al., 2019). Until recently, no studies had explored the effectiveness of
intensive treatment formats for adults with MID-BIF and severe behavioural
problems or how these individuals experience such intensive treatment.
To address the gaps in diagnostic assessment and treatment, this
dissertation had the following four objectives. First, to further examine the
psychometric properties of the adult version of the Diagnostic Interview
Trauma and Stressors – Intellectual Disability (DITS-ID-adults). Second, to
develop and evaluate a PTSD screener for adults with MID-BIF. Third, to
investigate the effectiveness of brief intensive EMDR therapy with rotating
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therapists for adults with MID-BIF and severe behavioural problems who
were classified with PTSD. Fourth, to explore the experiences of three
individuals with MID-BIF and severe behavioural problems who received
this treatment.
This chapter summarises the four studies included in this dissertation and
highlights two key findings: “PTSD can be recognised in adults with MID-
BIF through the Trauma Screener – Intellectual Disability (TS-ID)” and “Brief
intensive EMDR therapy with rotating therapists was effective in our group
of adults with MID-BIF, PTSD, and severe behavioural problems”, and ends
with the conclusion.
Summary of chapters
The first study, as described in Chapter 2, assessed the reliability and
construct validity of the DITS-ID-adults (Mevissen et al., 2018) in 97 adults
with MID-BIF living in supported housing. The interrater reliability of the
DITS-ID-adults proved good to excellent. The construct validity of the
DITS-ID-adults was good, based on positive correlations between the Brief
Symptom Inventory –18, revised Dutch version (BSI–18), Impact of Event
Scale-Intellectual Disability (IES-ID), Anxiety, Depression, and Mood Scale
(ADESS) and DITS-ID-adults, and mainly positive correlations between the
Behavior Problems Inventory (BPI) and DITS-ID-adults (r = .21 to r = .75).
Furthermore, it was found that reporting potentially traumatic events listed
under the DSM-5-TR A criterion for PTSD was associated with fulfilling
PTSD symptom criteria. A large proportion of participants met PTSD criteria
(58%), while only 7% had a documented PTSD diagnosis in their clinical file
prior to participation in the study. These findings highlight the urgent need
to improve PTSD recognition in individuals with MID-BIF.
The second study, detailed in Chapter 3, evaluated the adult self-report
and proxy versions of the Trauma Screener–Intellectual Disability (TS-ID),
which were adapted from the Dutch Child and Adolescent Trauma Screener
(Dutch abbreviation KJTS; Kooij et al., 2025; CATS-2; Sachser et al., 2022),
for use in adults with MID-BIF. The adult self-report version showed high
internal consistency (Cronbach’s α = .94) and excellent validity (AUC =
.94) in distinguishing PTSD in adults with MID-BIF. Optimal specificity
130]]></page><page Index="133" isMAC="true"><![CDATA[General discussion
and sensitivity were determined at a cut-off score of 18. Although the
proxy version of the TS-ID demonstrated excellent internal consistency
(Cronbach’s α = .93), it did not statistically distinguish PTSD in adults with
MID-BIF. These findings underline the potential of the TS-ID self-report
version as a reliable screening instrument for identifying PTSD in adults
with MID-BIF while also highlighting the limitations of the TS-ID proxy-report
version when used in these individuals.
The third study, presented in Chapter 4, examined the safety and
effectiveness of brief intensive EMDR therapy delivered by a team of
rotating therapists for 11 adults with MID-BIF, PTSD and severe behavioural
problems. The findings showed significant decreases in PTSD symptoms,
with nine out of eleven participants no longer meeting the PTSD diagnostic
criteria immediately after treatment and at the 9-week follow-up. Although
some participants showed small to medium improvements in adaptive
behaviour and behavioural problems, these changes were not consistent
across participants and therefore did not indicate an overall pattern of
improvement for the participant group. The latter conclusion also applies
to the use of involuntary care measures. Only one participant dropped out
of the therapy and declined to complete further questionnaires for Study 3
(Chapter 4). The intervention showed no adverse events, underscoring its
safety. These results suggest that brief intensive EMDR therapy with a team
of rotating therapists is a safe and effective treatment option for reducing
PTSD symptoms in adults with MID-BIF and severe behavioural problems.
The fourth study, as described in Chapter 5, qualitatively explored the
experiences of three adults with MID-BIF, PTSD and severe behavioural
problems who received brief intensive EMDR therapy with rotating
therapists. Interpretative phenomenological analysis revealed that
the participants started intensive EMDR therapy while holding high
expectations of the extent to which the treatment might change their lives.
One participant discontinued therapy early, and two completed the therapy.
All participants reported positive experiences with intensive therapy, and
two expressed positive experiences with the therapists’ rotation format.
Intensity was perceived to support continuity and engagement, particularly
when compared with weekly therapy sessions. Minimal involvement of
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the participants’ (professional) support systems was observed, with only
incidental support from caregivers rather than structured integration in the
treatment.
Key findings
This section presents two key findings derived from the four studies
presented in this dissertation. These findings bring together the results
across studies and conclude by reflecting on their implications for clinical
assessment, treatment, and future research.
Key finding 1: PTSD can be recognised in adults with MID-BIF through the
Trauma Screener – Intellectual Disability (TS-ID)
In Study 1 (Chapter 2), adults with MID-BIF, living in supported housing and
receiving 24-hour care from ID care services, were studied. Among the 97
participants, 58% could be classified as having PTSD according to the DITS-
ID, whereas only 7% had received a PTSD diagnosis prior to participation.
This discrepancy aligns with findings from other studies and illustrates
how PTSD often remains undetected in these individuals. Mevissen et al.
(2020a) examined 106 adults with MID-BIF who were receiving care from
ID care services and found a PTSD prevalence of 38% based on the DITS-
ID-adults, while only 6% had a PTSD diagnosis recorded in their client
file. Nieuwenhuis et al. (2019) conducted a study in 570 individuals with
severe mental illness in a tertiary mental health care setting and reported
a suspected PTSD rate of 48% among those with suspected MID-BIF,
based on an older screening instrument for PTSD. Nevertheless, PTSD was
recorded in only 2% of the client files. Together with our own findings, we
may conclude that although PTSD is relatively common in adults with MID-
BIF in clinical settings, it is not frequently recognised in clinical practice.
These findings highlighted the urgent need to improve PTSD recognition in
individuals with MID-BIF, because it is likely that if PTSD is not recognised,
effective trauma treatment will not be provided.
As described in the General Introduction (Chapter 1), professional caregivers
and clinicians face several challenges in recognising PTSD in individuals
with MID-BIF, and several explanations have been proposed for this. One
explanation is that professional caregivers are frequently unaware of the
132]]></page><page Index="135" isMAC="true"><![CDATA[General discussion
traumatic events that individuals with ID have been exposed to, which
hinders the identification of PTSD in this group (Hoogstad et al., 2024).
Another explanation why PTSD is often not recognised in adults with MID-BIF
may lie in the fact that when individuals with MID-BIF also have behavioural
problems (e.g., irritability, lethargy, stereotyped behaviour, aggression
towards others, or self-injurious behaviour), professional caregivers may
focus primarily on managing and regulating behavioural problems, which
can distract their attention from recognising possible PTSD symptoms
(McNally et al., 2021). This is particularly problematic given that PTSD and
behavioural problems are associated in people with MID-BIF, as observed
in Study 1 (Chapter 2) and as reported in other research (Mason-Roberts et
al., 2018; McNally et al., 2021; Rittmansberger et al., 2020).
The masking of PTSD symptoms by behavioural problems closely
resembles the phenomenon of diagnostic overshadowing, in which PTSD
symptoms are misattributed to the characteristics of ID or to symptoms
of other mental health disorders that are already diagnosed (Jopp & Keys,
2001; Wilsocki & Zalta, 2024). This phenomenon forms a third explanation
for why PTSD symptoms are often not recognised in adults with MID-BIF in
clinical settings. As a result of diagnostic overshadowing, PTSD symptoms
may be inaccurately attributed to symptoms of other mental health
conditions, such as autism, mood disorder, attention deficit hyperactivity
disorder (ADHD), or the ID itself. A notable proportion; that is, 30 out of 97
(31%) participants in Studies 1 and 2 (Chapters 2 and 3), had at least one
additional DSM-5 diagnosis (other than MID, BIF, or PTSD) recorded in their
client file, including autism spectrum disorder (21%), mood disorder (4%),
anxiety disorder (2%), personality disorder (3%), and ADHD (11%). This likely
increased the risk of diagnostic overshadowing in this group.
A contributing factor for not recognising PTSD in individuals with MID-BIF
is that the current PTSD guidelines do not sufficiently address individuals
with MID-BIF. While the multidisciplinary PTSD guidelines (Federatie
Medisch Specialisten, 2025) only briefly mention individuals with (M)ID,
they do not mention those with BIF. These guidelines do not include any
recommendations for screening, as the guidelines are aimed for the situation
when PTSD is already suspected. However, as demonstrated in Studies 1
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and 2 and in research by Mevissen et al. (2020a) and Nieuwenhuis et al.
(2019), PTSD is often not suspected in adults with MID-BIF. Although the
guidelines note that both the assessment and treatment of individuals with
(M)ID may require adaptations, it is not specified what these adaptations
should involve. Overall, the characteristics and needs of people with MID-
BIF are insufficiently addressed in the guidelines, which may contribute to
PTSD not being recognised and adequately treated within this population.
A final important factor for not recognising PTSD in adults with MID-BIF
is the limited availability of suitable diagnostic instruments until recently
(also see Hoogstad et al., 2025), which has complicated the accurate
identification and assessment of PTSD in adults with MID-BIF. The DITS-
ID, which was introduced in 2018, represented a first step for improving
the recognition of PTSD in adults with MID-BIF. In Study 1 (Chapter 2), we
examined the psychometric characteristics of the DITS-ID and found that
it was a reliable and valid instrument for classifying PTSD in adults with
MID-BIF, consistent with research conducted by Mevissen et al. (2020a).
However, the DITS-ID is not suitable for initial PTSD screening. At the start
of this research project, no screening instrument was available that had
been developed specifically for adults with MID-BIF and that aligned with the
DSM-5-TR criteria for PTSD. The lack of such a screener likely contributed to
not recognising PTSD in this group. As described in the General Introduction
(Chapter 1), it is essential that a PTSD screener for adults with MID-BIF is
both aligned with the current DSM-5-TR criteria for PTSD and adapted and
validated for adults with MID-BIF.
In Study 2 (Chapter 3), we evaluated the adult self-report and proxy
versions of the Trauma Screener–Intellectual Disability (TS-ID), which were
adapted from the Dutch Child and Adolescent Trauma Screener (Dutch
abbreviation KJTS; Kooij et al., 2025; CATS-2; Sachser et al., 2022), for use
in adults with MID-BIF. The self-report version of the TS-ID demonstrated
high internal consistency and excellent validity in distinguishing PTSD in
adults with MID-BIF. In contrast, while the proxy version also demonstrated
high internal consistency, it did not show validity in distinguishing PTSD.
This finding partly contrasts with research on the original KJTS (Kooij et
al., 2025), on which the TS-ID was based. In that study, the proxy version
134]]></page><page Index="137" isMAC="true"><![CDATA[General discussion
was primarily completed by parents (86%), which likely contributed to the
better recognition of PTSD symptoms by proxy. Parents are usually closely
involved in their children’s daily lives, unlike many professional caregivers,
who often have limited insight into their clients’ trauma history (Hoogstad
et al., 2024). The findings from Study 2 indicate that the TS-ID self-report
version is a psychometrically reliable and valid instrument for screening for
PTSD in adults with MID-BIF. This enables the identification of PTSD cases
that might otherwise have gone unnoticed in adults with MID-BIF. The TS-ID
self-report version represents a crucial step in recognising PTSD in adults
with MID-BIF, facilitating earlier identification and better access to trauma
treatment.
When interpreting this key finding, several limitations should be taken into
account. First, according to the DSM-5-TR, determining whether an individual
meets criteria for ID should not rely solely on IQ scores. Assessment of
adaptive functioning is equally important in determining whether an
individual meets diagnostic criteria for ID. In clinical practice and research,
the term BIF is often used for individuals with IQ scores roughly between 70
and 85, although BIF is not defined as a formal diagnostic category in the
DSM-5-TR and guidance on its specific characteristics and assessment is
limited. In Study 1 and 2 (Chapter 3 and 4), all participants had previously
been identified as having MID or BIF in their client file. However, in many
cases, this was primarily based on IQ scores, with limited information
available on adaptive functioning. As a result, it cannot be established with
certainty whether all participants would meet the current DSM-5-TR criteria
for MID, or whether they would fall within the commonly used range of BIF
based on a comprehensive assessment of adaptive functioning. Second,
we investigated a specific sample of adults with MID-BIF in Study 1 and 2
(Chapter 3 and 4), all living in supported housing of ID care services in the
Netherlands, which may limit the generalisability of the findings.
This key finding has several implications for clinical practice. First, the TS-ID
can be used not only when PTSD is suspected in adults with MID-BIF, but
also if they present with behavioural or psychological problems. As described
above, PTSD symptoms in this group are often masked by behavioural
problems or overshadowed by other mental disorders or characteristics of
6
135]]></page><page Index="138" isMAC="true"><![CDATA[Chapter 6
ID (Jopp & Keys, 2001; McNally et al., 2021; Wilsocki & Zalta, 2024), which
often lead to PTSD not being recognized in adults with MID-BIF. The TS-
ID may therefore help to clarify whether trauma-related symptoms may
underlie these behavioural or psychological problems. Second, the TS-ID
can be used after an individual has experienced a potentially traumatic event
to actively monitor whether PTSD symptoms develop. Recently, a study in
individuals with MID-BIF has shown that also stressful life events can result
in PTSD symptoms (Rouleaux et al., 2025). Therefore, the TS-ID may also be
considered following such events. Finally, given that the TS-ID and the DITS-
ID are currently the only measuring instruments specifically developed for
screening and classifying PTSD in adults with MID-BIF, it would be advisable
to consider including these instruments when de current PTSD guidelines are
updated. At present, the available guidelines do not include any assessment
tool suitable for this population, and acknowledging these tools help
professionals to better recognise and assess PTSD in adults with MID-BIF.
Building on this key finding, several suggestions can be given for future
research. Like adults with MID-BIF, children with MID-BIF also have an
increased risk of experiencing adverse life events compared with children
without MID-BIF (e.g., Dion et al., 2018; McDonnell et al., 2019; Mevissen
et al., 2016; Vervoort-Schel et al., 2021). However, no validated screening
instrument for PTSD according to the DSM-5-TR is currently available for
children with MID-BIF. Future research should adapt and evaluate trauma
screeners for this group so that PTSD can be better recognised in children
with MID-BIF. A second suggestion concerns examining whether the TS-
ID is also suitable for use in research and clinical practice to evaluate the
effectiveness of trauma-focused treatment. In Study 1 (Chapter 2), the
reliability and validity of the TS-ID were established, but its sensitivity,
that is its ability to detect meaningful change over time, has not yet been
investigated. Because the TS-ID can be completed in a relatively short time
(10 minutes) and uses a four-point response scale, it may be a practical
instrument for monitoring change during or after trauma treatment. In
Study 3 (Chapter 4) and several other ongoing intervention studies, the TS-
ID is already being used for this purpose. However, systematic research
into its sensitivity is needed to determine whether the TS-ID can reliably
capture treatment-related changes in adults with MID-BIF.
136]]></page><page Index="139" isMAC="true"><![CDATA[General discussion
Key finding 2: Brief intensive EMDR therapy with rotating therapists was
effective in our group of adults with MID-BIF, PTSD and severe behavioural
problems
In Study 3 (Chapter 4), twelve participants started brief intensive EMDR
therapy with rotating therapists, of whom eleven completed the treatment.
Those who completed treatment showed a significant reduction in PTSD
symptoms and nine of them no longer met diagnostic criteria for PTSD
immediately after treatment and at nine-week follow-up. No adverse events
were reported, supporting the notion that brief intensive EMDR therapy for
these individuals is safe. These findings align with those of other studies
on intensive trauma-focused treatments in children and adolescents with
MID-BIF (Ooms-Evers et al., 2021) and in families with MID-BIF (Mevissen
et al., 2020b).
The low dropout rate observed in Study 3 (Chapter 4) is consistent with
other research indicating that intensive trauma-focused treatments are
associated with lower dropout rates than weekly trauma treatments (e.g.,
Gahnfelt et al., 2025; Hoppen et al., 2023). In the two studies that examined
intensive trauma focused-treatment in individuals with MID-BIF, no
participants discontinued treatment (Mevissen et al., 2020b; Ooms-Evers et
al., 2021). A reason for the lower dropout rates in intensive trauma-focused
treatments lies in their structure, which is established by condensing
sessions into a short timeframe, minimising avoidance between sessions,
maintaining therapeutic engagement, and allowing PTSD symptoms to
decrease relatively quickly (Bongaerts et al., 2022; Thoresen et al., 2022;
Van Woudenberg et al., 2018). Study 4 (Chapter 5), which explored three
participants’ experiences with brief intensive EMDR therapy, offered some
support for this. Participants generally experienced the intensive format as
positive and helpful for maintaining engagement and completing treatment.
They described the high intensity as motivating and as contributing to a
sense of focus and continuity. Even the participant who discontinued
treatment early indicated that, if he were to receive EMDR therapy again, he
would once again prefer an intensive format, believing this would allow him
to make faster progress. His professional caregiver likewise believed that
an intensive format suited him well, noting that he might have dropped out
even sooner in a less intensive (weekly) format.
6
137]]></page><page Index="140" isMAC="true"><![CDATA[Chapter 6
In the study on brief intensive EMDR therapy, participants received treatment
from a team of six therapists who worked collaboratively and alternated
sessions, a format which is known as rotating therapists. In Study 4
(Chapter 5), we examined how participants experienced this format. Two of
the three participants were positive about working with different therapists,
while one was neither positive nor negative. These findings are consistent
with those from a study in individuals from the general population by Van
Minnen et al. (2018), who found a general preference for treatment by a
rotating team of therapists rather than by a single therapist. Although two
out of three participants were positive about the rotating therapists format,
this finding may seem somewhat at odds with the concept of therapeutic
alliance. As described in the General Introduction (Chapter 1), research in
psychotherapy and trauma treatment among the general population shows
that therapeutic alliance is a key predictor of treatment outcomes (Baier et
al., 2020; Flückiger et al., 2018; Horvath et al., 2011; Howard et al., 2022).
Therapeutic alliance refers to a collaborative relationship between therapist
and client, grounded in agreement about goals, consensus on tasks,
and the development of a positive emotional bond (Bordin, 1979, 1994).
Therapeutic alliance may be particularly important for individuals with MID-
BIF and severe behavioural problems, as skills deficits and attachment
difficulties can make it more challenging to build trust and agree on goals
and tasks (Hamadi et al., 2021; Van Herwaarden et al., 2022).
Against this background, the use of rotating therapists may thus appear
at odds. As said, two of the three participants were positive about working
with different therapists, while one was neither positive nor negative. Several
factors may have contributed to the positive experiences. All therapists
were highly experienced in both EMDR therapy and working with individuals
with MID-BIF and appeared to share a professional and supportive
attitude, which was identified as a relevant adaptation in EMDR therapy for
individuals with MID-BIF (Schipper-Eindhoven et al., 2024). Moreover, the
brief intensive EMDR therapy followed a structured format using the child
and adolescent EMDR protocol (De Roos et al., 2021), which is written in
simplified language and explicitly states that clients cannot make mistakes.
In addition, a case conceptualisation was developed together with the client,
based on a list of traumatic and stressful events ordered by SUD score.
138]]></page><page Index="141" isMAC="true"><![CDATA[General discussion
After each session, processed memories were checked off with the client,
providing continuous insight into the progress of treatment and supporting
a sense of safety, predictability, and involvement for individuals with MID-
BIF. The EMDR therapy protocol and case conceptualisation made the
treatment easily transferable between therapists. These elements likely
facilitated agreement between client and therapist on treatment goals
and tasks, aligning with key components of the therapeutic alliance, even
though a strong emotional bond might not have been established.
Study 3 (Chapter 4) examined the effectiveness of brief intensive EMDR
therapy in reducing PTSD symptoms and diagnostic status. In addition,
changes in adaptive behaviour, behavioural problems, and the use of
involuntary care were assessed as secondary outcomes. These outcomes
were included to explore whether successful reduction in PTSD symptoms
would translate into improvements in functioning in other areas. In Study
3 (Chapter 4), we hypothesised that if PTSD symptoms were effectively
reduced, behavioural problems would decline, adaptive behaviour would
improve, and the use of involuntary care would decrease. For adaptive
behaviour, an individual goal was formulated for each participant, such
as ‘participant independently walks home from work’. Some participants
showed small improvements in adaptive behaviour after brief intensive
EMDR therapy, whereas others exhibited medium changes. Improvements
were not systematic across participants, suggesting that improvements
in adaptive behaviour do not automatically occur following an overall
reduction in PTSD symptoms after trauma treatment.
Changes in adaptive behaviour may require interventions aimed at learning
new skills and adapting the environment. Although a reduction in PTSD
symptoms may enable a participant to walk home from work independently
because avoidance symptoms have decreased, the continued involvement
of professional caregivers, for example, accompanying the participant out
of habit or caution, may have inadvertently prevented actual improvements
in this adaptive skill. Although participants were supported by their regular
caregivers between therapy sessions, the qualitative study in Study 4
(Chapter 5), which involved three participants from Study 3, indicated
that caregiver involvement in the therapeutic process itself was limited.
6
139]]></page><page Index="142" isMAC="true"><![CDATA[Chapter 6
Previous research indicates that consistent caregiver involvement is
often essential for supporting the generalisation of therapeutic gains into
everyday functioning (Farnsworth & Schröder, 2025). Limited engagement
of caregivers in Study 3 (Chapter 4) may have reduced opportunities to
translate therapeutic gains into observable improvements in adaptive
behaviour in the clients’ natural environment.
After brief intensive EMDR therapy, some participants showed small to
moderate improvement in behavioural problems. However, when looking
across all participants, no consistent pattern of decrease in behavioural
problems emerged. The use of involuntary care measures also remained
unchanged, which may be related to the fact that such measures are
typically applied in response to severe behavioural problems (Hastings
et al., 2013). Study 1 (Chapter 2) and other research (Mason-Roberts
et al., 2018; McNally et al., 2021; Rittmansberger et al., 2020) show that
PTSD and behavioural problems are associated in individuals with MID-
BIF. However, relatively little is known about how these constructs are
related and whether improvements in PTSD symptoms lead to changes in
behavioural problems. Behavioural problems in individuals with MID-BIF are
understood to be multifactorial, meaning that they arise from the interaction
of individual, environmental and neurodevelopmental factors rather than
from one of these factors alone. These factors include limited adaptive
and communicative skills, exposure to stressful or chaotic environments,
psychiatric comorbidity, and biological or neurological vulnerabilities (van
den Akker et al., 2021). Although PTSD and behavioural problems co-occur,
these broader influences mean that improvements in PTSD symptoms
alone cannot be expected to produce a uniform decrease in behavioural
problems across individuals with MID-BIF and behavioural problems. That
behavioral problems are multifactorially determined may help explain
why some participants showed small to moderate improvements, and no
consistent pattern of decrease in behavioural problems emerged across
participants in Study 3 (Chapter 4).
When interpreting the second key finding, several limitations should be
considered. First, although the randomised non-concurrent multiple
baseline design used in Study 3 (Chapter 4) provides valuable insights
140]]></page><page Index="143" isMAC="true"><![CDATA[General discussion
into individual change in PTSD symptoms, it does not indicate which
subgroups, for example those differing in the type and number of traumatic
memories, within the MID-BIF population may benefit more or less from
intensive EMDR therapy. In addition, both Study 3 and Study 4 (Chapter
4 and 5) involved adults with MID-BIF living in supported housing within
one Dutch ID care organisation, and the participants in Study 4 formed a
small and selective group of young adult males treated within the same
institutional context. These factors limit the generalisability of the findings
to other settings or individuals.
This key finding supports offering EMDR therapy in an intensive format
for treating PTSD in adults with MID-BIF and severe behavioural problems.
An intensive approach may enhance treatment adherence and maintain
motivation. The positive experiences with multiple therapists further suggest
that working with a rotating team of therapists is feasible for individuals with
MID-BIF and behavioural problems. As this is, to our knowledge, the first
study to examine intensive EMDR therapy in adults with MID-BIF, further
research is required to replicate and extend these findings. Future research
should include more diverse groups, such as individuals from different types
of care settings, to examine the generalisability of brief intensive EMDR
therapy for individuals with MID-BIF. Furthermore, a randomised controlled
trial (RCT) comparing weekly EMDR therapy with intensive EMDR therapy
could provide valuable insight into the relative benefits of both treatment
formats and allow for the identification of potential moderators, such as the
number and type of traumatic events, living environment, or the presence of
severe behavioural problems, that may influence treatment responsiveness,
while also improving external validity. The absence of improvements in
adaptive functioning despite a reduction in PTSD symptoms highlights the
need for research examining the factors that determine whether treatment
effects translate into changes in everyday functioning. More research is
needed to identify which forms of caregiver involvement, environmental
adjustments, or additional interventions could support the generalisation
of treatment effects and facilitate improvements in adaptive behaviour
following trauma-focused treatment.
6
141]]></page><page Index="144" isMAC="true"><![CDATA[Chapter 6
Conclusion
This dissertation aimed to improve the identification, diagnostic assessment,
and treatment of PTSD in adults with MID-BIF. The case of Hilda, introduced
in the General introduction (Chapter 1), illustrated how PTSD can remain
unnoticed and how weekly trauma-focused treatment may be difficult to
sustain for individuals with MID-BIF. Taken together, the studies in this
dissertation show that several of these barriers can be addressed. The
findings indicate that PTSD can be recognised more systematically in
adults with MID-BIF by using instruments that are adapted and validated
for these individuals, such as the DITS-ID and the TS-ID. In addition, brief
intensive EMDR therapy with rotating therapists was effective in reducing
PTSD symptoms in our group of adults with MID-BIF, PTSD, and severe
behavioural problems. However, consistent with the pattern observed in
Study 3, these treatment effects were largely confined to PTSD symptoms
and did not consistently extend to improvements in behavioural problems
or adaptive functioning. For individuals like Hilda, this combination of earlier
screening, structured diagnostic assessment, and accessible intensive
trauma-focused treatment may offer a more timely, tailored, and realistic
pathway to care than is currently the case.
142]]></page><page Index="145" isMAC="true"><![CDATA[General discussion
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6
145]]></page><page Index="148" isMAC="true"><![CDATA[]]></page><page Index="149" isMAC="true"><![CDATA[Appendices]]></page><page Index="150" isMAC="true"><![CDATA[]]></page><page Index="151" isMAC="true"><![CDATA[Nederlandse samenvatting
(Dutch summary)]]></page><page Index="152" isMAC="true"><![CDATA[]]></page><page Index="153" isMAC="true"><![CDATA[Nederlandse samenvatting
Hoofdstuk 1 schetst de context van dit proefschrift. Aan de hand van de
casus van Hilda - een vrouw met een licht verstandelijke beperking - wordt
duidelijk hoe PTSS jarenlang onopgemerkt kan blijven. Hilda is als twaalfjarig
meisje uit huis geplaatst en woont inmiddels, als 32-jarige, alweer enige tijd in
haar huidige woonlocatie met 24-uurszorg. Wanneer Hilda plotseling ander
gedrag laat zien, vergelijkbaar met de verandering die op haar twaalfde in
het dossier staat beschreven, besluiten haar begeleiders een diagnostisch
interview naar trauma- en stressorgerelateerde stoornissen (de DITS-LVB)
af te nemen. Tijdens dit interview vertelt Hilda dat zij herhaaldelijk seksueel
is misbruikt. Op basis van het diagnostisch onderzoek wordt de classificatie
PTSS gesteld.
Om de context van dit proefschrift te begrijpen, is het belangrijk kort stil
te staan bij wat post-traumatische stressstoornis (PTSS) is en wie we
bedoelen met mensen met een LVB. Volgens de DSM-5-TR is PTSS een
psychische stoornis die ontstaat na blootstelling aan een potentieel
traumatische gebeurtenis (criterium A). Een gebeurtenis wordt als
potentieel traumatisch beschouwd als sprake is van feitelijke of dreigende
dood, ernstige verwonding of seksueel geweld. Iemand maakt dit zelf
mee, is er getuige van, hoort dat het een naaste is overkomen of is
herhaaldelijk blootgesteld aan aversieve details ervan. PTSS gaat gepaard
met een reeks symptomen, waaronder intrusieve symptomen (cluster B),
vermijdingssymptomen (cluster C), negatieve veranderingen in cognities en
stemming (cluster D) en veranderingen in arousal en reactiviteit (cluster
E). Deze symptomen veroorzaken significante lijdensdruk of beperkingen
in het functioneren, houden langer dan één maand aan en zijn niet het
gevolg van middelengebruik, een somatische aandoening of een andere
psychische stoornis.
Een verstandelijke beperking wordt volgens de DSM-5-TR gekenmerkt door
beperkingen in het verstandelijke en adaptief functioneren, die tot uiting
komen in de sociale, praktische en conceptuele domeinen en beginnen
tijdens de ontwikkelingsperiode. In zowel de klinische praktijk als in
wetenschappelijk onderzoek worden IQ-grenzen van 50 tot 70 gebruikt om
een licht verstandelijke beperking af te bakenen. Voor zwakbegaafdheid
worden doorgaans IQ-scores tussen 70 en 85 aangehouden. Hoewel
S
151]]></page><page Index="154" isMAC="true"><![CDATA[Appendices
zwakbegaafdheid in de DSM-5-TR niet onder een verstandelijke beperking
valt maar is opgenomen als een V-code, is het in Nederland gebruikelijk
om mensen met een licht verstandelijke beperking en mensen met
zwakbegaafdheid samen te brengen onder de noemer ‘LVB’.
Volwassenen met een LVB worden vaker blootgesteld aan potentieel
traumatische gebeurtenissen dan mensen uit de algemene bevolking.
Zij hebben bovendien minder cognitieve, communicatieve en sociale
vaardigheden om de gevolgen van dergelijke gebeurtenissen op een
natuurlijke manier te verwerken. Dat vergroot het risico op het ontwikkelen
van PTSS. Ondanks het verhoogde risico wordt PTSS bij volwassenen
met een LVB vaak niet herkend. Dit is problematisch omdat PTSS een
grote negatieve invloed heeft op het dagelijks functioneren. Binnen de
groep volwassenen met een LVB is EMDR-therapie momenteel de meest
onderzochte behandeling voor PTSS. Het aantal studies blijft echter
beperkt, vooral bij volwassenen met een LVB en ernstige gedragsproblemen.
Hierdoor bestaat in de praktijk onzekerheid over de veiligheid, effectiviteit
en haalbaarheid van behandeling met EMDR-therapie bij deze doelgroep.
Dit proefschrift bestaat uit vier studies die samen bijdragen aan het
verbeteren van de herkenning, diagnostiek en behandeling van PTSS bij
volwassenen met een LVB. Het eerste doel was het verder onderzoeken
van de psychometrische eigenschappen van het Diagnostisch Interview
Trauma en Stressoren – LVB voor volwassenen (DITS-LVB; hoofdstuk 2).
Het tweede doel was het ontwikkelen en evalueren van een screener voor
PTSS bij volwassenen met een LVB (hoofdstuk 3). Het derde doel betrof
het onderzoeken van de effectiviteit van kortdurende intensieve EMDR-
therapie bij volwassenen met een LVB, PTSS en ernstige gedragsproblemen
(hoofdstuk 4). Het vierde doel was het verkennen van de ervaringen van
drie volwassenen met een LVB die deze behandeling hebben ontvangen
(hoofdstuk 5).
Hoofdstuk 2 beschrijft een onderzoek naar de psychometrische kenmerken
van de DITS-LVB (versie voor volwassenen). De DITS-LVB is ontwikkeld om
PTSS bij volwassenen met een LVB te classificeren. In deze studie werd het
interview afgenomen bij 97 volwassenen met een LVB. Ter beoordeling van
152]]></page><page Index="155" isMAC="true"><![CDATA[Nederlandse samenvatting
de constructvaliditeit vulden deelnemers de Nederlandse versies van de
Brief Symptom Inventory-18 (BSI-18; angst-, depressie- en stressklachten)
en de Impact of Event Scale – ID (IES-ID; traumagerelateerde klachten)
in. Daarnaast vulden naastbetrokkenen (familieleden of begeleiders)
de Angst-, Depressie- en Stemmingsschaal (ADESS; angst, depressie
en stemmingsproblemen) en de Inventarisatie van Gedragsproblemen
(IGP; frequentie en ernst van probleemgedrag) in. Voor het vaststellen
van de interbeoordelaarsbetrouwbaarheid werden 35 video-opnamen
van het DITS-LVB-interview willekeurig geselecteerd. Een tweede,
onafhankelijke, beoordelaar scoorde alle items van de gebeurtenissen-
en symptoomsectie van de DITS-LVB en beoordeelde of een gebeurtenis
voldeed aan het A-criterium en of er sprake was van een PTSS-classificatie.
De resultaten laten zien dat de interbeoordelaarsbetrouwbaarheid goed
tot uitstekend is voor de PTSS-symptomen, de beoordeling van potentieel
traumatische gebeurtenissen (criterium A), en de PTSS-classificatie. Ook
de constructvaliditeit van de DITS-LVB bleek goed: er werd een positieve
samenhang gevonden tussen PTSS-symptoomscores en een PTSS-
classificatie en de scores op de BSI-18, IES-ID en ADESS, terwijl alleen
de PTSS-symptoomscores positief samenhingen met de ernst van
gedragsproblemen op de IGP. Opvallend was dat 58% van de deelnemers
voldeed aan de DSM-5-TR criteria voor PTSS volgens de DITS-LVB.
Voorafgaand aan deelname aan het onderzoek was dit bij slechts 7%
geregistreerd in het elektronisch cliëntdossier.
Hoofdstuk 3 beschrijft de ontwikkeling van de zelfrapportage- en
proxyversie van de Trauma Screener – LVB (TS-LVB) voor volwassenen.
Daarnaast wordt het onderzoek naar de psychometrische kenmerken
van de TS-LVB beschreven. De TS-LVB werd ontwikkeld door de Kinder
en Jeugd Trauma Screener aan te passen voor volwassenen met een
LVB. Aanpassingen waren gebaseerd op klinische expertise van de
onderzoeksgroep en wetenschappelijke literatuur, en verder aangescherpt
via focusgroepen met volwassenen met een LVB, hun ouders, begeleiders
en gedragswetenschappers die ervaring hadden met PTSS bij mensen met
een LVB. Daarna werden de zelfrapportageversie en de proxyversie van de
TS-LVB in een pilotfase afgenomen bij volwassenen met een LVB en hun
begeleiders en ouders. Hierbij werd de begrijpelijkheid en toepasbaarheid
S
153]]></page><page Index="156" isMAC="true"><![CDATA[Appendices
van beide versies beoordeeld. Op basis van de pilotfase werden geen
verdere aanpassingen gemaakt.
Vervolgens werden in een grotere steekproef de psychometrische
kenmerken van de TS-LVB onderzocht. De zelfrapportageversie van de TS-
LVB werd ingevuld door 97 volwassenen met een LVB, en de proxyversie
door 92 naastbetrokkenen (familieleden of begeleiders) van volwassenen
met een LVB. De uitkomsten werden vergeleken met een PTSS-classificatie
als vastgesteld met de DITS-LVB (versie voor volwassenen). Resultaten
lieten zien dat de zelfrapportageversie van de TS-LVB een uitstekende
interne consistentie had en een zeer goede validiteit voor het onderscheiden
van volwassenen met en zonder PTSS. Een afkapscore van 18 bleek
optimaal voor het voorspellen van een PTSS-classificatie. De proxyversie
van de TS-LVB bleek wel intern consistent, maar kon in deze steekproef
PTSS niet valide onderscheiden. Op basis van de resultaten kan worden
geconcludeerd dat de zelfrapportageversie van de TS-LVB een betrouwbaar
en valide instrument is voor het screenen van PTSS bij volwassenen met
een LVB. De beperkte validiteit van de proxyversie wijst erop dat begeleiders
onvoldoende zicht hebben op PTSS bij volwassenen met een LVB. Hierdoor
blijft zelfrapportageversie van de TS-LVB essentieel voor het signaleren van
PTSS in deze doelgroep.
Hoofdstuk 4 beschrijft het onderzoek naar de veiligheid en effectiviteit
van kortdurende intensieve EMDR-therapie bij volwassenen met een LVB,
PTSS en ernstige gedragsproblemen. Twaalf volwassenen met een LVB,
PTSS en ernstige gedragsproblemen namen deel aan dit onderzoek.
Zij kregen tweemaal per dag (in de ochtend en middag), vier dagen
per week, gedurende twee weken EMDR-therapie. De therapie werd
gegeven door een team van zes verschillende (roterende) therapeuten.
Elf deelnemers rondden de behandeling af, één deelnemer stopte
voortijdig. Primaire uitkomstmaten waren PTSS-symptomen, PTSS-
diagnose en de veiligheid van de behandeling. Secundaire uitkomstmaten
waren gedragsproblemen, adaptieve vaardigheden en het gebruik van
vrijheidsbeperkende maatregelen. Er vonden metingen plaats vóór, tijdens
en na de behandeling en bij follow-up, zes weken, negen weken en vier
maanden na de behandeling. PTSS-symptomen namen na de kortdurende
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intensieve EMDR-therapie bij alle volwassenen af en negen van de elf
volwassenen voldeden na afronding van de behandeling en bij de laatste
follow-up meting niet meer aan de DSM-5-TR criteria voor PTSS. Op basis
van het uitblijven van geregistreerde veiligheid gerelateerde gebeurtenissen
werd de behandeling als veilig beoordeeld. Er werden geen veranderingen
gevonden in gedragsproblemen, adaptieve vaardigheden en het gebruik
van vrijheidsbeperkende maatregelen.
Hoofdstuk 5 beschrijft een kwalitatief onderzoek naar de ervaringen van
drie volwassenen met een LVB, PTSS en ernstige gedragsproblemen
met de kortdurende intensieve EMDR-therapie met zes verschillende
(roterende) therapeuten. Drie volwassenen die ook deelnamen aan de studie
beschreven in hoofdstuk 4 werden vóór en na de behandeling geïnterviewd
met behulp van semigestructureerde interviews. Hun begeleiders werden
eveneens vóór en na de behandeling geïnterviewd, terwijl de EMDR-
therapeuten alleen na afloop van de behandeling werden geïnterviewd.
Daarnaast werden notities die tijdens het onderzoek waren gemaakt
gebruikt om de context van de behandeling te verduidelijken. Deelnemers
gingen de behandeling in met hoge verwachtingen over de mate waarin
EMDR-therapie hun dagelijks leven zou kunnen veranderen. Eén deelnemer
stopte vroegtijdig met de therapie, terwijl twee deelnemers de volledige
behandeling afrondden. Het intensieve format van het programma werd
door alle deelnemers als zwaar ervaren, maar alle deelnemers beschreven
deze opzet tegelijkertijd als ondersteunend. De intensiteit zorgde voor
continuïteit en hielp hen betrokken te blijven bij de behandeling. Het
werken met roterende therapeuten werd door twee deelnemers als positief
ervaren; de derde deelnemer had geen positieve of negatieve ervaring. Uit
de interviews blijkt dat de betrokkenheid van het professionele netwerk
tijdens de therapie beperkt was.
Hoofdstuk 6 bevat de algemene discussie, waarin twee kernbevindingen
van dit proefschrift worden beschreven. Een eerste kernbevinding is dat
PTSS bij volwassenen met een LVB beter kan worden herkend wanneer
gebruik wordt gemaakt van de TS-LVB. De tweede kernbevinding is dat
kortdurende intensieve EMDR-therapie met roterende therapeuten in
onderhavig onderzoek effectief was voor de behandeling van PTSS bij de
S
155]]></page><page Index="158" isMAC="true"><![CDATA[Appendices
deelnemers met een LVB, PTSS en ernstige gedragsproblemen. Samen
laten de studies in dit proefschrift zien dat PTSS bij volwassenen met een
LVB beter kan worden herkend en effectief behandeld.
De bevindingen in dit proefschrift geven aanleiding tot vervolgonderzoek naar
een aantal onderwerpen. Allereerst wordt geadviseerd om de sensitiviteit
van de TS-LVB voor het meten van verandering in PTSS-symptomen
over tijd te onderzoeken, om vast te stellen of het instrument geschikt is
voor het monitoren en evalueren van effecten van traumabehandeling.
Daarnaast wordt geadviseerd om de psychometrische kenmerken van de
TS-LVB in meer diverse populaties en zorgsettingen te onderzoeken, zodat
de generaliseerbaarheid van de conclusies kan worden vergroot. Tevens
wordt geadviseerd om een traumascreener te ontwikkelen en valideren
voor kinderen en adolescenten met een LVB. Verder wordt aanbevolen
om in een gerandomiseerde gecontroleerde studie intensieve EMDR-
therapie te vergelijken met EMDR-therapie die wordt aangeboden in een
wekelijks en minder intensieve opzet, om de relatieve effectiviteit van
beide behandelvormen vast te stellen. Tot slot wordt geadviseerd om te
onderzoeken in hoeverre en onder welke voorwaarden een afname van
PTSS-symptomen leidt tot veranderingen in adaptief functioneren en
gedragsproblemen, met specifieke aandacht voor de rol van begeleiders en
omgevingsfactoren.
Dit proefschrift laat zien dat PTSS bij volwassenen met een LVB beter kan
worden herkend met specifiek aangepaste en gevalideerde instrumenten,
zoals de DITS-LVB en de TS-LVB. In dit onderzoek namen na kortdurende
intensieve EMDR-therapie met roterende therapeuten de PTSS-symptomen
af en voldeed een groot deel van de deelnemers na de behandeling en bij
follow-up niet meer aan de DSM-5-TR-criteria voor PTSS. De casus van Hilda
laat zien hoe PTSS bij volwassenen met een LVB jarenlang onopgemerkt kan
blijven en hoe reguliere, wekelijkse traumabehandeling niet altijd haalbaar
is. De bevindingen in dit proefschrift tonen dat vroegtijdige signalering,
gestructureerde diagnostiek en intensieve traumagerichte behandeling
in samenhang kunnen bijdragen aan een meer tijdige en passende
behandeling.
156]]></page><page Index="159" isMAC="true"><![CDATA[]]></page><page Index="160" isMAC="true"><![CDATA[]]></page><page Index="161" isMAC="true"><![CDATA[Research data management and
privacy statement]]></page><page Index="162" isMAC="true"><![CDATA[]]></page><page Index="163" isMAC="true"><![CDATA[Research data management and privacy statement
Ethical statement and privacy statement
This research was conducted in compliance with the General Data
Protection Regulation (GDPR) and all applicable laws and ethical guidelines.
The Medical Research Ethics Committee of the East Netherlands (reference
number: 2020-6967- NL75909.091.20) has approved to conduct alle
studies.
The privacy of participants of all studies has been warranted using random
individual participant IDs. Encrypted pseudonymization key files linking
these random participant IDs with identifiable personal information were
stored on a secure network drive of Radboud University and were only
accessible to Robert Didden and Anne Versluis. The key files for all studies
were destroyed within one month after data processing was completed.
Video recordings (study 1, Chapter 2) were deleted after the second rater
had scored the interviews. Audio recordings (study 4, Chapter 5) were
deleted after a transcript had been made. Consent forms for all studies and
all research data resulting from this dissertation, are stored on a secure
network drive of Radboud University.
Funding
The research of this dissertation was funded by Scientific Research
Foundation ‘s Heeren Loo (grant number 15003) and ZonMw, Netherlands
Organization for Health Research (grant number 641001103).
Data management and availability
Radboud University and the Behavioural Science Institute (BSI) have set
strict conditions for the management of research data. Research data
management was conducted according to the FAIR principles. All research
data resulting from this dissertation were handled in accordance with
the university’s research data management policy (https://www.ru.nl/
rdm/) and the BSI’s research data management protocol (https://www.
radboudnet.nl/bsi/rdm). Data are not publicly available due to privacy of
research participants. Data are available on reasonable request from the
corresponding author.
R
161]]></page><page Index="164" isMAC="true"><![CDATA[]]></page><page Index="165" isMAC="true"><![CDATA[Dankwoord]]></page><page Index="166" isMAC="true"><![CDATA[]]></page><page Index="167" isMAC="true"><![CDATA[Dankwoord
Dit proefschrift was niet mogelijk geweest zonder de steun, inzet en
betrokkenheid van velen. Graag wil ik een aantal mensen in het bijzonder
bedanken.
Allereerst wil ik alle mensen met een verstandelijke beperking bedanken
die ik in de afgelopen jaren heb ontmoet. Jullie verhalen, ervaringen en
openheid vormden de inspiratie voor dit proefschrift.
Ik wil mijn promotoren en copromotor graag bedanken voor hun
begeleiding gedurende dit promotietraject.
Robert Didden, dank je wel voor alles wat je voor mij en voor dit proefschrift
hebt betekend. In jouw begeleiding stond jouw brede kennis van onderzoek bij
mensen met een licht verstandelijke beperking centraal. Je begeleidingsstijl
is prettig: kritisch waar nodig, met voldoende ruimte voor eigen keuzes. Je
liet mij groeien in mijn rol als onderzoeker en maakte mij vertrouwd met
het wetenschappelijk schrijven. Daarbij leerde je mij scherp te kijken naar
de werkelijke betekenis van onderzoeksresultaten en om niet meer en niet
minder te concluderen dan we daadwerkelijk hadden onderzocht.
Liesbeth Mevissen, ik ben je veel dank verschuldigd. Jouw onderzoeken
naar PTSS bij mensen met een verstandelijke beperking vormden het
fundament waarop ik verder kon bouwen. In jouw begeleiding kwamen
jouw sterke conceptuele denken over trauma, PTSS en EMDR-therapie
en je diepgaande kennis en ervaring met mensen met een verstandelijke
beperking samen. Dit leverde een belangrijke bijdrage aan de inhoud van
dit proefschrift. Dank je wel voor je betrokkenheid, scherpte en vertrouwen.
Carlo Schuengel, dank je wel voor de manier waarop jij jouw kennis over
wetenschappelijk onderzoek met mij hebt gedeeld. Op momenten waarop
ik dacht dat alles was beantwoord en zorgvuldig beschreven, kwam jij met
nieuwe literatuur, vragen of suggesties die het onderzoek verder verdiepten
en aanscherpten. In de loop der jaren keek ik steeds meer uit naar wat
je zou inbrengen, wetende dat niet alleen de teksten, maar ook ikzelf als
onderzoeker daardoor groeide.
D
165]]></page><page Index="168" isMAC="true"><![CDATA[Appendices
Ad de Jongh, dank je wel voor jouw tomeloze enthousiasme, betrokkenheid
en vertrouwen. Je keek steeds vanuit mogelijkheden en liet zien hoe lef en
nieuwe inzichten richting kunnen geven aan wetenschappelijk onderzoek.
Dankzij jouw brede kennis en ervaring met EMDR-therapie dacht je mee
vanuit de nieuwste ontwikkelingen, en wat daarin wel mogelijk is voor
mensen met een verstandelijke beperking. Je combineerde waardering met
uitdaging en moedigde mij aan om gefocust te blijven op mijn eigen koers.
Zoals jij het formuleerde: “Speel altijd je eigen bal.”
Nienke Peters-Scheffer en Lianne Bakkum, dank jullie wel voor de
belangrijke bijdrage die jullie als coauteurs en experts hebben geleverd aan
twee hoofdstukken van dit proefschrift.
De leden van de manuscriptcommissie, prof. dr. Elisa van Ee, prof. dr.
Ramón Lindauer, dr. Carlijn de Roos, prof. dr. Thérèse van Amelsvoort en
prof. dr. Paul van der Heijden, wil ik bedanken voor het beoordelen van mijn
manuscript.
De ideeën voor dit proefschrift ontstonden tijdens mijn deelname aan de
masterclass van de VGN. Sabina Kef was één van de docenten van deze
masterclass en had mij eerder begeleid tijdens mijn M-these, toen ik
orthopedagogiek studeerde. De masterclass wakkerde mijn enthousiasme
voor onderzoek opnieuw aan en vormde het startpunt van dit proefschrift.
Sabina, dank je wel voor de rol die je daarin hebt gespeeld. Je liet mij
zien hoe onderzoek kan ontstaan uit nieuwsgierigheid en hoe relevantie,
wetenschappelijk, maar vooral ook maatschappelijk, daarin een centrale
plek kan krijgen. Het voelt bijzonder dat je bij mijn verdediging als opponent
zult optreden en daarmee opnieuw een rol speelt in mijn academische
ontwikkeling.
Mijn paranimfen, Mariëlle Rouleaux en Annemieke Hoogstad, wil ik bedanken
voor alles wat we samen hebben gedeeld in de afgelopen jaren. Voor het
samen optrekken in onze onderzoeken, het delen van kennis en ervaringen,
het meeleven en relativeren. Jullie waren altijd dichtbij, voor inhoudelijke
gesprekken en talloze telefoontjes. Er was vaak ruimte voor humor; wat
hebben wij veel gelachen. De congressen, presentaties, workshops en de
166]]></page><page Index="169" isMAC="true"><![CDATA[Dankwoord
schrijfweek die we samen hadden, maken daar onlosmakelijk deel van uit.
Ik hoop dat we dit in de toekomst voortzetten.
Ik ben grote dank verschuldigd aan alle cliënten, begeleiders, ouders, broers,
zussen en gedragswetenschappers die in de afgelopen jaren hebben
meegedaan aan de onderzoeken. Dank jullie wel voor jullie grote bereidheid
om deel te nemen; door jullie inzet, tijd en openheid was dit onderzoek
mogelijk.
De therapeuten van het therapeutenteam, José Brummel, Sonja Helwegen,
Sanne Vijlbrief, Miranda van Es, Marsha van Zandwijk-van Brummelen,
Mariëlle Rouleaux en Marjolein Jansen, wil ik bedanken. Dank jullie wel voor
jullie expertise, inzet en flexibiliteit, die onmisbaar waren voor het uitvoeren
van dit onderzoek.
Mijn collega’s uit de regio Ermelo wil ik bedanken voor het meedenken, het
sparren en het betrokken blijven, ook in de periode waarin ik steeds minder
aanwezig was op locatie. Peter Lauteslager, mijn leidinggevende toen ik
met dit onderzoek startte, dank je wel voor de ruimte en het vertrouwen dat
je mij gaf om dit onderzoek te beginnen. Ook dank aan de leidinggevenden
die daarna volgden, Tjitske Koopman, Sjoerd van Boggelen en Julie van der
Horst-Weltens, van wie ik ruimte kreeg om dit onderzoek voort te zetten.
Binnen ’s Heeren Loo wordt het belang van onderzoek, gericht op het
versterken van de praktijk en het verder ontwikkelen van wetenschappelijke
inzichten, onderkend. Bas Bijl, dank je wel; door jouw inzet kreeg onderzoek
een duidelijke plek in de organisatie.
Mijn collega’s van zorgbeleid en bedrijfsvoering in Amersfoort wil ik
bedanken voor het meedenken, de support en voor het laten zien hoe
onderzoek aan impact wint door het te verbinden aan beleid.
Paul Jochems en Fried Böhmer, directie van Advisum, wil ik bedanken
voor het vertrouwen en de ruimte die zij geven om in een volgende stap
wetenschappelijk onderzoek, psychotraumazorg en kennisdeling duurzaam
samen te brengen in een academisch centrum voor psychotrauma.
D
167]]></page><page Index="170" isMAC="true"><![CDATA[Appendices
Een bijzonder dankwoord is voor Edith Rijnsburger. Jij speelde een
belangrijke rol in het telkens weer terugbrengen van onderzoeksresultaten
naar de praktijk. Door jou heb ik geleerd hoe cruciaal communicatie daarin
is: bevindingen moeten niet alleen worden gedeeld, maar ook begrepen en
benut. Dankzij jouw inzet werden resultaten op het juiste moment en op de
juiste manier onder de aandacht gebracht. Daardoor bleef dit onderzoek
niet beperkt tot publicaties, maar kan het daadwerkelijk verschil maken
voor het werkveld, voor professionals die werken met mensen met een
verstandelijke beperking en PTSS, en uiteindelijk voor de mensen om wie
het gaat.
Ik wil Louise Poot van ‘Paspartoe’, atelier van ’s Heeren Loo in Noordwijk,
bedanken voor het ontwerp van de cover van dit proefschrift. Met dit beeld
wist zij op een treffende manier te verbeelden waar dit proefschrift over
gaat. Over haar schilderij “Vrij zijn”, schreef Louise: “Dit schilderij gaat over
het achterlaten van trauma’s en het vrij zijn daarvan. De vogels in het haar
staan symbool voor het verjagen van de trauma’s. Daardoor is zij echt vrij
van alles.”
Ik wil mijn collega’s van de academische werkplaats Viveon bedanken.
Dank voor het samen nadenken over onderzoek, elkaar inspireren en scherp
houden, en voor het plezier dat we met elkaar hadden buiten het onderzoek
om.
Mijn vader wil ik bedanken, hij werkte zijn leven lang voor mensen met een
verstandelijke beperking en heeft mij geleerd om in het werk altijd de cliënt
centraal te stellen. Dat uitgangspunt heb ik gedurende het hele project in
mijn achterhoofd gehouden.
Ik wil mijn familie en vrienden bedanken. Dank voor jullie interesse en
betrokkenheid, voor de gesprekken waarin ik jullie regelmatig mocht
lastigvallen met mijn onderzoek, en voor het meeleven op afstand of
dichtbij. Dat jullie wilden luisteren, meedachten en vroegen hoe het ging,
maakte verschil. Een promotietraject is tenslotte geen negen-tot-vijfbaan.
Liza, jij in het bijzonder: dank dat je er altijd bent, in de grote momenten,
maar juist ook in de kleine, alledaagse.
168]]></page><page Index="171" isMAC="true"><![CDATA[Dankwoord
Tot slot wil ik mijn gezin bedanken, mijn lieve man Jerom, en mijn kinderen
Bram, Elin en Tom. Ook thuis was dit geen negen-tot-vijfbaan, en kwamen
ideeën soms op onverwachte momenten. Dat ik daar ruimte voor kreeg,
zegt veel. Jullie hebben van dichtbij meegemaakt dat ik bezig was met een
groot en voor mij belangrijk project. De verontwaardiging van mijn oudste
zoon Bram was dan ook groot toen ik hem vertelde hoeveel pagina’s mijn
boek uiteindelijk zou tellen: “Mam, dan heb je misschien één of twee zinnen
per dag geschreven in al die jaren.” Die relativering neem ik met liefde mee.
D
169]]></page><page Index="172" isMAC="true"><![CDATA[]]></page><page Index="173" isMAC="true"><![CDATA[List of publications]]></page><page Index="174" isMAC="true"><![CDATA[]]></page><page Index="175" isMAC="true"><![CDATA[List of publications
Peer-reviewed publications
Publications related to this dissertation
Versluis, A., de Jongh, A., Mevissen, L., Schuengel, C., Bakkum, L., & Didden,
R. (2025). Brief intensive EMDR therapy for PTSD in adults with
mild intellectual disability or borderline intellectual functioning and
behavioural problems: a multiple baseline design study. European
Journal of Psychotraumatology, 16(1), 2495642. https://doi.org/10.1
080/20008066.2025.2495642
Versluis, A., Mevissen, L., de Jongh, A., Schuengel, C., & Didden, R. (2025).
Reliability and validity of the Diagnostic Interview Trauma and
Stressors–Intellectual Disability in adults with mild intellectual
disabilities or borderline intellectual functioning. Journal of Mental
Health Research in Intellectual Disabilities, 18(2), 204–220. https://
doi.org/10.1080/19315864.2024.2416694
Versluis, A., Peters-Scheffer, N., Schuengel, C., Mevissen, L., de Jongh,
A., & Didden, R. (2025). Brief intensive EMDR therapy with rotating
therapists: Experiences of adults with mild intellectual disability or
borderline intellectual functioning, PTSD, and severe behavioural
problems. European Journal of Trauma & Dissociation, 9, 100610.
https://doi.org/10.1016/j.ejtd.2025.100610
Versluis, A., Schuengel, C., Mevissen, L., de Jongh, A., & Didden, R. (2025).
Development and evaluation of the Trauma Screener-Intellectual
Disability: a post-traumatic stress disorder screening tool for adults
with mild intellectual disability or borderline intellectual functioning.
Journal of Intellectual Disability Research, 69(2), 127–136. https://doi.
org/10.1111/jir.13198
Other publications
Bierman, T., Versluis, A., Korzilius, H., & Didden, R. (2026). Feasibility of
intensive eye movement desensitization and reprocessing therapy
for adults with mild intellectual disability or borderline intellectual
functioning and posttraumatic stress disorder in a tertiary mental
health care setting: A nonconcurrent single-case design study.
P
173]]></page><page Index="176" isMAC="true"><![CDATA[Appendices
Journal of Mental Health Research in Intellectual Disabilities. https://
doi.org/10.1080/19315864.2026.2618075.
Boone, D*., Versluis, A*., Delforterie, M., & Didden, R. (2026). Sexual and
non-sexual trauma in relation to PTSD in people with mild intellectual
disabilities or borderline intellectual functioning. https://doi.org/10.10
80/19315864.2026.2655129
* These authors contributed equally to this work.
Hoogstad, A., Peters-Scheffer, N., Rouleaux, M. Mevissen, L., Versluis, A.,
& Didden, R. (2025) Screening and Assessment of Posttraumatic
Stress Disorder in Individuals with Intellectual Disabilities: A Scoping
Review. Advances in Neurodevelopmental Disorders, 9, 465-478.
https://doi.org/10.1007/s41252-025-00441-5
Non-peer reviewed publications
Didden, R., Hoogstad, A., Rouleaux, M., Versluis, A., & Mevissen, L.
(2023). Trauma en verstandelijke beperking. Sozio-Speciaal, Licht
Verstandelijke Beperking, 28(3), 69-74. https://www.sociaaldigitaal.
nl/p/trauma-en-verstandelijke-beperking/8559
Versluis, A. (2024), Onderzoek naar het herkennen van PTSS en de
effectiviteit van intensieve EMDR-therapie, EMDR Magazine, 12(34),
20-22. https://www.emdr-magazine.nl/2024-34/
Schipper-Eindhoven, A. & Versluis, A. (2021). Oog voor PTSS bij mensen
met een LVB.
Nurse Academy GGZ, 41-46. https://www.prelumacademy.nl/
vakmedia/nurse-academy-ggz/d373663b-0589-4d41-99ba-
4d9cdc5b0fdd
174]]></page><page Index="177" isMAC="true"><![CDATA[List of publications
Interviews
Eppink, R. (2024). PTSS herkennen een behandelen bij mensen met een LVB
en ernstige gedragsproblemen. Klik Vakblad voor de Verstandelijk
Gehandicaptenzorg 3, 6. https://www.klik.org/nieuws/nieuws-item/t/
ptss-herkennen-en-behandelen-bij-mensen-met-een-lvb-en-ernstige-
gedragsproblemen
Jak, H., & Louwers, M. (2025). Beter zicht op trauma bij mensen met een
licht verstandelijke beperking. VGCt Magazine, (3), 7–9.
P
175]]></page><page Index="178" isMAC="true"><![CDATA[]]></page><page Index="179" isMAC="true"><![CDATA[Curriculum Vitae]]></page><page Index="180" isMAC="true"><![CDATA[]]></page><page Index="181" isMAC="true"><![CDATA[Curriculum Vitae
Anne studeerde van 2001 tot en met 2005 pedagogiek aan de Noordelijke
Hogeschool Leeuwarden. Na haar afstuderen vertrok zij voor enkele
maanden naar Kenia, waar zij werkte bij een woonvoorziening voor
kinderen met een lichamelijke beperking. Terug in Nederland ging zij aan
het werk bij Heideheuvel in Hilversum, waar zij werkte op kinderafdelingen
voor kinderen met chronische gezondheidsproblemen. Van 2007 tot en met
2009 studeerde zij orthopedagogiek aan de Vrije Universiteit in Amsterdam.
Tijdens deze studie werkte zij als begeleider op de opnameafdeling voor
kinderen en jongeren (Fornhese) van GGZ Centraal in Amersfoort. In 2009
startte zij als orthopedagoog bij orthopedagogisch-didactisch centrum Het
Lumeijn. Daar was zij verantwoordelijk voor orthopedagogische diagnostiek
en advisering van leerlingen met leer- en gedragsproblemen op middelbare
scholen in Zwolle en omgeving.
Sinds 2012 werkt Anne als gedragswetenschapper bij ’s Heeren Loo in
Ermelo. Tot en met 2020 vervulde zij daar de rol van regiebehandelaar voor
mensen met een verstandelijke beperking en moeilijk verstaanbaar gedrag.
In dezelfde periode volgde zij de opleiding tot gezondheidszorgpsycholoog
(2013–2016) en rondde zij in 2016 de basisopleiding EMDR (kind en jeugd)
af. In deze jaren ontstond haar belangstelling voor trauma en PTSS, met
name bij mensen met een verstandelijke beperking en moeilijk verstaanbaar
gedrag. Zij volgde in 2018 de vervolgopleiding EMDR (kind en jeugd) en
werd in 2020 geregistreerd als EMDR-therapeut VEN®.
Tijdens haar studie orthopedagogiek was haar interesse in wetenschappelijk
onderzoek gewekt; een belangstelling die zij naast haar klinische werk bleef
behouden. Van 2018 tot en met 2019 nam zij deel aan de masterclass
Wetenschappelijk Onderzoek in de Gehandicaptenzorg van de Vereniging
Gehandicaptenzorg Nederland. In deze periode kwamen haar interesse in
mensen met een verstandelijke beperking en moeilijk verstaanbaar gedrag,
haar focus op trauma en PTSS en haar wetenschappelijke belangstelling
samen. Binnen deze masterclass schreef Anne een onderzoeksvoorstel,
dat de eerste aanzet vormde voor het promotieonderzoek dat zij in 2020
startte bij het Behavioural Science Institute van de Radboud Universiteit. De
resultaten van dit onderzoek staan beschreven in dit proefschrift.
CV
179]]></page><page Index="182" isMAC="true"><![CDATA[Appendices
Tijdens haar promotieonderzoek, en ook daarna, bleef Anne werkzaam als
EMDR-therapeut VEN® bij ’s Heeren Loo. Als programmamanager werkt
zij aan de ontwikkeling van een academisch centrum voor psychotrauma.
Bij de academische werkplaats Viveon is zij betrokken bij het uitvoeren en
initiëren van vervolgonderzoek. Tevens is zij bestuurslid van de Vereniging
EMDR Nederland.
180]]></page><page Index="183" isMAC="true"><![CDATA[Trauma Screener – Licht Verstandelijke Beperking (TS-LVB) voor volwassenen]]></page><page Index="184" isMAC="true"><![CDATA[De cover van dit proefschrift is geschilderd door Louise Poot. Zij werkt bij
‘Paspartoe’ atelier van ’s Heeren Loo in Noordwijk. Over haar schilderij “Vrij
zijn”, schreef Louise: “Dit schilderij gaat over het achterlaten van trauma’s en het
vrij zijn daarvan. De vogels in het haar staan symbool voor het verjagen van de
trauma’s. Daardoor is zij echt vrij van alles.”]]></page></pages></Search>