Page 18 - Post-traumatic stress disorder in adults with mild intellectual disability: Screening, assessment, and brief intensive EMDR therapy

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