Page 17 - Age of onset of disruptive behavior of residentially treated adolescents -Sjoukje de Boer

Also, studies differ in the way disruptive behavior is assessed. Some studies for 1 instance use self report measures (e.g., Dandreaux & Frick, 2009; Sanford et al., 1999)
while others use official records of the first offence or conviction (e.g., Carroll et al.,
2006; Dean et al., 1996; Tibbetts & Piquero, 1999). And even within studies that use
self report measures, there are differences in respondents and in the measures used.
Some studies use self-reporting of the youngster (e.g., Veenstra, Lindenberg, Verhulst,
& Ormel, 2009), while other studies use self-reporting by parents or teachers (e.g.,
Eyberg, Nelson, & Boggs, 2008; Frick et al., 1993; Moffitt, 1993; Sanders, Markie-
Dadds, Tully, & Bor, 2000).
Another complicating factor relates to the age of onset. Inconsistency characterizes the operational definition of early-onset versus adolescent-onset, with age cut-offs ranging from 10 (APA, 2000; Sanford et al., 1999) to 14 (Tibbetts & Piquero, 1999). Choices are often made based on pragmatic criteria (Simons, Wu, Conger, & Lorenz, 1994), and are related to the data available. When comparing studies, it is crucial to be aware of these differences (Dean et al., 1996). In the present thesis, disruptive behavior starting before age 12 was considered early-onset (EO), and disruptive behavior starting at age 12 or later was considered adolescent-onset (AO). This age cut-off was in accordance with Moffitt (1993; Moffitt et al., 1996), and with Dean (Dean et al., 1996), who found that differences between the EO and AO groups were evident when the threshold was set to age 12.
Not surprisingly, the research of Moffitt and colleagues has substantially influenced the DSM-IV classification of conduct disorder, resulting in two subtypes: Childhood-onset and Adolescent-onset conduct disorder (American Psychiatric Association, 1994; APA, 2000). Already for decades, academics and practitioners alike are searching for criteria to assess severity of conduct disorder. Although the DSM age of onset subtyping probably has considerable overlap with the EO and AO constructs of the present thesis, they are not the same. In the case of Childhood-onset conduct disorder, the diagnostician has to indicate whether the individual shows at least one symptom characteristic of conduct disorder prior to age 10 years. In the present thesis, a specific type of disruptive behavior (Frick et al., 1993) was considered present based on the age at which help was sought because of the behavior, special education was
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