PhD Defense Siri Noordermeer – June 26th, 15.45

ADHD is a relatively common disorder in child and adolescent psychiatry. Although much research has been and is being done into ADHD, findings in the areas of neurocognitive functioning and of the brain are still unclear. A possible explanation for this may be that in earlier research (almost) none of the studies took one of the most common comorbid disorders into account: ODD, oppositional defiant disorder. Since ODD itself is also associated with both impairments in neurocognitive functioning and with differences in the brain, this may have influenced previous findings regarding ADHD.
                Based on the results discussed in the current dissertation, it can be argued that previous studies not taking ODD into account may have led to the problems that are present in individuals with ADHD being incorrectly assigned to ADHD symptoms, rather than to the ODD symptoms. For example, it appears that emotion recognition problems are only present in the group of adolescents and young adults with both ADHD and ODD, and not in the group with only ADHD. In addition, it appears that the group with both ADHD and ODD is faced with a double burden: this group shows stronger impairments in terms of their neurocognitive functioning as well as larger and more widespread differences in brain structure. More specifically, this group with both disorders not only shows impairments in (among others) working memory and emotion recognition, but also shows more and larger structural brain differences than the group with ADHD alone.
                Taken together, previous research in which ADHD and ODD were combined seems to have resulted in an overestimation of the impairments and difficulties associated with ADHD, since it appears that ODD actually carries a part of those impairments and difficulties. Thus, both in scientific research and in clinical practice, the presence of ODD in individuals with ADHD should be taken into account, as this combination is associated with more impairments in neurocognitive functioning and more and larger differences in brain structure. These impairments may result in serious difficulties in daily functioning, for example at home or at school, as well as in difficulties in the (behavioural) treatment of the problem. dlocked0 Grid