The neuropsychology of Conduct Disorder: the impact of comorbid Attention-Deficit/Hyperactivity Disorder

Conduct Disorder (CD) is characterised by a persistent and pervasive pattern of aggressive and antisocial behaviour that violates the rights of others or in which major age-appropriate societal norms are violated. Researchers have argued that this pattern of sensation-seeking behaviour stems from a higher threshold for emotional stimulation in children and adolescents with CD compared to typically-developing individuals. In addition, studies have found a reduced sensitivity to reward which interferes with the learning of appropriate behaviours. CD and AttentionDeficit/Hyperactivity Disorder (ADHD) are considered to be highly comorbid both in clinical and community samples. Research has indicated that individuals with CD+ADHD have poor social functioning, poor socio-economic outcomes later in life and are likely to drop-out or be kicked out of educational institutions. However, neuroscience research has not properly addressed the issues surrounding the effects of comorbid ADHD on cognitive and emotional processing in CD. Understanding these effects will allow us to develop more sophisticated causal pathways, which in the longer term may aid clinicians to administer treatments tailored specifically to patients’ individual needs.The present study investigated the effects of comorbid ADHD on the clinical and neuropsychological profiles of adolescents with CD, by comparing groups of adolescents with CD-only (CD-ADHD; n = 23), comorbid CD+ADHD (n = 28) and a typically-developing control group (TDC; n = 30). We used a range of clinical and questionnaire-based assessments, as well as a series of behavioural tasks that examined Executive Functions (EFs), facial emotion recognition and perspective-taking. We found that CD was independently associated with impairments in impulsive choice (“hot” EFs), whereas comorbid ADHD was associated with impairments in interference control and working memory (“cool” EFs). Furthermore, we found that a broad pattern of facial emotion recognition deficits was limited to those individuals with CD+ADHD. Our study was also the first study to explicitly investigate the impact of comorbid ADHD on perspective-taking in CD. Our results do not provide evidence for a deficit in perspective-taking in adolescents with CD, regardless of ADHD comorbidity. Considered together, these results provide some insight on the impact of ADHD on the neuropsychology of CD and can be useful to both researchers and clinicians when considering new research designs and clinical interventions