An exploratory investigation of key clinical and neuropsychological characteristics in children and adolescents with Attention Deficit Hyperactivity Disorder (ADHD) and/or Obsessive Compulsive Disorder (OCD)

Attention-Deficit Hyperactivity Disorder (ADHD) and Obsessive-Compulsive Disorder (OCD) are prevalent childhood disorders that are often comorbid. This thesis investigated demographic characteristics (including academic and intellectual functioning, parental psychopathology, family functioning, and social adversity status), clinical characteristics (parent and child-reported ratings of symptom severity), and the neuropsychological executive function profiles of visuospatial attention and memory constructs using a battery of computerised tests in age-matched children and adolescents between 7 to 16 years of age with a diagnosis of ADHD (n = 35), OCD (n = 29), comorbid ADHD and OCD (n = 34) compared with healthy control children (n = 32). The results indicate that children and adolescents with ADHD or OCD were qualitatively different on key phenomenological variables, while the comorbid ADHD and OCD group generally had additive symptomatology that reflected the independent contribution of symptomatic and functional impairment from each disorder. Children and adolescents with ADHD and/or OCD displayed shorter spatial spans compared to healthy control children. Relative to healthy control participants, both the ADHD group and comorbid ADHD and OCD group performed significantly worse on visuospatial spatial working memory and short-term recognition memory tasks, while the ADHD group and OCD group displayed attentional set shifting deficits relative to the healthy control group. The neuropsychological profiles of children with ADHD or comorbid ADHD and OCD are characterised by similar patterns of frontostriatal-linked dysfunction. Specific set-shifting and spatial span deficits in the OCD group contrasted with their intact performance on other tests of executive function, such as spatial working memory and visuospatial short-term memory recognition, and suggested only limited frontostriatal-linked dysfunction.