Oppositional Defiant Disorder in Autism and ADHD.

Our study compared oppositional defiant disorder (ODD) in children with autism to ADHD-Combined presentation and ADHD-Inattentive presentation. Mothers of 2,400 children 3-17 years old with autism and/or ADHD completed the Pediatric Behavior Scale. ADHD-Combined was most strongly associated with ODD, with an ODD prevalence of 53% in children with ADHD-Combined only. When autism was added to ADHD-Combined, prevalence increased to 62% and the ODD score increased significantly. Autism+ADHD-Inattentive, Autism Only, and ADHD-Inattentive Only had ODD prevalences of 28%, 24% and 14%. In each diagnostic group, ODD had the same two factors (irritable/angry and oppositional/defiant); demographic differences between children with and without ODD were few; and correlations between ODD and conduct problems were large, correlations with depression were medium, and correlations with anxiety were small. However, ODD scores differed significantly between groups (Autism+ADHD-Combined > ADHD-Combined Only > Autism+ADHD-Inattentive and Autism Only > ADHD-Inattentive Only). The irritable/angry ODD component was greater in Autism+ADHD-Combined than in ADHD-Combined Only, whereas the oppositional/defiant component did not differ between the two groups. Autism was a significant independent risk factor for ODD, particularly the irritable/angry ODD component, but ADHD-Combined was the strongest risk factor. Therefore, the high co-occurrence of ADHD-Combined in autism (80% in our study) largely explains the high prevalence of ODD in autism. ADHD-Combined, autism, and ODD are highly comorbid (55-90%). Clinicians should assess all three disorders in referred children and provide evidence-based interventions to improve current functioning and outcomes for children with these disorders and reduce family and caretaker stress.