Rates of comorbid symptoms in children with ASD, ADHD, and comorbid ASD and ADHD

•The study examined comorbid rates in ASD, ADHD and comorbid ASD + ADHD group.•Comorbid ASD + ADHD group evinced higher rates of comorbid symptoms.•Comorbid ASD + ADHD group endorsed more severe comorbid symptoms.

The current diagnostic criteria do not allow co-diagnosis of autism spectrum disorder (ASD) and attention deficit/hyperactivity disorder (ADHD). As a result, there has been little research on how these two disorders co-occur in the ASD population. The current study aimed to extend the literature in this area by examining comorbid rates in three different diagnostic groups (ASD, ADHD, and comorbid ASD + ADHD) using the Autism Spectrum Disorders-Comorbidity for Children (ASD-CC). Children with comorbid ASD and ADHD evinced higher rates of comorbid symptoms than children with ASD or ADHD alone. Additionally, children with comorbid ASD and ADHD endorsed more severe comorbid symptoms. Implications regarding these findings are discussed.