Objectives: To systematically characterize the occurrence of autistic traits in children with ADHD and their corresponding clinical features.
Methods: The parents of 78 typically developing children (TDC; 32 boys) and 75 children with ADHD (60 boys) between the ages of 7 and 17 years completed the Social Responsiveness Scale (SRS) to identify children with elevated autistic traits (T score = 60).To determine whether elevated SRS total score in ADHD is associated with items that probe specific aspects of PDD (versus items nonspecifically related to PDD), all SRS items were classified in four domains. Three domains mapped on PDD related symptoms: Social (S; 24 items), Communication (C; 8 items), Restricted/Repetitive Behaviors (R; 10 items), the fourth domain included SRS items not specifically related to PDD (23 items). Domain scores were computed as average of the items within a domain. The ADHD groups with and without autistic traits (ADHD+ and ADHD-,respectively), and the TDC were compared with respect to the four domains scores adjusting for ADHD severity ratings. Conners’ Parent Rating Scale and cognitive testing were also collected.
Results: Within the ADHD group, 31% (n=23) presented with elevated SRS scores. This ADHD+ subgroup scored significantly higher than the ADHD- subgroup on Conners’ ratings of Social Problems, Oppositionality, Hyperactivity, DSM-IV Hyperactive-Impulsive, and DSM-IV Total but not on Inattention. Across the four domains of SRS items, statistically significant differences were observed with TDC
Conclusions: 1) we confirmed that a substantial number of children with ADHD have elevated parent ratings of autistic traits. 2) Elevated ratings of autistic traits are not accounted for by items that are not specifically related to autism. 3) The children with ADHD and autistic traits display a more severe pattern of behavioral abnormalities. Future work using multiple informants should address the clinical relevance of the co-occurrence of autistic traits in children with ADHD