Factor Structure of Repetitive Behaviors Across Autism Spectrum Disorder and Attention-Deficit/Hyperactivity Disorder

Restricted interests and repetitive behaviors (RRBs) are core symptoms of autism spectrum disorder (ASD), and commonly occur in attention-deficit/hyperactivity disorder (ADHD). Little is known about how RRBs manifest in ADHD. We quantified and compared factor structures of RRBs in children with ASD (n = 634) or ADHD (n = 448), and related factors to sex and IQ. A four-factor solution emerged, including Stereotypy, Self-Injury, Compulsions, and Ritualistic/Sameness. Factor structures were equivalent across diagnoses, though symptoms were more severe in ASD. IQ negatively correlated with Stereotypy, Self-Injury, and Compulsions in ASD, and negatively correlated with Compulsions and Ritualistic/Sameness behaviors in ADHD. In ASD only, females exhibited higher Self-Injury. Thus, patterns of RRBs are preserved across ASD and ADHD, but severity and relationship with IQ differed.

Automated summary

Restricted interests and repetitive behaviors (RRBs) are core symptoms of both autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD), with similar factor structures observed in both disorders but more severe symptoms in ASD, as well as differences in the relationship with IQ.