The risk for externalizing behaviors (Bos et al., 2018) complicates the comorbidity between autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). To investigate whether the relation between ASD status (ASD vs typical development, TD) and externalizing behaviors would vary by differences in ADHD symptoms, parent-child dyads (3-7yo), 127 TD (47.7% female) and 81 children with ASD (16.7% female), participated. The linear regression tested model with significant main and interaction effects explained 43.3% of variance, overall. Consistent with research, externalizing problems were higher for both groups when ADHD symptoms were also high compared to low, an effect stronger for TD children
