Are ADHD Traits Dissociable From the Autistic Profile? Links Between Cognition and Behaviour

Background: Autism and ADHD appear to show a degree of behavioural, cognitive and genetic overlap. It is not clear whether these are co-occurring disorders or whether they share some neural and cognitive features which lead to similarities in behavioural profiles.

Objectives: To identify the presence of ADHD related behaviours in a sample of children with ASD, and their relationship with the ASD triad of impairments symptoms and related cognitive impairments.

Methods: A semi-structured interview (3Di) elicited parental reports of ASD and ADHD symptoms. Children (n = 53) completed a comprehensive battery of cognitive assessment.

Results: 90% of children were reported to display significant levels of hyperactivity, impulsivity or inattention. Only one child showed above threshold levels of each ADHD component.

ADHD traits were significantly related to the ASD triad. Social interaction correlated with both hyperactivity and impulsivity. Communication correlated with inattention, hyperactivity and impulsivity. Repetitive behaviours correlated with impulsivity.

Previous research into inhibitory control deficits has produced inconsistent results, and indeed, inhibitory control in this study did not correlate with any component of the ASD triad of impairments. However, a measure of inhibitory control was found to be related to hyperactivity. In contrast, while there was a relationship between autistic symptomatology and theory of mind ability there was no such relationship with behaviours related to ADHD.

Conclusions: Parents reported significant levels of ADHD related behaviours in this group of children with ASD. These behaviours co-occurred with increasing severity of ASD. However, the relationship between cognition and behaviour varies between these traits of ASD and ADHD, suggesting that ASD and ADHD have a degree of shared cognitive underpinning.