In a large UK population cohort data set of healthy children with higher levels of ADHD symptoms, we had observed that while COMT Val158Met predicted aggression/antisocial behaviour, performance on the available measure of executive function and a questionnaire measure capturing emotion/social cognitive items, the link between genotype and aggression was mediated via the measure of emotional/social cognitive function. This evidence concerns the gene COMT and attention deficit-hyperactivity disorder.