Symptoms of ADHD, antisocial behavior, and cognitive performance: A longitudinal twin study.

We investigated longitudinal associations between adolescent attention-deficit/hyperactivity disorder (ADHD) symptoms and later antisocial behavior and tested 1) whether these associations are independent of familial factors shared by co-twins and 2) whether cognitive performance moderates the associations. In a population-based sample of Finnish twins (N = 602-1330, 53% female), we assessed ADHD symptoms with teacher assessments and a diagnostic interview in adolescence, symptoms of antisocial personality disorder with a diagnostic interview in young adulthood, and criminal behavior across the lifespan with self-reports in early midlife. Cognitive performance was assessed with commonly used test measures in young adulthood. Adolescent ADHD symptoms were consistently associated with an increased risk for antisocial symptoms (incidence rate ratio [IRR] = 1.18-1.27) and criminal behavior (IRR = 1.16-1.20) later in life. Within-pair and interaction analyses suggested that the associations were to a large degree independent of familial factors, and cognitive performance level did not moderate them. In conclusion, subclinical ADHD symptoms are associated with an increased risk for antisocial behavior at the population level. The association is not fully explained by familial background, and it is independent of cognitive performance level.