Genetic Epidemiology of Attention Deficit Hyperactivity Disorder (ADHD Index) in Adults

CONTEXT In contrast to the large number of studies in children, there is little information on the contribution of genetic factors to Attention Deficit Hyperactivity Disorder (ADHD) in adults. OBJECTIVE To estimate the heritability of ADHD in adults as assessed by the ADHD index scored from the CAARS (Conners' Adult ADHD Rating Scales). DESIGN Phenotype data from over 12,000 adults (twins, siblings and parents) registered with the Netherlands Twin Register were analyzed using genetic structural equation modeling. MAIN OUTCOME MEASURES Heritability estimates for ADHD from the twin-family study. RESULTS Heritability of ADHD in adults is estimated around 30% in men and women. There is some evidence for assortative mating. All familial transmission is explained by genetic inheritance, there is no support for the hypothesis that cultural transmission from parents to offspring is important. CONCLUSION Heritability for ADHD features in adults is present, but is substantially lower than it is in children.