Dopamine D-4 gene 7-repeat allele and attention deficit hyperactivity disorder

Objective: Family, twin, and adoption studies show attention deficit hypera ctivity disorder (ADHD) to have a substantial genetic component, and some s tudies have reported an association between ADHD and the dopamine D-4 (DRD4 ) gene. Method: The authors recruited 27 triads that comprised an ADHD adul t, his or her spouse, and their ADHD child. These triads were assessed for ADHD, and their DNA was genotyped for DRD4 alleles. Results: A multiallelic transmission disequilibrium test suggested an association between ADHD and the DRD4 7-repeat allele. Among family members, the number of 7-repeat all eles predicted the diagnosis of ADHD. Conclusions: Prior reports of an asso ciation between ADHD and DRD4 generalize to families recruited through clin ically referred ADHD adults. However, because there are some conflicting st udies, further work is needed to clarify the role of DRD4 in the etiology o f the disorder.