Meta-analysis of the association between the 7-repeat allele of the dopamine D-4 receptor gene and attention deficit hyperactivity disorder

Objective: Family, twin, and adoption studies show attention deficit hypera ctivity disorder (ADHD) to have a substantial genetic component. Although s everal studies have shown an association between ADHD and the 7-repeat alle le of the dopamine Dq receptor gene (DRD4), several studies have not. Thus, the status of the ADHD-DRD4 association is uncertain. Method: Meta-analysis was applied to case-control and family-based studies of the association between ADHD and DRD4 to assess the joint evidence for t he association, the influence of individual studies, and evidence for publi cation bias. Results: For both the case-control and family-based studies, the authors fo und 1) support for the association between ADHD and DRD4, 2) no evidence th at this association was accounted for by any one study, and 3) no evidence for publication bias. Conclusions: Although the association between ADHD and DRD4 is small, these results suggest that it is real. Further studies are needed to clarify wha t variant of DRD4 (or some nearby gene) accounts for this association.