Dopamine system genes and attention deficit hyperactivity disorder: a meta-analysis

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Abstract
The dopamine system may play a major role in the development of attention deficit hyperactivity disorder (ADHD). We applied a random-effects model meta-analysis to family-based studies of association between ADHD and the dopamine system genes DRD4, DRD5 and DAT1. A statistical test of heterogeneity was conducted for each group of studies. The meta-analysis of DRD4 included data from 13 studies, with a total of 571 informative meioses. The pooled odds ratio estimate was 1.41 (95% CI 1.20–1.64, P=1.57×10−5), demonstrating positive association. For DRD5, data from five studies, with a total of 340 informative meioses, were combined yielding a pooled odds ratio of 1.57 (95% CI 1.25–1.96, P=8.28×10−5). Eleven studies examining DAT1, with a total of 824 informative meioses, yielded a non-significant pooled odds ratio estimate of 1.27 (95% CI 0.99–1.63, P=0.06). There was no support of heterogeneity between the studies. Overall, the meta-analyses support the involvement of the dopamine system genes in ADHD liability variation and suggest the need for studies examining interactions between these genes.