Abstract
The association between the 10‐repeat allele of the dopamine transporter gene (DAT) and attention deficit hyperactivity disorder (ADHD) is uncertain. This study aimed to conduct a meta‐analysis of the association between the 10‐repeat allele of a variable number tandem repeat (VNTR) polymorphism in the 3′‐untranslated region (UTR) of the DAT1 gene and ADHD. We pooled up 18 published transmission disequilibrium test (TDT) studies between the 40‐base pair VNTR polymorphism in the3′‐UTR of the DAT1 gene and ADHD. It included a total of 1,373 informative meioses, 7 haplotype‐based haplotype relative risk (HHRR) studies, and 6 case‐control‐based association studies. There were statistically significant evidences for heterogeneity of the odds ratio in TDT and HHRR studies (P < 0.10), but not in case‐control studies. The results of random effects model showed small but significant association between ADHD and the DAT1 gene in TDT studies (OR = 1.17, 95% CI = 1.05–1.30, chi‐square = 8.11, df = 1, P = 0.004), but not in HHRR and case‐control studies. The 10‐repeat allele of a VNTR polymorphism in the 3′‐UTR the DAT1 gene has a small but significant role in the genetic susceptibility of ADHD. These meta‐analysis findings support the involvement of the dopamine system genes in ADHD liability variation. However, more work is required to further identify the functional allelic variants/mutations that are responsible for this association. © 2006 Wiley‐Liss, Inc.