A meta‐analysis of association studies between the 10‐repeat allele of a VNTR polymorphism in the 3′‐UTR of dopamine transporter gene and attention deficit hyperactivity disorder

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.