Association analysis between polymorphisms in the dopamine D2 receptor (DRD2) and dopamine transporter (DAT1) genes with cocaine dependence.

Genetic research on cocaine dependence (CD) may help clarify our understanding of the disorder as well as provide novel insights for effective treatment. Since dopamine neurotransmission has been shown to be involved in drug reward, related genes are plausible candidates for susceptibility to CD. The dopamine receptor D(2) (DRD2) protein and dopamine transporter (DAT1) protein play regulatory roles in dopamine neurotransmission. The TaqI A single-nucleotide polymorphism (SNP) in the DRD2 gene and the 3' variable number tandem repeat (VNTR) polymorphism in the DAT1 gene have been implicated in psychiatric disorders and drug addictions. In this study, we hypothesize that these polymorphisms contribute to increased risk for CD. Cocaine-dependent individuals (n=347) and unaffected controls (n=257) of African descent were genotyped for the polymorphisms in the DRD2 and DAT1 genes. We observed no statistically significant differences or trends in allele or genotype frequencies between cases and controls for either of the tested polymorphisms. Our study suggests that there is no association between the DRD2 and DAT1 polymorphisms and CD. However, additional studies using larger sample sizes and clinically homogenous populations are necessary before confidently excluding these variants as contributing genetic risk factors for CD.