Association study of DRD2 and MAOA genes with subtyped alcoholism comorbid with bipolar disorder in Han Chinese

Background: Several studies have hypothesized that genes involved in the dopamine system, including dopamine type-2 receptor (DRD2)-related TaqIA polymorphism and monoamine oxidase-A upstream variable number tandem repeat (uVNTR), may be associated with alcoholism. But their results were contradictory because of alcoholism's heterogeneity. Therefore, we examined whether the DRD2TaqIA and MAOA-uVNTR gene polymorphisms are susceptibility factors for alcoholism comorbid with bipolar disorder (ALC. +. BP) in Han Chinese in Taiwan. Methods: We recruited 101 Han Chinese men with comorbid alcoholism and bipolar disorder, and 328 healthy male controls from the community. Genotyping was done using PCR-RFLP. Results: There were no significant differences in the genotypic frequencies of the DRD2TaqIA or the MAOA-uVNTR polymorphisms between the 2 groups. The MAOA-uVNTR 3-repeat had a significant protective effect on the ALC. +. BP (odds ratio = 0.432, p= 0.035) but not on the healthy controls. However, the interaction between the MAOA-uVNTR 3-repeat and DRD2 A1/A2 was a risk factor in the ALC. +. BP (odds ratio = 3.451, p= 0.018). Conclusions: We indicated the impact of the association between MAOA-uVNTR 3-repeat and DRD2 A1/A2 with ALC. +. BP.