Genetic predisposition in alcoholism: association of the D2 dopamine receptor TaqI B1 RFLP with severe alcoholics.

Previous studies have shown an association of the 3' Taq1 A1 allele of the D2 dopamine receptor (DRD2) gene with severe alcoholism. The recent demonstration of a new polymorphism located closer to the regulatory regions of this gene, permits an associational analysis of these 5' Taq1 B alleles with alcoholism and a comparison with the 3' Taq1 A alleles. Restriction fragment length polymorphism methodology was used to analyze a total of 133 blood samples of nonalcoholics, less severe alcoholics, and severe alcoholics. In white subjects (n = 115), no significant difference in the prevalence of the B1 allele is found between nonalcoholics (n = 30) and less severe alcoholics (n = 36). However, the prevalence of this allele is significantly higher in severe alcoholics (n = 49) when compared to either nonalcoholics (p = 0.008) or less severe alcoholics (p = 0.005). When Taq1 B and Taq1 A alleles of the DRD2 gene are compared in whites, the prevalence of the A1 allele is significantly higher than the B1 allele only in the severe alcoholic group. In conclusion, alleles in both the 5' and 3' region of the DRD2 gene associate with severe alcoholism. This suggests that the DRD2 gene may have an etiological role in some severe alcoholics.