The inactive form of aldehyde dehydrogenase-2 (ALDH2) is regarded as a protective factor against the development of alcoholism, and alcoholics with inactive ALDH2 are considered to be relatively homogeneous. This examination of a possible allelic association of the dopamine D2 receptor (DRD2) gene TaqI A polymorphism failed to detect significant differences between 583 Japanese alcoholics and 295 unrelated Japanese controls, or between alcoholic subjects with different ALDH2 genotypes. Despite the significantly higher frequency of the DRD2 A1 allele in the 207 alcoholics with inactive ALDH2 than in the 376 alcoholics with active ALDH2, multiple logistic regression analysis (controlled for the ALDH2 genotype) revealed no association between the TaqI A polymorphism and alcoholism. Nor did the frequency of the DRD2 TaqI A polymorphism differ in alcoholic subjects grouped by several pertinent clinical characteristics, including severity of alcoholism. Although there remains a possibility that the DRD2 TaqI A polymorphism plays some role in modifying the phenotype of the disease, these results suggest that neither the A1 allele nor the homozygous A1 genotype is associated with alcoholism.
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