Dopamine D2 receptor gene and alcoholism among four aboriginal groups and Han in Taiwan

Previous studies examining the putative association between DRD2 TaqI A1 and alcoholism have produced conflicting results. Major critiques of such studies include potential confounding arising from population admixture by inappropriate selection of controls, failure to screen out substance abusers from controls, and the failure to assess the severity of alcoholics. To address these issues, we compared the allelic frequency of two polymorphisms of DRD2, TaqI A and NcoI, among severe alcoholics and their ethnically matched nonalcoholic controls within four major aboriginal groups and Han (Chinese) in Taiwan. The sample of alcoholics and controls examined for the five groups included 36 and 31 (Atayal), 24 and 23 (Ami), 58 and 58 (Bunun), 35 and 35 (Paiwan), and 50 and 66 (Han). A borderline association between TaqI A1 and alcoholism among the Ami (P = 0.08) and an association between NcoI N1 and alcoholism among Han (P = 0.01) were found. Results of haplotype analysis further confirm that the frequency of haplotype A1N1 was higher in alcoholics than in controls for the Ami (P = 0.01) and Han (P = 0.03). If controls with tobacco abuse were excluded from the analysis, the results remained unchanged. Severity in medical complications of alcohol dependence with withdrawal symptoms was not associated with higher prevalence of DRD2 TaqI A1 or NcoI N1 alleles. The absence of an association between DRD2 and alcoholism among the three aboriginal groups suggests either a higher rate of phenocopies among aboriginal alcoholics or genetic heterogeneity in the susceptibility to alcoholism.