Association between the dopamine D2 receptor A2/A2 genotype and smoking behavior in the Japanese

For the study presented here, we investigated possible links between the dopamine D2 receptor (DRD2) TaqIA genotype (DRD2*A) and smoking behavior in a total of 332 Japanese individuals. For the first time, functional insertion/deletion polymorphism (-141C Ins/Del) in the DRD2 promoter was also examined in relation to smoking behavior. The distribution of the DRD2*A genotype was significantly different among current, former, and never-smokers (P = 0.001; chi(2) test), and smoking appeared to be associated with the DRD2 A2/A2 genotype, showing marked contrast to previous reports for non-Hispanic whites in the United STATES: Multivariate logistic regression analysis incorporating age, sex, genotype, and smoking status as variables revealed that DRD2 A2/A2 genotype was significantly associated with an increased risk of predisposition to smoking behavior in the Japanese (odds ratio, 3.680; 95% confidence interval, 1.499-9.052). In contrast, such an increased risk was not observed in terms of association with the -141C Ins/Del polymorphism. These findings suggest an association of the DRD2*A genotype with an increased risk of being predisposed to smoking behavior in the Japanese and suggest the possible existence of ethnic group-specific differences, which warrant additional studies on the underlying molecular mechanism.