Association Between Dopamine Receptor 2 TaqIA Polymorphisms and Smoking Behavior With an Influence of Ethnicity: A Systematic Review and Meta-Analysis Update

The relationship between dopamine receptor D2 (DRD2) gene TaqIA polymorphisms and smoking behavior remains controversial. The aim of this review was to update a previous meta-analysis on the effect of DRD2 polymorphisms on smoking behavior by considering the influence of ethnicity. This review presents analyses stratified by ancestry, as the samples included individuals of different ethnicities. Pooled effect sizes were calculated using fixed- and random-effects models to verify heterogeneity. We investigated the association for the proportion of men and Caucasians by regression analysis using the effect sizes calculated by each meta-analysis. Analysis of smoking cessation revealed a significant effect, which suggested that ethnic differences between Caucasians and Asians moderate the effect of DRD2 polymorphisms. Smoking initiation and rate exhibited no relationship with DRD2 polymorphisms; furthermore, we detected heterogeneity. Although the analysis of smoking persistence indicated significant effects, heterogeneity was detected. The finding of heterogeneity for smoking persistence and rate suggests the possibility of genegene interactions arising from ethnic differences between the samples. We found a significant inverse relationship between the proportion of men and effect sizes among Caucasians for smoking persistence and rate. Gender differences between Caucasian samples may moderate the effect of DRD2 polymorphisms on smoking persistence and rate. Our findings indicate that the ethnicity of the participants alters the effect of DRD2 polymorphisms on smoking behavior. The observed heterogeneity may be associated with participant gender as a moderating factor, and the association may be specific to Caucasians.