Effects of Interaction Between Dopamine D2 Receptor and Monoamine Oxidase A Genes on Smoking Status in Young Men

Although the effect of gene–gene interaction on nicotine–dopamine metabolism for smoking behavior has been reported, polymorphisms of dopamine D2 receptor (DRD2) and monoamine oxidase A (MAOA) have not been simultaneously examined among smokers. In this study, 481 young Taiwanese men completed a self-report questionnaire on smoking status, and data were obtained on polymorphisms of DRD2 rs1800497, DRD2 rs1079597, MAOA rs309850, and MAOA rs1137070, urinary nicotine, and urinary cotinine. In a comparison of 261 current smokers and 220 never smokers, odds ratios (ORs) for the development of smoking in all genotypes were not statistically significant. Among smokers with DRD2 rs1079597 GG//MAOA rs309850 3-repeat, the OR of heavier smoking was 2.67 times higher (95% confidence interval [CI]: [1.08, 6.59], p = .031) and the score on the Fagerstrom test for nicotine dependence was higher (4.26 vs. 2.83) than in those with DRD2 rs1079597 AA//MAOA rs309850 3-repeat. Adjusted urinary cotinine concentration was significantly different between those two groups (median value: 95.83 ng/μl vs. 133.24 ng/μl, respectively, p = .045). These findings suggest that the interaction of DRD2 rs1079597 and MAOA rs309850 3-repeat affects smoking intensity in young Taiwanese men.