A study on dopaminergic and serotonergic genes that have a role in smoking addiction at the DNA level

Aim: To investigate DRD2 (TaqIA and -141C Ins/Del), DAT (40-bp VNTR) and MAO-A (uVNTR) gene variants which have a role in dopaminergic and serotonergic systems within the frame of comparing them in smoker and non-smoker individuals; as well as to investigate them in case of clinical parameters such as their effects on age of starting to smoke, average number of cigarettes smoked each day and Fagerstrom Test for Nicotine Dependence score. Methods: 164 smoker (90 male, 74 female) and 124 non-smoker (58 male, 66 female) individuals included in the study. Variants were analyzed by PCR or the PCR-RFLP method. Results were compared between groups and with clinical parameters. Results: DRD2/-141C Ins/Del variant was found to be associated with smoking addiction (p<0.001) and clinical parameters (p=0.037), whereas MAO-A/uVNTR variant was associated with smoking addiction solely in male (p=0.003). No significant association was found in relation to smoking addiction and clinical parameters in DRD2/TaqIA and DAT/40 bp VNTR variants. Conclusion: It was shown that DRD2 Del/Del genotype, MAO-A 4R allele presence in males may contribute to the risk of smoking addiction; that DRD2 Ins/Ins genotype, MAO-A 3.5R alleles in males may be linked to a protective effect. DRD2 Ins/Del genotype was found to be associated with less smoking per day.