Evidence suggesting the role of specific genetic factors in cigarette smoking

Twin studies suggest that propensity to smoke and ability to quit smoking a re influenced by genetic factors. As a means of investigating the risk of s moking associated with genetic polymorphisms in the dopamine transporter (S LC6A3) and the D-2 dopamine receptor (DRD2) genes, a case-control study of 289 smokers and 233 nonsmoking controls and a case series analysis of smoke rs were conducted. A significant effect for SLC6A3 and a significant gene-g ene interaction were found in a logistic regression model, indicating that individuals with SLC6A3-9 genotypes were significantly less likely to be sm okers, especially if they also had DRD2-A2 genotypes. Smokers with SLC6A3-9 genotypes were also significantly less likely to have started smoking befo re 16 years of age and had prior smoking histories indicating a longer peri od of prior smoking cessation. This study provides preliminary evidence tha t the SLC6A3 gene may influence smoking initiation and nicotine dependence.