Objective: To clarify the nature of the association between dopamine genes and smoking by examining whether genetic variability in components of the dopamine pathway could explain refined phenotypes in adolescent smoking progression.
Method: Data are from an ongoing prospective study of the long-term outcome of early risk factors studied since birth. At age 15 years, 220 participants (108 males, 112 females) completed a self-report questionnaire measuring smoking behavior and were genotyped for five dopamine gene variants.
Results: Smoking initiation was related to allelic variation in the dopamine D4 receptor gene (DRD4), whereas smoking continuation and dependence showed association with the dopamine D2 receptor gene (DRD2). Adolescents with the seven-repeat allele of the common DRD4 exon 3 polymorphism had rates of ever smoking that were significantly higher than in those with other genotypes. Once smoking started, carriers of the T allele of a single nucleotide polymorphism of DRD2 (rs4648317) reported higher rates of current smoking and scored higher on nicotine dependence than their allelic counterparts. Among current smokers, intention to quit was significantly lower in adolescents homozygous for the 10-repeat allele of the common dopamine transporter 3' untranslated region polymorphism.
Conclusions: Our results provide preliminary evidence of genetic influences on different stages of smoking and suggest the importance of specific dopamine genes in smoking progression in adolescence.