The serotonin transporter gene polymorphism is not associated with smoking behavior

Nicotine increases serotonin release in the brain and symptoms of nicotine withdrawal may be modulated by diminished serotonergic neurotransmission. The promoter region of the serotonin transporter gene, solute carrier family neurotransmitter transporter member 4 (SLC6A4), contains a functional tandem repeat polymorphism. The long (L) variant is more actively transcribed than the short (S) variant and is associated with a higher serotonin uptake. To investigate the potential role of this polymorphism for smoking behavior, SLC6A4 genotypes were determined in two different studies, the SMOKING GENES case-control study (470 current smokers and 419 subjects who had never smoked) and the cross-sectional Ludwigshafen risk and cardiovascular health (LURIC) study (777 current smokers and 1178 subjects who had never smoked). In the SMOKING GENES case-control study, SLC6A4 genotype frequencies were not statistically different between smokers (LL: 30.9%; LS: 46.8%; SS: 16.4%) and non-smokers (LL: 36.3%; LS: 41.8%; SS: 14.3%; P=0.13). Similar results were obtained in the cross-sectional LURIC study (smokers: LL, 36.5%, LS, 45.6%, SS, 17.9%; non-smokers: LL, 33.6%, LS, 48.9%, SS, 17.6%; P=0.33). SLC6A4 genotypes were furthermore not associated with Fagerstrom Tolerance Questionnaire score, packyears, number of cigarettes smoked per day or previous attempts to quit smoking. We conclude that the SLC6A4 promoter polymorphism is not a major determinant of smoking behavior in Caucasian.