Cholecystokinin C-45T polymorphism and smoking cessation in women

In view of the effect of cholecystokinin (CCK) on dopaminergic neurons in the mesolimbic "reward" pathway of the brain, its gene has been a focus in studies of dopamine-related conditions and behaviors, including smoking. We assessed the association between the CCK C-45T polymorphism and smoking cessation among women who participated in a randomized clinical trial of d,l-fenfluramine conducted in the Seattle area in 1993-1994. Several years later (Mdn = 3.3 years, range = 2.4-6.9 years), 593 women provided a biological specimen and updated information about smoking habits. We defined short-term quitting as not smoking for at least 7 days immediately preceding the final (12-month) clinical trial visit, and long-term quitting as not smoking for at least the 6-month interval before the later recontact. CCK C-45T was not associated with either short-term (relative risk [RR] associated with the presence of T allele = 0.9, 95% CI = 0.6-1.4) or long-term (RR = 1.0, 95% CI = 0.6-1.5) smoking cessation. Also, we observed no association of this polymorphism with smoking cessation in subgroups of women defined by age or body mass index. No clear differences were found in smoking cessation rates associated with the presence of the T allele among women treated with d,l-fenfluramine versus those randomized to placebo. Our results fail to support prior evidence of an association of the CCK C-45T polymorphism with the ability to quit smoking.