The CHRNA5-CHRNA3-CHRNB4 variants have been less consistently associated with cessation outcomes than with smoking heaviness measures. Five studies show an association between the CHRNA5-CHRNA3-CHRNB4 region and successful smoking cessation (16-20). All five found that the same genetic risk variants that contribute to smoking heaviness and nicotine dependence also predicted smoking cessation. Other studies, however, fail to confirm this association (21-23). A genome-wide association of three treatment cohorts did not identify any nicotinic receptor genes as predictors of prospectively-measured smoking cessation (23). One large genome-wide association meta-analysis that strongly supported the association between 15q25.1 and smoking heaviness failed to find an association with current versus former smoking as a measure of smoking cessation at a genome wide level of significance (10).
