CHRNA5-CHRNA3-CHRNB4 haplotypes with tolerance, craving, and loss of control, but only among individuals who began smoking early in life, suggesting that the genetic risk may only occur with early tobacco exposure (Baker et al. 2009). The CHRNA5-CHRNA3-CHRNB4 haplotypes are also associated with withdrawal severity and inability to stop smoking, but there was no interaction with age at daily smoking for these phenotypes (Baker et al. 2009). Another study by Sarginson and colleagues identified CHRNA5 SNP rs680244 and CHRNB4 SNP rs12914008 as predictors of 7-day point-prevalence at 52-week follow-up in Caucasians and the CHRNA3 SNP rs8192475 as a predictor of craving after quitting and withdrawal symptoms over 42 days (Sarginson et al. 2011). More recently, Munafo and colleagues found a weak association between the rs1051730 polymorphism and decreased likelihood of smoking cessation at follow-up after 4 weeks of open-label nicotine transdermal patch treatment, but not in a second placebo-controlled clinical trial (Munafo et al. 2011). Recent data from King and colleagues show an association of CHRNA5 SNP rs518425 with abstinence in smokers treated with the α4β2* partial agonist varenicline in a large pharmacogenetic trial (King et al. 2011).
