Consistent with alcohol studies, the A118G SNP may better predict treatment outcomes and relapse rates for those attempting to quit smoking rather than predict the susceptibility for developing nicotine dependence. Lerman and colleagues have shown that smokers with the G118 allele are significantly less likely to relapse and report fewer abstinence symptoms than smokers homozygous for the A118 allele (Lerman et al., 2004). A group in the UK reported that female G118 allele-carriers had significantly higher quit rates than female A118 allele-carriers; while the reverse was true for males (Munafo et al., 2007). It should be noted, however, that this study obtained DNA from only 50% of subjects, raising the possibility of ascertainment bias. This evidence supporting the role of the G118 allele in dependence phenotypes, such as liking and craving in chronic smokers, is more robust than evidence for association with the development of nicotine dependence.
