Alternatively, this genetic signal, although more proximate to CYP2B6, may have a more direct effect on the adjacent CYP2A6 locus, which is itself associated with continuous abstinence from weeks 9 to 52. In addition to (or perhaps because of) its role in nicotine metabolism, the CYP2A6 locus has also recently been found to be genetically associated with nicotine dependence (The Tobacco and Genetics Consortium, 2010; Thorgeirsson et al, 2010), and phenotypic markers of nicotine metabolism rate have reproducible associations with prospective smoking cessation (Ray et al, 2009). Continuous abstinence from weeks 9 to 52 also showed weaker associations with HTR3B and CHRNA10 in the entire cohort. The association with HTR3B may be explained relative to its association with relapse to smoking (described below). The potential role of CHRN10A in smoking cessation is less clear, although it has been shown recently to be associated with nicotine dependence in an African-American population (Saccone et al, 2010a, 2010b).
