Variation in an independent group of nicotinic receptors is also associated with the development of heavy smoking and nicotine dependence. The nicotinic receptor gene cluster on chromosome 8 that includes the α6 and β3 nicotinic receptor subunit gene cluster (CHRNA6, CHRNB3) is correlated with smoking behavior. This region generated genome-wide significant association with nicotine dependence, though the strength of this association is much less (rs6474412 p=1.4 × 10−8) (Thorgeirsson et al., 2010).
