Nicotine is the addictive chemical in cigarette smoke, and the rate at which a smoker inactivates nicotine, based on CYP2A6 genotype, influences a variety of smoking-behavior phenotypes. These include smoking adoption, smoking status and rate/level, dependence, and cessation. It is conjectured that individuals who carry the genetic predisposition to be faster metabolizers of nicotine would be more prone to develop a dependent smoking habit and would smoke more to maintain nicotine levels in a desired range (i.e., to offset the faster conversion of nicotine to its inactive form, cotinine) (Audrain-McGovern et al., 2007). Further, faster metabolizers may have greater difficulty quitting smoking, due perhaps to increased abstinence symptoms. As described below, each of these hypotheses have received partial support.
