Nicotine dependence is a leading predictor of smoking continuation (Breslau et al., 2001; Johnson et al., 2002). Thus an improved understanding of the biological underpinnings of nicotine dependence may be key to the success of further smoking cessation efforts. Twin studies find significant genetic influences on nicotine dependence (Lessov et al., 2004; Maes et al., 2004; Pergadia et al., 2006; Prescott and Kendler, 1995), motivating the search for genetic variants that influence risk for nicotine dependence.
