Several genes found unequivocally associated with nicotine addiction and treatment, namely, CHRNA3, CHRNB4, CHRNA5, NRXN1, and CYP2A6 (Nussbaum et al., 2008; Wassenaar et al., 2011; Broms et al., 2012; Chen et al., 2014; Zhu et al., 2014; Pérez-Rubio et al., 2016). The gene discussed is CYP2A6; the disease is nicotine dependence.