We examined the impact of rs2072661 on withdrawal symptoms measured using the withdrawal symptom severity index at TQD, coinciding with the peak symptoms, for those individuals who were abstinent (CO levels <10 ppm) for the week post-TQD. Because bupropion has been shown to impact withdrawal symptoms (26), we stratified our analysis by treatment from a linear regression on all the individuals receiving placebo, there was a 3.8 unit greater magnitude of withdrawal severity for individuals carrying the minor allele compared with those having the WT genotype (P = 0.0009). In contrast, for those who received bupropion, there was only a 0.45 unit difference between the two groups (P = 0.71).
