The sample for these genetic analyses consisted of 224 pedigrees (N=520 individuals) with complete nicotine withdrawal data, where 158 pedigrees had linkage scan genotype data and 172 pedigrees had OPRM1 SNP data. The sample of SMOFAM subjects with complete OPRM1 genotype and nicotine withdrawal sensitivity scores (N=419) used in these analyses was approximately equally divided by gender and by smoking status (current versus former smokers with a small proportion of experimenters) (Table 1). In these analyses 45% of subjects stated that they had relapsed due to withdrawal symptoms (data not shown). In the sample of 520 subjects, the nicotine withdrawal sensitivity score distribution is approximately normal (Figure 1), and has a mean value of −0.014 with a standard deviation of 1.84. An increased risk of relapse was associated with the nicotine withdrawal sensitivity score (OR=1.25, 95%CI=1.10,1.42) (data not shown). Models testing for associations between gender and the nicotine withdrawal sensitivity score were null and therefore adjustments for gender were considered unnecessary in these analyses.
