Analysis of baseline smoking behavior among all genotyped subjects, as measured by the number of CPD, revealed a genetic association with the primary nicotine dependence locus on chromosome 15q25, indicating that the population studied here is consistent with previous populations evaluated for nicotine dependence (Thorgeirsson et al, 2008). The most significant SNP detected in this region was rs4275821 (p<0.003), although we also detected nominal associations with other SNPs, including rs16969968 (p<0.03). The CPD association with the 15q25 region was detected in this population despite the absence of a full range of smoking phenotypes (individuals smoking <10 CPD were excluded from the clinical trials) (Gonzales et al, 2006; Jorenby et al, 2006; Oncken et al, 2006). We also detected an association between the 15q25 locus and scores from the Fagerström Test for Nicotine Dependence (p<0.004, rs12443170).
