Consistent with this prior work, we detected a significant association of rs2236196 with a quantitative trait (CPD) in the combined sample, as well as in AAs and EAs. Specifically, we found that the rs2236196 “G” allele was associated with higher number of CPD, a finding consistent in magnitude and direction with the findings from previous studies (Hutchison et al., 2007; Saccone et al., 2007; Breitling et al., 2009). Although the association between rs2236196 and CPD in the combined sample did not survive multiple testing (Pcorrected = 0.075), given the prior findings of association between rs2236196 and smoking behavior, a nominally significant p-value could be considered of interest, which would provide evidence of replication of the finding that rs2236196 plays a role in smoking behavior. However, no significant evidence was observed for association between rs2236196 and the two binary traits of ND or dichotomized FTND. Because the SSADDA does not include an assessment of the maximum number of cigarettes smoked in a 24-hour period (the trait that we identified through the linkage signal with CHRNA4 in the meta-analysis), we cannot directly test the association of CHRNA4 variants with this phenotype.
