To further understand the interplay between the haplotypes and treatment, we added cigarettes per day (CPD) and the interaction between CPD and treatment to determine if the relationship between the haplotype status and abstinence depended upon smoking heaviness (as a measure of dependence). Heavier smoking was associated with less abstinence (OR=0.67, 95% CI=0.60-0.75, p=2.8×10−11), but this relationship did not differ by treatment status (X2=0.98, df=1, omnibus-p=0.32 for the interaction). The interaction between the haplotypes and treatment remained significant (X2=8.61, df=2, omnibus-p=0.013 for the interaction; Table S3), after adjusting for CPD.
