Quantile-quantile plots of the −log10 p-values for SNP association with smoking behaviors (Figure S1) showed no evidence for systematic bias (each genomic inflation factor λ<1.02). None of the SNPs achieved genome-wide significance (p<10−7) in any combined analysis pooling evidence for association across the two studies (Figures 1 and 2). Table 2 lists detailed results for SNPs with a combined-analysis p-value<10−5 for each smoking behavior. For the combined GWAS analysis of the seven smoking behaviors, the most significant SNP smoking behavior association result is rs6437740 with CPD (P = 2.4×10−7). Including this result, there are 8 gene regions and 3 genomic regions with predicted but not verified coding regions associated with SNPs in the group of SNP smoking behavior results with P<10−5 (Table 2). We observed no evidence for systematic heterogeneity in results between studies, and no single SNP showed evidence for heterogeneity by sex at the genome-wide significance level (see summary of Q statistics in Figure S2).
