A novel genome-wide significant association was observed on chromosome 20q13 (lowest P=3.8 × 10−8 for rs4809294, Figure 1a). In total, 23 SNPs/indels on chromosome 20q13 were associated at P<5 × 10−5 (Supplementary Table 1). We also observed associations within the known gene clusters on chromosomes 15q25 (CHRNA5-CHRNA3-CHRNB4, lowest P=3.5 × 10−17) and 8p11 (CHRNB3-CHRNA6, lowest P=1.2 × 10−6) (Figure 1a and Supplementary Tables 2 and 3). None of the 23 top-associated CHRNA4 SNPs interacted with previously established SNPs in the known regions (Supplementary Table 4).
