For SQ, we found seven major haplotypes between SNPs rs16969948 in CHRNA5 and rs6495316 in the intergenic region downstream from the 5′ end of CHRNB4 that showed significant associations. Of these haplotypes, two were positively, and the remaining five were negatively, associated with SI, with a P value ranging from 0.014 for the haplotype CCT, formed by rs481134-rs951266-rs514743, to 0.044 for the haplotype GGA, formed by rs4887077-rs11638372-rs6495316. Although we performed identical association analyses for SC, we found no significant haplotypes in the total sample. By comparing significant haplotypes with SI and SQ, we found four haplotypes, GAA (rs6495308-rs950776-rs11072768), ACT (rs950776-rs11072768-rs7166158), CTC (rs11072768-rs7166158-rs8043123), and GGA (rs4887077-rs11638372-rs6495316), to be significantly associated with both phenotypes under identical genetic models, indicating that they contribute to the etiologies of these two behaviors, likely through a common uncharacterized mechanism.
