any other ANKK1, TTC12, or DRD2 SNP. Since prior studies6,11,49–53 that reported an association of rs1800497 with opioid dependence genotyped few or no additional ANKK1 SNPs, the signal they observed may have resulted from similar LD. The only association not attributable to LD in our sample involved rs4492854, an NCAM1 SNP, for which risk was best explained by a dominant model. Owing to the complete lack of LD between rs877138 and rs4492854, we instead examined risk associated with these SNPs in tandem rather than the haplotype-based analyses used in prior investigations38,40,42,44 and found greater than 4-fold variation in risk (OR = 4.30; 95%CI, 2.36–7.84) across combinations of these two SNPs.
