Table 1 shows that a large portion of our heroin addiction cases also reported abuse (using 10 or more times in the past month) of other drugs, predominantly cocaine. We repeated the haplotype association analyses for heroin addiction after excluding the cases with comorbid cocaine abuse, leaving 490 EA cases and 703 AA cases for comparison to the population control sets. With this reduced sample, the rs1344706-A/rs7597593-T haplotype remained associated in the European Americans (P=0.014, odds ratio [95% confidence interval] = 1.21 [1.04–1.41]); its multiancestry meta-analysis had P=0.065 and a similar magnitude of association (odds ratio [95% confidence interval] = 1.12 [0.9–1.27]) in comparison to the full sample (Table 3).
