At first, RVs in different genes were analyzed separately. Based on the power analysis of the association tests, the power to detect RVs with relative risk of 2 for AD, CD and OD was 55%, 47% and 60% in AAs; 52%, 58% and 65% in EAs (Figure S2A and S2B). We observed that in AAs, DISC1 and GRIN2B were significantly associated with OD (P=0.0010 and 0.00085, respectively) (Table 3). Both were highly significance based on Bonferroni correction (P=0.0012). No statistically significant associations were observed in EAs. Three RVs in DISC1 were investigated in this study. In AAs, differences in MAF between opioid dependence cases and controls at two stages are very similar (Table 3). In the combined sample, the minor allele of the first RV, rs139667828, was observed in 64 of the 6386 chromosomes (1.00%) in OD controls, and 5 of the 1832 chromosomes (0.27%) in OD cases; the minor allele of the second RV rs116628628 occurred in 26 of the 6334 chromosomes (0.41%) in OD controls, and 13 of the 1838 chromosomes (0.71%) in OD cases; the minor allele
