In the AA GWAS, all drugs contributed to the chromosome 3 GWS signal, albeit at nominal levels of significance, while all drugs except opioids and sedatives contributed to the chromosome 5 and 13 signals (Table 3). Alcohol dependence was also associated with these loci (Table 3); however, when a smaller subset of individuals who met criteria for drug but not alcohol dependence was studied (i.e., drug_noalc), the loci on chromosome 3, 5 and 13 remained nominally associated (all p<5.04×10–4; Table 4), suggesting that these signals were only partially attributable to shared genetic liability between alcohol and illicit drug dependence. In contrast, the trans-ancestral signal on chromosome 1 was due primarily to association with cocaine and alcohol dependence in both the EA and AA subsamples (Table 3). When individuals with alcohol dependence only were excluded from the study (drug_noalc), there was no association (p=0.42) in the EAs and the association in AAs decreased in significance to p=0.04.
