Here we present the results from GWASs of CD and OD related phenotypes measuring the time interval between first use of cocaine or opioids and a DSM-IV dependence diagnosis on the respective drug. These analyses, made possible by the extensive phenotyping performed on three independent cohorts, identified two GWS associations, one specific to AAs and one in the full sample, between relatively common variants and enhanced susceptibility to CD that were not detected at GWS in GWAS that used the bivariate case-control status for dependence as outcomes. Both of these were strengthened after combining meta-analysis with the replication sample. To our knowledge, this is the first time these trait definitions have been studied using GWAS. Although none of the GWS associations in the discovery sample were replicated after correcting for the number of variants tested in the COGA and CATS cohorts, 13 (9%) of the CD TD SNPs and 11 (5.5%) of the OD TD SNPs were nominally significant in one of those samples with the same effect direction.
