Our GWAS discovery samples (‘GCD sample’) included 2379 EA and 3318 AA subjects. A second identically ascertained GCD sample comprising 1746 EA and 803 AA subjects was used for replication. All subjects were recruited for studies of the genetics of drug (opioid or cocaine) or alcohol dependence.1,2 The sample consisted of small nuclear families (SNFs) originally collected for linkage studies and unrelated individuals. Subjects (Table 1) gave written informed consent as approved by the institutional review board at each site, and certificates of confidentiality were obtained from NIDA and NIAAA. Subjects were administered the semi-structured assessment for drug dependence and alcoholism (SSADDA)16 to derive DSM-IV diagnoses17 of lifetime AD and other major psychiatric traits.
