Genomic DNAs came from NIH IRP (NIDA) research volunteers of self-reported European and African–American descent whose drug use and dependence were characterized as described (Liu et al., 2005a,b; Uhl et al., 2001). A total of 389 unrelated European-American “abusers,” averaged 35 years of age, scored 3+ on a total drug use scale of drug use of addictive substances, and demonstrated DSMIII-R or DSMIV dependence on at least one illegal abused substance. Two hundred forty “control” European-Americans with average age of 32 years reported no significant lifetime histories of use of any addictive substance and 0–1+ DUS (drug use scale) total drug use scores. DNAs from “abusers” of self-reported African–American descent numbered two hundred forty in total, while one hundred “control” African-Americans were analyzed for the current study.
