The rs3278 is associated reliably with substance abuse vulnerability in (1) a European American sample selected from pedigrees within the Collaborative Study on the Genetics of Alcoholism (COGA; nominal P = 0.03); (2) an African American sample recruited by the National Institute on Drug Abuse (NIDA; nominal P = 0.008); and (3) a NIDA European American sample (P = 0.001).