Two hundred and fifty control subjects and 325 former severe heroin addicts, who were consecutive volunteers in genetic studies in our laboratory at The Rockefeller University and who met the inclusion criteria defined below were included in this study. They were recruited from advertisements and from clinical resources in New York City. An informed consent approved by The Rockefeller University Hospital Institutional Review Board that gave specific consent for genetic studies was signed by all subjects. Based on the ethnic/cultural background of the subjects, their parents, grandparents, and great-grandparents, subjects were classified as Caucasian (n = 350) or African American (n = 225).
