Our sample consisted of 194 former severe heroin addicts and 135 control subjects (N = 329), all of Caucasian ethnicity, drawn from consecutive volunteers (January 1995 – June 2007) in genetic studies conducted by the Laboratory of the Biology of Addictive Diseases at The Rockefeller University who met the inclusion criteria defined below (Table 1). Subjects were recruited from clinical resources in New York City, and from referrals, newspaper advertisements, and posted notices. All subjects gave specific consent for genetic studies and signed an informed consent approved by The Rockefeller University Hospital Institutional Review Board. Ethnicity was based on the ethnic/cultural background of the subjects, their parents, grandparents, and great-grandparents.
