Three hundred and sixty nine subjects participated in the study (202 cases and 167 controls). There were 54% percent females in the control group and 38% in the case group. The mean age at recruitment was 31.9 (±11.7) years in the control group and 47.0 (±8.8) years in the case group. The patients (cases) were former severe heroin addicts from methadone maintenance treatment programs. Subjects were recruited at the Rockefeller University Hospital, the Manhattan Campus of the VA NY Harbor Health Care System, Weill Medical College of Cornell University, and the Dr. Miriam and Sheldon G. Adelson Clinic for Drug Abuse Treatment and Research, Las Vegas. Ascertainment was made by personal interview, using several instruments: the Addiction Severity Index (ASI) (Mclellan et al., 1992), the Kreek-McHugh-Schluger-Kellogg scale (KMSK) (Kellogg et al., 2003), and the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV). All subjects had a history of using heroin multiple times per day, every day for at least one year. The 167 control subjects were recruited at the Rockefeller University Hospital. Each of the following was used
