Cases were recruited from clinics providing opioid replacement therapy (ORT) in the greater Sydney region. Prior to enrollment in ORT, NSW guidelines require an extensive clinical assessment documenting that the individual meets DSM-IV diagnostic criteria for opioid dependence and is suitable for the form of maintenance treatment recommended. For cases, inclusion criteria were age 18 years or older, an adequate understanding of English, and current or past participation in ORT consisting of either methadone or buprenorphine for heroin dependence. Participants reporting recent suicidal intent or known to be currently experiencing psychosis were excluded. Neighborhood controls were recruited from geographic areas in proximity to ORT clinics. The use of opioids recreationally more than ten times lifetime was an exclusion criterion for controls; the inclusion and exclusion criteria except for ORT participation were otherwise identical to cases. Written informed consent was obtained from all participants. Institutional review board (IRB) approval was obtained from the University of New South Wales, Washington University, the Queensland Institute of Medical Research, and the area health service ethics committees governing the participating clinics. Participants were reimbursed AU$50.00 for out-of-pocket expenses.
