Cases, recruited from ORT clinics in the greater Sydney, Australia, region, were required to be aged 18 years or older, to understand English, and to have participated in ORT for opioid dependence. Participants reporting recent suicidal intent or current psychosis were excluded. Individuals recruited from geographic areas in proximity to ORT clinics, termed neighborhood controls, were excluded for recreational opioid use more than five times lifetime (data were included from 23 controls who denied opioid use more than 5 times at screening but reported greater use with no dependence symptoms at interview); other inclusion and exclusion criteria were identical to those for cases. Institutional review board (IRB) approval was obtained from University of New South Wales (UNSW), Washington University School of Medicine (WUSM), Queensland Institute of Medical Research (QIMR), and area health service ethics committees governing participating clinics. Participants provided written informed consent and were reimbursed AU$50.00 for out-of-pocket expenses.
