Patterns of lifetime drug use among intravenous drug users.

To obtain a clearer description of the natural history of intravenous drug use (IVDU), 92 intravenous drug users (IVDUs), not selected through treatment or contact with the legal system, were identified. Concerning lifetime use, central nervous system (CNS) stimulants were the most common class of drug to be injected (by 72.8% of IVDUs), followed by opiates (by 50.0% of IVDUs). Mean age of onset of IVDU in this sample was 18.5 years, following initiation of alcohol use by an average of 4.6 years and cannabis use by an average of 2.1 years. Any history of IVDU in this sample indicated substantial lifetime use of illicit drugs and early onset of psychoactive substance use.