Epidemiology of psychiatric disorders in Edmonton. Drug abuse and dependence

3258 randomly selected adult household residents of Edmonton were interviewed by trained lay interviewers using the Diagnostic Interview Schedule (DIS). The lifetime prevalence of drug abuse/dependence was 6.9%, with a male:female ratio of 3:1. The most commonly used drug was cannabis followed by amphetamines, opiates, barbiturates, hallucinogens and cocaine. 80.3% of those with drug abuse/dependence also had a lifetime diagnosis of another psychiatric disorder. In those with a comorbid diagnosis, the mean age of onset for the other psychiatric disorder was generally found to be younger than for the onset of drug abuse/dependence. Different comorbid disorders were found to significantly affect patterns of drug use.