Objective: Prevalence estimates of illicit drug use in psychotic disorders vary between studies, and only a few studies compared prevalence estimates with those in the general population.
Method: Cross-sectional study comparing 148 stable-phase patients with schizophrenia or bipolar disorder with 329 representative general citizens of Oslo. A total of 849 patients from the same hospital department in the same time period constituted a patient reference group.
Results: Lifetime illicit drug use was 44% higher (P < 0.001) in study patients than in the general population sample; while lifetime use of amphetamine/cocaine was 160% higher (P < 0.001). No differences were found between user groups for sociodemographic characteristics.
Conclusion: Patients with psychotic disorders in stable phase had a markedly higher lifetime use of any illicit substance, especially amphetamine/cocaine, than the general population. They also seemed to use drugs more periodically. The same sociodemographic characteristics were associated with increased illicit drug use in both groups.