Substance use among patients in specialized mental health services in Norway: prevalence and patient characteristics based on a national census

Purpose: The aim of this study was to investigate the clinical and demographic variation in the prevalence of substance use among the general psychiatric population in Norway.

Methods: A national census in psychiatric institutions and outpatient clinics was conducted. Data were returned for 2358 inpatients (response rate, 65%) and 23,167 outpatients (response rate, 60%). Substance use was measured based on substance use disorder diagnosis or reported substance use in the last 4 weeks (alcohol 2-4 days a week or more frequently/illicit drug use). Regression analyses controlling for demographic and sociodemographic characteristics were carried out.

Results: Substance use was identified in 32.4% of inpatients and 13.9% of outpatients. The most frequently reported substances used were alcohol, sedatives and cannabis. Among inpatients, the prevalence of substance use was highest in patients with schizophrenia, personality disorders and anxiety disorders. Among outpatients, the prevalence was highest in patients with schizophrenia and other psychoses. Inpatients with anxiety disorders and outpatients with schizophrenia and other psychoses had a significantly higher risk of substance use than other patients. In both samples, the prevalence of substance use was higher among males, 24 to 29-year-olds and the most socially deprived.

Conclusions: This study provides further knowledge about patients at risk for co-morbid substance abuse and poor treatment outcomes. Clinicians may consider targeting patients with schizophrenia and other psychoses, young males and those who are socially deprived in efforts to prevent emerging substance abuse and improve outcomes.