Prevalence of psychosis/substance abuse comorbidity - Clinical epidemiological findings from different treatment settings in a large German city

Comorbid substance use disorders in schizophrenia are of high clinical relevance, because they are common and they are mostly associated with an unfavourable long-term prognosis. Whereas the clinical impression suggests a continuous increase of substance use disorders in patients with schizophrenia over the last 10-20 years, results from epidemiological studies have been inconsistent. The aim of the present investigation was to study the prevalence of substance use disorders within a large sample of patients with schizophrenia in a large German city (Cologne). The prevalence data were examined in different treatment settings (outpatient vs inpatient, university hospital vs mental health hospital). Risk factors for substance use disorders and preferences for specific substances were analysed. The lifetime prevalence of comorbid substance use disorders in the entire sample of 2,337 patients with schizophrenia was 29.4%. However, the data varied substantially depending on the setting of treatment, with the highest comorbidity rates being prevalent in the inpatient sample. Alcohol and cannabis were the most commonly used substances. Commonly recognized risk factors for substance use disorders, such as being male and unmarried and having a low education level, were replicated.