Drug and alcohol use, abuse or dependence are concerns due to the association with high rates of suicide, HIV, homelessness, aggression and incarceration. Moreover, comorbid substance use places additional burden on patients, families, psychiatric services, and government resources due to high rates of treatment non-adherence and relapse. This topic presents the rates of drug and alcohol use in people with schizophrenia spectrum disorders. Please also see the topic on the effects of drug and alcohol use on the course and outcomes of these disorders.

What is the evidence for comorbid drug and alcohol use?

Moderate quality evidence shows the lifetime prevalence of any illicit drug misuse, abuse or dependence in people with schizophrenia ranges between 17% for those in rehabilitation and long-term settings, to 70% in community health settings.

The lifetime prevalence rates of alcohol misuse, abuse or dependence ranges between 29% for those in rehabilitation and long-term settings to 75% in community health settings. Prevalence of alcohol use is higher in studies using the Diagnostic and Statistical Manual of Mental Disorders (DSM) III-revised diagnostic criteria compared to studies using DSM-IV, or the International Classification of Diseases (ICD) 9 or 10. Prevalence is also higher in samples aged 30 to 40 years and in studies published between 1990 and 1995.

The lifetime prevalence of cannabis use disorders in people with schizophrenia is around 27%, with current prevalence around 16%. The prevalence of any cannabis use in first episode psychosis patients is around 33-38%, and around 50% for those at ultra high-risk for psychosis. Prevalence is higher in males and in people under 30 years of age. The initiation of cannabis use is usually around 6-7 years prior to onset of psychosis, and continuation of cannabis use declines after treatment.

The rate of stimulant use disorders in people with psychosis is around 9%. Studies including patients with affective psychosis as well as patients with schizophrenia, studies of inpatients, cannabis users, and studies from USA and Australia report the highest rates of stimulant use.

Any lifetime substance use, particularly cannabis, is associated with an earlier age of onset of psychosis.

March 2022

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Tobacco smoking is very common among people with schizophrenia, who often show particularly heavy usage. This poses considerable health risks, may interfere with antipsychotic medications and may place a financial burden on the individual. Heavy cigarette use may contribute to the increased mortality and reduced life expectancy reported within the schizophrenia population. This topic considers the evidence for the rates of smoking among people with schizophrenia. Please also see the topic on the effects of smoking on the course and outcomes of the disorder.

What is the evidence for smoking?

Moderate quality evidence suggests around 65% of people with schizophrenia have a tobacco use disorder or nicotine dependence, with rates higher in males than females.

Compared with the general population, moderate quality evidence finds higher rates of current smoking, heavy smoking, and lifetime smoking, and lower rates of smoking cessation in people with schizophrenia, with the prevalence of smoking cessation in people with schizophrenia is around 14%.

People with first-episode psychosis, and those at ultra high-risk of psychosis also show higher rates of smoking than the general population, with rates of ~57% and ~33% respectively. There is also a medium-sized increased risk of psychotic disorders, and an earlier age of psychosis onset in smokers compared to non-smokers.

Compared with people with other mental disorders, moderate quality evidence suggests people with schizophrenia show a small to medium-sized effect of higher rates of current smoking, and lower rates of smoking cessation.

March 2022

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