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Cannabis use and psychosis
1National Drug and Alcohol Research Centre, University of New South Wales, Sydney, 2052, Australia.
Drug and Alcohol Review
|October 6, 2005
Summary
Cannabis use may be linked to psychosis, with evidence suggesting it can precipitate schizophrenia or worsen its symptoms. Heavy, prolonged use of potent cannabis may rarely cause a distinct "cannabis psychosis." Further research is needed to clarify causal links.
Area of Science:
- Psychiatry
- Neuroscience
- Addiction Medicine
Background:
- Cannabis use is prevalent globally.
- The relationship between cannabis and psychosis is complex and debated.
- Two main hypotheses exist: cannabis-induced psychosis and cannabis as a risk factor for schizophrenia.
Purpose of the Study:
- To review and evaluate the evidence supporting two hypotheses on cannabis use and psychosis.
- To examine the potential causal link between cannabis use and schizophrenia.
- To assess the impact of cannabis on schizophrenia symptom exacerbation.
Main Methods:
- Review of existing clinical and epidemiological evidence.
- Analysis of prospective studies examining cannabis use and schizophrenia diagnosis.
- Assessment of confounding factors such as other substance use and pre-existing vulnerabilities.
Main Results:
- Limited clinical support for a rare
- cannabis psychosis
- requiring high THC doses or potent forms.
- Stronger evidence suggests a linear relationship between adolescent cannabis use frequency and later schizophrenia risk.
- Cannabis use is more clearly linked to exacerbating existing schizophrenia symptoms.
Conclusions:
- Cannabis use may precipitate schizophrenia, though causality and mechanisms (e.g., self-medication, other drug use) require further investigation.
- Cannabis use is strongly associated with worsening schizophrenia symptoms.
- Mental health services should counsel schizophrenia patients on reducing or abstaining from cannabis and other substance use.