Cannabis Exacerbates Schizophrenia Symptoms and Prolongs Recovery Interview with:
Ian Hamilton

Department of Health Sciences
University of York
York, UK What is the background for this study? What are the main findings?

Response: This review looked back over 40 years of research on the links between cannabis and psychosis to examine how knowledge has developed on this issue.

The review found that there is sufficient evidence to suggest a dose response relationship exists in the risk for developing a psychosis that would not have happened if the individual had not been exposed to cannabis. Also for people with schizophrenia cannabis exacerbates their symptoms and prolongs recovery. What should readers take away from your report?

Response: Cannabis use does elevate the risk of psychosis but that risk is rarer than we thought, to put this in perspective we would need to stop 23,000 young people trying cannabis to prevent one case of psychosis. What recommendations do you have for future research as a result of this study?

Response: Future research should focus on higher potency cannabis and any association with psychosis as most of the studies to date have either not included higher potency cannabis or were conducted at a time when population exposure was mainly to lower potency cannabis. Is there anything else you would like to add?

Response: The greatest health risk for people who use cannabis continues to be exposure to tobacco when a cannabis is combined with tobacco in a joint. Thank you for your contribution to the community.


Hamilton, I. (2017) Cannabis, psychosis and schizophrenia: unravelling a complex interaction. Addiction, doi: 10.1111/add.13826.

Note: Content is Not intended as medical advice. Please consult your health care provider regarding your specific medical condition and questions.

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