Investigators at McGill University Health Centre and McGill University in Montreal and the University of British Columbia in Vancouver reviewed 23 clinical investigations of medicinal cannabinoid drugs (typically oral THC or liquid cannabis extracts) and eight observational studies conducted between 1966 and 2007. Authors concluded that subjects given medical cannabis experienced a slightly higher risk of experiencing "nonserious adverse events," specifically dizziness, compared to non-using controls.

By contrast, investigators "did not find a higher incidence rate of serious adverse events associated with medical cannabinoid use." Responding to the study, NORML Deputy Director Paul Armentano said: "Cannabinoids possess a safety profile that is unmatched by virtually every other available prescription drug or over-the-counter medication, including aspirin. To think that almost no serious adverse side effects have been associated with drug's medicinal use over a 30-year period is remarkable. What other medications can make such a claim?"

For more information, please contact Paul Armentano, NORML Deputy Director. Full text of the study, "Adverse effects of medical cannabinoids: a systematic review," appears in the Canadian Medical Association Journal.