Wang and colleagues performed a systematic review of safety studies of medical cannabinoids published over the past 40 years and found that short-term use appeared to increase the risk of non-serious adverse events. Of all non-serious adverse events, dizziness was the most common (15.5%).
"We found that the rate of non-serious adverse events was 1.86 times higher among medical cannabinoid users than among controls," state the authors. "However, we did not find a higher incidence rate of serious adverse events associated with medical cannabinoid use." The authors note that 99% of the serious adverse events from randomized controlled trials were reported in only 2 trials, a fact the authors say suggests that more studies are required to further characterize safety issues.
In a related commentary, Dr. Louisa Degenhardt, Professor of Epidemiology, National Drug and Alcohol Research Centre, University of New South Wales, Sydney, Australia ( l.degenhardt@unsw.edu.au ), states that, although the side effects of oral cannabis therapy appear to be minor in the short term, their longer-term effects, particularly in the setting of chronic illness, have yet to be studied.
Canadian Medical Association Journal