| Increasing use of cannabis for therapeutic purposes raises safety concerns; however, epidemiological studies have not been conducted to specifically evaluate the safety of herbal cannabis used for medical purposes. Available safety information comes primarily from either observational studies that focus on recreational use or from randomized controlled trials (RCTs) that emphasize efficacy as the primary study objective.;This thesis improves our knowledge about adverse events associated with medical cannabis (pharmaceutical cannabinoid products and herbal cannabis), and contributes to the discussion concerning its therapeutic uses from a safety point of view. The consistency of results from our meta-analysis and the COMPASS study allows us to more firmly conclude that medical cannabis was associated with an increased risk of non-serious adverse events (AEs), in particular in relation to the nervous system and psychiatric disorders, compared to controls. However, the evidence regarding the presence or absence of a potential risk of serious adverse events, among patients on cannabis compared with controls, is inconclusive because the study lacks power.;In conclusion, the results suggest the adverse effects of medical cannabis among experienced users are modest. Further studies with systematic long-term follow-up are required to characterize safety issues among new cannabis users and the risk of serious adverse events.;This thesis seeks to improve our understanding of the safety of medical cannabis use. Existing safety information was first assessed in a meta-analysis of all cannabinoid RCTs and a separate systematic review of recreational cannabis. Following this, a prospective cohort study [Cannabis for the Management of Pain, Assessment of Safety Study (COMPASS)] was then conducted. A total of 215 subjects (chronic pain patients who used cannabis provided by Health Canada in the study) and 216 controls (who did not use cannabis) were recruited from across Canada. Adverse events were collected over a one-year period to assess the safety of herbal cannabis for the treatment of chronic pain. In considering the most efficient strategy to control for potential confounders in the development of COMPASS, the statistical efficiency of matching and a multiple model with an adjustment for confounders were compared in a separate project. |
