The impact of cannabis and cannabinoids for medical conditions on health-related quality of life: A systematic review and meta-analysis.

Introduction: The use of cannabis or cannabinoids to treat medical conditions and/or alleviate symptoms is increasingly common. However, the impact of this use on patient reported outcomes, such as health-related quality of life (HRQoL), remains unclear. Methods: We conducted a systematic review and meta-analysis, employing guidelines from Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We categorized studies based on design, targeted disease condition, and type of cannabis or cannabinoid used. We scored studies based on quality and risk of bias. After eliminating some studies because of poor quality or insufficient data, we conducted meta-analyses of remaining studies based on design. Results: Twenty studies met our pre-defined selection criteria. Eleven studies were randomized controlled trials (RCTs; 2322 participants); the remaining studies were of cohort and cross-sectional design. Studies of cannabinoids were mostly RCTs of higher design quality than studies of cannabis, which utilized smaller self-selected samples in observational studies. Although we did not uncover a significant association between cannabis and cannabinoids for medical conditions and HRQoL, some patients who used them to treat pain, multiple sclerosis, and inflammatory bower disorders have reported small improvements in HRQoL, whereas some HIV patients have reported reduced HRQoL. Conclusion: The relationship between HRQoL and the use of cannabis or cannabinoids for medical conditions is inconclusive. Some patient populations report improvements whereas others report reductions in HRQoL. In order to inform users, practitioners, and policymakers more clearly, future studies should adhere to stricter research quality guidelines and more clearly report patient outcomes.