Purpose: To compare cannabis enthusiasts' knowledge about cannabis risks and effectiveness in treating medical conditions with existing empirical evidence.
Design: A brief survey assessed cannabis use, information sources, and knowledge about risks and effectiveness.
Setting: A cannabis advocacy event in April 2019 in a state with legal medical and recreational cannabis.
Participants: Demographically diverse adults (N = 472) who frequently used cannabis; 85% used cannabis for health or medical purposes.
Measures: Participants reported the sources of their cannabis information, health conditions they thought cannabis was effective in treating (n = 10), and health risks increased by cannabis (n = 6). Conditions and risks were based on ratings of evidence (ie, from substantial to insufficient) for therapeutic effects and risks identified in a review by The National Academies of Sciences, Engineering, and Medicine (NASEM, 2017).
Analyses: Chi-square tests examined the correspondence between participants' knowledge and NASEM conclusions.
Results: Most participants' (95% confidence interval [CI]: 74%-81%) knowledge of cannabis was from their own experiences; 18% (95% CI: 14%-21%) received information from primary care providers. On average, participants' beliefs matched NASEM conclusions for half of effectiveness (95% CI: 50%-53%) and risk items (95% CI: 55%-57%). Many (95% CI: 38%-42%) thought that cannabis use did not increase any risk. Contrary to NASEM conclusions, many thought cannabis was effective in treating cancer (76%), depressive symptoms (72%), and epilepsy (68%). Those who received cannabis information from their primary care providers had better knowledge of medical effectiveness. Medicinal cannabis use frequency inversely predicted knowledge of medical effectiveness and increased risks of adverse events.
Conclusion: There were considerable discrepancies between cannabis users' knowledge and available evidence, highlighting the need for more research and education (by physicians, caregivers, and dispensaries) on effectiveness and health risks, especially for users with specific health issues such as pregnant women and people with depression.
Keywords: cannabis; education/communications; effectiveness; marijuana; risk factor.