Prevalence, reasons, perceived effects, and correlates of medical marijuana use: A review

- Marijuana use for medical purposes was found among diverse patient groups.
- Pain was the most commonly endorsed reason for medical marijuana use.
- Medical marijuana appeared to relieve self-reported pain/anxiety for some patients.
- Studies are needed to understand long-term outcomes of medical marijuana use.
- Non-medical marijuana use was positively associated with medical marijuana use.

BackgroundThe use of marijuana for medical purposes is now legal in some U.S. states and other jurisdictions, such as Canada, and Israel. Despite the widespread legalization of medical marijuana globally, there is limited information on patterns and correlates of medical marijuana use (MMU). We conducted a literature review to assess prevalence, reasons, perceived effects, and correlates of MMU among adolescents and adults.MethodsWe searched peer-reviewed articles in English between January 1996 and August 2016 from several databases (PubMed, Google Scholar, Embase, CINAHL, and PsycINFO) using different combinations of keywords.ResultsA total of 25 articles met the inclusion criteria. In the U.S., national survey estimates of prescribed MMU was 1.1% among 12th graders and 17% among adults who reported past-year marijuana use. The reported prevalence of prescribed MMU ranged from <1.7% in Israeli cancer patients to 17.4% in American health care patients. The reported prevalence of self-medication with marijuana ranged from 15% in Canadian patients with chronic pain to 30% in British patients with multiple sclerosis. Pain was the most frequently endorsed reason for use. MMU appeared to provide symptom relief for a range of pain conditions, sleep disturbance, and anxiety symptoms, but it did not appear to provide sufficient relief of cluster headache symptoms. Non-medical marijuana use was a common factor associated with MMU across studies.ConclusionEither MMU or self-medication with marijuana was common, mainly due to pain management. Additional research is needed to evaluate temporal and causal associations of non-medical marijuana use with MMU.