Prevalence and self-reported reasons of cannabis use for medical purposes in USA and Canada

Psychopharmacology (Berl). 2022 May;239(5):1509-1519. doi: 10.1007/s00213-021-06047-8. Epub 2022 Jan 12.


Rationale: There has been increasing attention on cannabis use for medical purposes, but there is currently a lack of data on its epidemiology.

Objectives: To examine the epidemiology of self-reported cannabis use for medical purposes by (1) estimating its prevalence, (2) comparing gender and age differences, and (3) investigating what reasons they were used to manage.

Methods: Participants included 27,169 respondents (aged 16-65) who completed Wave 1 of The International Cannabis Policy Study (ICPS) conducted across Canada and the USA in 2018 via online surveys. Cannabis policy conditions were "US legal-recreational" (legal for both recreational and medical uses), "US legal-medical only", "US illegal", and "Canada-medical only".

Results: The overall prevalence of self-reported ever cannabis use for medical purposes was 27%, with similar rates by sex and the highest prevalence in young adults. Prevalence was higher in US legal-recreational states (34%) than US illegal states (23%), US legal-medical only states (25%), and Canada (25%). The most common physical health reasons include use to manage pain (53%), sleep (46%), headaches/migraines (35%), appetite (22%), and nausea/vomiting (21%). For mental health reasons, the most common were for anxiety (52%), depression (40%), and PTSD/trauma (17%). There were 11% who reported using cannabis for managing other drug or alcohol use and 4% for psychosis.

Conclusions: A substantial proportion of the North American population self-reported cannabis use for medical purposes for a variety of medical reasons, including those living in jurisdictions without legal markets. Further research is needed to understand the safety and efficacy of these forms of medical cannabis use.

Keywords: Cannabis; Epidemiology; Legalisation; Marijuana; Prevalence; Therapeutic use.

MeSH terms

  • Analgesics
  • Canada / epidemiology
  • Cannabinoid Receptor Agonists
  • Cannabis*
  • Hallucinogens*
  • Humans
  • Medical Marijuana* / therapeutic use
  • Prevalence
  • Self Report
  • Young Adult


  • Analgesics
  • Cannabinoid Receptor Agonists
  • Hallucinogens
  • Medical Marijuana