Clearing the Air About Cannabis: Medical Cannabis |

Search form

Clearing the Air About Cannabis: Medical Cannabis

Tuesday, December 3, 2019 - 09:44

We have received multiple questions on the evidence behind medical cannabis, so have broadened the scope of this month’s issue to provide you with some answers.

Read on to learn more about medical cannabis, how to approach and support conversations with students or other teachers, and resources available for further learning on this topic.

What is medical cannabis?

The use of cannabis for medical purposes was approved in Canada in 2001 through the Marihuana Medical Access Regulations (MMAR).1 To access medical cannabis, Canadians need to obtain medical authorization from a health care provider. There are specific regulations that pose limits on cannabis possession and cultivation for medical purposes.2

The term medical cannabis refers to the cannabis plant or its extracts and pharmaceutical formulations that include CBD or THC. In Canada, medical cannabis includes3:

  • medications such as Nabilone or Dronabinol, which can offer a reliable dose for treatment of specific conditions;
  • cannabis containing preparations made by a government-licensed producer;
  • dried cannabis that is either home grown or purchased from a government licensed producer that is then either inhaled or consumed through edibles; and
  • cannabis oil that can be taken orally with food, inhaled or applied to the skin directly.

What is the evidence for medical cannabis?

Medical cannabis is currently approved for the following conditions, which have scientific evidence demonstrating its benefits: 3, 4

  • anti-nausea relief for nausea caused by cancer and HIV treatments;
  • increasing appetite for AIDS patients;
  • pain relief for pain caused by nervous system disorders, multiple sclerosis, advanced cancer and other conditions. 

However, it’s important to note that for those approved uses, cannabis is not recommended as a first line option. This means that clients are encouraged to first use other medications for which there is more evidence, and only try cannabis if those have not proven helpful.3

Current research is investigating medical cannabis for a multitude of other proposed uses. In these cases, the evidence is less clear on whether cannabis is effective, with lots of variation between studies. Some of the proposed uses include: 3,5

  • decreasing muscle spasms and not just pain due to multiple sclerosis;
  • treatment of epilepsy, especially in children;
  • anti-inflammatory uses for inflammatory bowel disease;
  • post-traumatic stress disorder (PTSD);
  • psychosis;
  • anxiety or mood disorders; and
  • substance use disorders.

It’s important to remember that for the approved and proposed uses described above, cannabis acts mainly to relieve the symptoms of the disease without actually curing the underlying disease. 3

Does cannabis have side effects?

There is little research on the adverse effects and risks associated with using medical cannabis. However, research on consuming cannabis long term for non-medical reasons has shown the following risks: 3, 7  

  • psychosis;
  • neurocognitive deficits, such as working memory deficits;
  • respiratory ailments and cancers;
  • cannabinoid hyperemesis syndrome, marked by frequent vomiting;
  • cannabis use disorder; and
  • heart attacks.

Who shouldn’t use cannabis?

As cannabis can have adverse effects, there are groups who are advised not to use it. There is emerging consensus that cannabis is not recommended for the following groups: 3, 6

  • children and adolescents, as brain development is not yet complete. Exceptions may be made for children with severe forms of epilepsy who respond to CBD-only medications and have not responded to other treatments;
  • pregnant and breastfeeding people;
  • those who have a history of problematic substance use or psychosis; and
  • those with certain pre-existing heart conditions.

What should educators know?

According to the 2017 Ontario Student Drug Use and Health Survey (OSDUHS), 7% of secondary students have used cannabis to manage pain, nausea or other medical problems.8

Exploring the topic of medical marihuana as part of the healthy living curriculum helps inform students about the evidence behind medical cannabis and understand that it’s not risk free; particularly in light of the evidence regarding brain development and that cannabis is not recommended for anyone under 18. Providing students with opportunities to examine the current media marketing strategies promoting the health benefits of cannabis and the companies that promote cannabis use helps students to critically think about this emerging issue, develop an informed perspective, and make informed decisions about their own health and well-being.

If you want more information on medical cannabis, the Canadian Centre on Substance Use and Addiction (CCSA) has released a report on the evidence behind medical cannabis, which can provide additional information on the evidence and risks associated with medical cannabis.

For access to a database of resources visit Ophea’s Cannabis Education Resources. You can also sign up for Ophea’s monthly eConnection e-newsletter to read future issues of this Q&A column and to stay up-to-date with the latest events and resources – including the recent launch of Ophea’s Cannabis Education: Activate the Discussion Elementary and Secondary Discussion Guides! Visit Ophea’s Clearing the Air About Cannabis Q&A Form to submit your questions for January’s Q&A column.

Thank you!
Ophea and the Provincial System Support Program at CAMH



  1. Government of Canada. (2019). Understanding the New Access to Cannabis for Medical Purposes Regulations. Available:
  2. Government of Canada. (2019). For People Registered Or Designated To Produce Cannabis For Medical Purposes.  Available:
  3. Canadian Centre on Substance Use and Addiction (CCSA). (2016). Clearing the Smoke on Cannabis: Medical Use of Cannabis and Cannabinoids – An Update. Available:
  4. Health Canada. (2018). Information for Health Care Professionals: Cannabis (marihuana, marijuana) and the cannabinoids. Available: 
  5. McMaster University. (2017). What role does medical cannabis play in treating anxiety and mood disorders?. Available:
  6. McMaster University. (2017). Who shouldn't use medicinal cannabis?.  Available:
  7. Volkow, N.D., Baler, R.D., Compton, W.M. & Weiss, S.R. (2014). Adverse health effects of marijuana use. The New England journal of medicine, 370(23), 2219–2227. doi:10.1056/NEJMra1402309. Available:
  8. Boak, A., Hamilton, H., Adlaf, E.M. & Mann, R.R. (2017). Drug use among Ontario students, 1977-2017: Detailed findings from the Ontario Student Drug Use and Health Survey (OSDUHS). Toronto, ON: Centre for Addiction and Mental Health. Available: