Fact or fiction: What the research says about cannabis use for common conditions

The Bottom Line

  • The use of cannabis amongst older adults in Canada continues to increase, with much of this use being for medical purposes.  
  • Although some benefits can be seen with the use of cannabis and cannabis-based products for common conditions such as cancer, nerve pain, and inflammatory bowel disease, they are hindered by potential negative side effects.
  • Currently, the quality of the evidence is low and more high quality research is needed to establish more definitive recommendations on use. 
  • If you are considering the use of cannabis or cannabis-based products for medical reasons, be sure to speak with your health care provider first, so you can assess whether the benefits outweigh the possible harms, ask questions, get answers, and develop a treatment plan. 

Following the legalization of cannabis use in Canada, older adults 65 years old and over have become the fastest growing age group of cannabis consumers in the country. What are older adults using cannabis for? It turns out the majority, 52 % to be exact, use cannabis solely for medical purposes, 24% use it only for non-medical purposes, and 24% use it for a combination of both (1). With an increased interest in cannabis to help treat or cope with various health conditions and side effects of treatments, it is important to be aware of whether or not the evidence supports these claims and the safety of cannabis use. Let’s take a deeper dive into the evidence-base around cannabis use for three common conditions: cancer, chronic nerve pain, and inflammatory bowel disease (IBD). Click on the links below to find out more about the research and myth-busting results.

1. Cannabis for side effects of cancer treatment?

The majority of cancer patients undergoing chemotherapy experience distressing side effects like nausea and vomiting (2;3). The standard approach for dealing with these side effects is the use of anti-sickness medications. Cannabinoids, which are active chemicals found in cannabis, are an alternative approach (4). Research shows that cannabinoids may help people going through chemotherapy manage the accompanying nausea and vomiting, and may even be as effective as the standard approach. However, potential benefits may come with an increased risk of other side effects, such as dizziness, sedation, disorientation, or uneasiness. These findings are based on studies of low to moderate quality. As such, more research that is of higher quality and takes into account newer cancer therapies and anti-sickness medications is needed to increase our certainty in the results (5).

Weeding out the truth: Cannabis-based medications for cancer patients

2. Cannabis for chronic nerve pain?

Nerve pain is caused by nerve damage that stems from a variety of factors, including illness, injury, and even surgery (6;7). It is often treated using pain relieving medications such as non-steroidal anti-inflammatory drugs or opioids, although not generally with a great degree of success (7;8). Research demonstrates that cannabis-based medications may relieve pain and reduce pain intensity, psychological distress, and sleep problems in adults with chronic nerve pain. But, once again, alongside these potential benefits may come unwanted side effects such as confusion, psychosis, and sedation. These findings are grounded in very-low to moderate quality evidence. Therefore, more high quality research is needed to establish effectiveness and safety, especially studies focusing on older populations (8;9).

Cannabis for chronic nerve pain: A half-baked solution?

3. Cannabis for Crohn’s disease and ulcerative colitis?

Crohn’s disease and ulcerative colitis are chronic inflammatory conditions that impact an individual’s digestive tract (10). Both are a type of IBD (11). Treatment often consists of prescription medications that induce and maintain disease remission, but come with an increased risk of serious side effects such as liver problems and cancer (10;12). Research illustrates that cannabis cigarettes and cannabis oil do not appear to help with remission or inflammation in people with active Crohn’s or colitis; however cannabis cigarettes may reduce disease activity in both IBD subtypes, while cannabis oil may enhance quality of life. Certain improvements were accompanied by increased side effects in people with Crohn’s—such as drowsiness, memory loss, and issues with concentration—and colitis—such as headaches, fatigue, and dizziness. It is also important to be aware that these results were based on a small number of studies with a very small number of participants. So, ultimately, no concrete conclusions can be made at this time, and further research is needed (10;13).

Does cannabis offer new hope for folks with Crohn’s disease and ulcerative colitis?

Considerations for cannabis use

Overall, evidence on the use of cannabis and cannabis-based products for cancer, nerve pain, and IBD is limited and comes from fairly low quality research. This makes it difficult to make strong conclusions on effectiveness and safety. The big question you might be asking is, "what does this all mean for me"? First, it means trying to stay up-to-date on the evolving evidence-base around this topic, especially as new research comes out. Second, if you are contemplating using cannabis for medical purposes, remember to discuss the issue with your health care provider before commencing. Lastly, always weigh out the pros and cons for you as an individual. For some people the side effects might outweigh any benefits, while for others the opposite may be true (e.g., people not responding to traditional treatments). This assessment process is something a health professional can help you with, as is the development of a tailored treatment plan.

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  1. Statistics Canada. National Cannabis Survey, third quarter 2019. [Internet] 2019. [cited October 2020]. Available from https://www150.statcan.gc.ca/n1/daily-quotidien/191030/dq191030a-eng.htm 
  2. Schwartzberg LS. Chemotherapy-induced nausea and vomiting: Clinician and patient perspective. J Support Oncol. 2007; 5:5-12.
  3. Russo S, Cinausero M, Gerratana L, et al. Factors affecting patient’s perception of anticancer treatments side-effects: An observational study. Expert Opin Drug Saf. 2014; 13(2):139-150.
  4. Walsh D, Nelson KA, Mahmoud FA. Established and potential therapeutic applications of cannabinoids in oncology. Support Care Cancer. 2003; 11:137-143.
  5. Smith LA, Azariah F, Lavender VT, et al. Cannabinoids for nausea and vomiting in adults with cancer receiving chemotherapy. Cochrane Database Syst Rev. 2015, 11:CD009464. doi: 10.1002/14651858.CD009464.pub2. 
  6. Cohen SP, Mao J. Neuropathic pain: Mechanisms and their clinical implications. BMJ. 2014; 348:f656. doi: 10.1136/bmj.f7656.
  7. Holland K. What you should know about neuropathic pain [Internet]. Healthline, 2017. Available from https://www.healthline.com/health/neuropathic-pain 
  8. Mucke M, Phillips T, Radbruch L, et al. Cannabis-based medicines for chronic neuropathic pain in adults. Cochrane Database Syst Rev. 2018; 3:CD01282. doi: 10.1002/14651858.CD012182.pub2.
  9. McParland AL, Bhatia A, Matelski J, et al. Evaluating the impact of cannabinoids on sleep health and pain in patients with chronic neuropathic pain: A systematic review and meta-analysis of randomized controlled trials. Reg Anesth Pain Med. 2023; 48(4):180-190. doi: 10.1136/rapm-2021-103431. 
  10. Kafil TS, Nguyen TM, MacDonald JK, et al. Cannabis for the treatment of Crohn's disease. Cochrane Database Syst Rev. 2018; 11:CD012853. doi: 10.1002/14651858.CD012853.pub2.
  11. Limketkai BN, Iheozor‐Ejiofor Z, Gjuladin‐Hellon T, et al. Dietary interventions for induction and maintenance of remission in inflammatory bowel disease. Cochrane Database Syst Rev. 2019; 2:CD012839. doi: 10.1002/14651858.CD012839.pub2.
  12. Crohn’s and Colitis Canada. 2018 Impact of Inflammatory Bowel Disease in Canada. 2018. [cited October 2020]. Available form: https://crohnsandcolitis.ca/Crohns_and_Colitis/documents/reports/2018-Impact-Report-LR.pdf 
  13. Kafil TS, Nguyen TM, MacDonald JK, et al. Cannabis for the treatment of ulcerative colitis. Cochrane Database Syst Rev. 2018; 11:CD012954. doi: 10.1002/14651858.CD012954.pub2.

DISCLAIMER: These summaries are provided for informational purposes only. They are not a substitute for advice from your own health care professional. The summaries may be reproduced for not-for-profit educational purposes only. Any other uses must be approved by the McMaster Optimal Aging Portal (info@mcmasteroptimalaging.org).

Many of our Blog Posts were written before the COVID-19 pandemic and thus do not necessarily reflect the latest public health recommendations. While the content of new and old blogs identify activities that support optimal aging, it is important to defer to the most current public health recommendations. Some of the activities suggested within these blogs may need to be modified or avoided altogether to comply with changing public health recommendations. To view the latest updates from the Public Health Agency of Canada, please visit their website.