By: Candice Tang, UHN Trainee and ORT Times Writer
Nearly 19% of Canadians over age 18 experience chronic pain (1), a hard-to-treat condition that can substantially reduce one’s quality of life. Such debilitating pain may lead to the development of depression, anxiety, and sleep disorders (2,3).
Chronic pain can be managed with prescription opiates, yet, according to a European Consensus Report, nearly 40% of people find that their pain is inadequately managed by conventional treatments (4). Osteoarthritis (OA), the most common type of musculoskeletal disease and a common source of chronic pain, is associated with nerve damage, inflammation, and chronic pain in joints. Non-steroidal anti-inflammatory drugs are commonly used to treat OA, but long-term use can lead to a higher risk of cardiovascular or gastrointestinal events (2). Moreover, individuals with comorbid psychological and pain disorders are more likely to misuse drugs, bringing them farther away from the solution (5). More effective analgesics with lower abuse potential are critical for the management of chronic pain.
Cannabis sativa is well-known for its euphoric effects when used recreationally. Interestingly, the psychoactive component of cannabis, tetrahydrocannabinol (THC), is the same compound that produces analgesic effects. The endocannabinoid system, the body’s natural analgesic system, significantly overlaps with the opioidergic system, partly explaining why cannabis treatment may be effective for pain relief (6). Indeed, the primary cannabinoid receptors are found in the synovial tissue and can be stimulated by exogenous cannabinoids. Cannabinoid treatment reduced pain and inflammation according to some animal models of OA (2).
While medical cannabis use is high among people with arthritis (7), there have been few clinical trials to examine its efficacy to treat chronic pain. For example, trials are limited by small sample size and use of synthetic cannabinoid products rather than recreational cannabis.
Moreover, not all trial results are in agreement. A systematic review of 18 clinical trials showed that over 80% of the trials demonstrated effective pain relief with the treatment of synthetic cannabinoids (2). Another study found that over 30% of patients treated with oral cannabis in addition to prescription opiates discontinued treatment due to inefficacy or adverse side effects. Despite this, the researchers concluded that adjunct cannabis therapy can augment the analgesic effects of opioids, and potentially reduce opioid use over time (3). In the same study, some patients reported decreased symptoms of depression and anxiety (3). Currently, most physicians do not recommend medical cannabis as a first-line treatment option for chronic pain and recent medical residents receive no training on prescribing medical cannabis (7).
The prevalence of chronic pain and the rise of medical and recreational cannabis use urges the scientific community to learn more about the effects of cannabis on our health.
References:
1. Schopflocher, D., P. Taenzer, and R. Jovey. 2011. The prevalence of chronic pain in Canada. Pain Res. Manag. 16: 445–50.
2. O’Brien, M., and J. J. McDougall. 2018. Cannabis and joints: scientific evidence for the alleviation of osteoarthritis pain by cannabinoids. Curr. Opin. Pharmacol. 40: 104–109.
3. Poli, P., F. Crestani, C. Salvadori, I. Valenti, and C. Sannino. Medical Cannabis in Patients with Chronic Pain: Effect on Pain Relief, Pain Disability, and Psychological aspects. A Prospective Non randomized Single Arm Clinical Trial. Clin. Ter. 169: e102–e107.
4. Baker, M., B. Collett, A. Fischer, V. Herrmann, F.J.P.M. Huygen, T. Tolle, P. Trueman, G. Varrassi, P. Vazquez, and K.C.J. Vos. 2010. Pain proposal: Improving the current and future management of chronic pain. Retrieved from https://www.dgss.org/fileadmin/pdf/Pain_Proposal_European_Consensus_Repo....
5. Sutherland, A. M., J. Nicholls, J. Bao, and H. Clarke. 2018. Overlaps in pharmacology for the treatment of chronic pain and mental health disorders. Prog. Neuro-Psychopharmacology Biol. Psychiatry 87: 290–297.
6. Wiese, B., and A. R. Wilson-Poe. 2018. Emerging Evidence for Cannabis’ Role in Opioid Use Disorder. Cannabis cannabinoid Res. 3: 179–189.
7. Katz-Talmor, D., I. Katz, B.-S. Porat-Katz, and Y. Shoenfeld. 2018. Cannabinoids for the treatment of rheumatic diseases — where do we stand? Nat. Rev. Rheumatol. 14: 488–498.