Cannabis has been used for  centuries both as a recreational drug for its mind altering properties, and as a medicine for its ability to relieve various physical or mental complaints (Bostwick, 2012). However, until half a century ago, very little was known about how cannabis works in the human body and brain.

We now know that humans and other animals have an endocannabinoid system that extends throughout the body. This system encompasses receptors that bind to both external cannabinoids and endocannabinoids made by our own bodies.  (Wilson and Nicoll, 2002, Howlett et al, 2004). The cannabinoids produced internally are released on demand and help to regulate numerous physiological processes, including pain (Russo and Hohmann, 2013).

The cannabis plant produces cannabinoids that are similar to the endocannabinoids produced by our own bodies. Research has demonstrated that cannabinoids from plants can alleviate pain that does not respond to traditional treatments (Mackie, 2006, Russo and Hohmann, 2013, Watson et al, 2000, Ben Amar, 2006).

Cannabinoids external to our bodies can help manage pain

There are more than 100 naturally occurring chemical compounds, called cannabinoids, produced by the cannabis plant, but only two have been well characterized pharmacologically: Delta 9-tetrahydrocannabinol, known as THC, and cannabidiol, or CBD.

Cannabinoids produced by plants have been found to be clinically useful for chronic pain management, and work by directly or indirectly modulating cannabinoid activity.

THC and CBD have several therapeutic indications, including the treatment of chronic pain (Aggarwal, 2013, Lynch et al, 2011; Russo, 2008) and intractable pain related to:

  • Multiple sclerosis (Zajicek et al, 2003; Rog et al, 2005, 2007; Wade et al, 2006)
  • Cancer (Johnson et al, 2010)
  • Fibromyalgia (Fiz et al, 2011)
  • HIV (Abrams et al, 2007; Ellis et al, 2009)
  • Neuropathic pain (Attal et al, 2004; Ware et al, 2010; Wilsey et al, 2008)

THC is also the agent responsible for the psychoactive effects of cannabis. These effects – sought by recreational users – are the most frequently mentioned reason for discontinuation of medicinal cannabis use among patients, since they compromise the level of functionality in a patient’s everyday life.

However, CBD has the unique ability to inhibit THC’s psychoactive effects, minimizing THC side effects such as euphoria, memory loss, paranoia, and anxiety (Bhattacharya et al, 2010, Russo, 2011, McPartland and Russo, 2001). Medicinal cannabis is best tolerated when high levels of CBD are present.

Medicinal cannabis safety and potential side effects

Cannabis is a relatively safe medication when compared to many of the prescription drugs widely used to control chronic or intractable pain.  Unlike opioid-based medications such as oxycodone (Oxycontin) and hydrocodone (Vicodin), cannabis will not result in an overdose death. This does not mean, however, that there are no risks:

Routes of administration

Cannabis can be smoked or vaporized; ingested in food or beverages; absorbed sublingually; or used topically. How cannabis is administered determines how quickly therapeutic effects will be felt and how long the effects will last. More information about the routes of administration can be found in the brochure Medicinal Cannabis & Chronic Pain: Information for Patients.

Medicinal cannabis in Washington State: What is the law?

In Washington State, clinicians are allowed to recommend the use of medicinal cannabis. [Washington State RCW 69.51a]. As of July 1, 2016, rules stemming from the Cannabis Patient Protection Act have been implemented. Visit the Washington State Department of Health’s Medical Marijuana page to learn more about the CPPA and associated elements, such as the authorization database, medical cannabis consultant, recognition card, authorization form, and more.

Where to learn more


  • Abrams DI, et al. Cannabis in painful HIV-associated sensory neuropathy: a randomized placebo-controlled trial. Neurology 2007;68(7):515–521. View abstract
  • Aggarwal SK. Cannabinergic pain medicine: a concise clinical primer and survey of randomized-controlled trial results. Clin J Pain 2013;29(2):162-171.  View abstract
  • Attal N, et al. Are oral cannabinoids safe and effective in refractory neuropathic pain? Eur J Pain 2004;8:173-7. View abstract
  • Ben Amar M. Cannabinoids in medicine: a review of their therapeutic potential. J Ethnopharmacol 2006;105(1-2):1-25.  View abstract
  • Bhattacharyya S, et al. Opposite effects of delta-9-tetrahydrocannabinol and cannabidiol on human brain function and psychopathology. Neuropsychopharmacology 2010;35(3):764-74. Free online
  • Bostwick JM. Blurred boundaries: the therapeutics and politics of medical marijuana. Mayo Clin Proc. 2012;87(2):172-186. Free online
  • Ellis RJ, et al. Smoked medicinal cannabis for neuropathic pain in HIV: a randomized, crossover clinical trial. Neuropsychopharmacology 2009;34(3):672-680. Free online
  • Fiz J, Durán M, Capellà D, Carbonell J, Farré M. Cannabis use in patients with fibromyalgia: effect on symptoms relief and health-related quality of life. PLoS One. 2011 Apr 21;6(4):e18440. View abstract
  • Howlett AC, Breivogel CS, Childers SR, Deadwyler SA, Hampson RE, Porrino LJ.  Cannabinoid physiology and pharmacology: 30 years of progress. Neuropharmacology 2004;47 Suppl 1:345-58.  View abstract
  • Johnson JR, et al. Multicenter, double-blind, randomized, placebo-controlled, parallel-group study of the efficacy, safety, and tolerability of THC: CBD extract and THC extract in patients with intractable cancer-related pain. J Pain Symptom Manage 2010;39(2):167-79. View abstract
  • Lynch ME, Campbell F. Cannabinoids for treatment of chronic non-cancer pain; a systematic review of randomized trials. Brit J Clin Pharmacol 2011;72(5):735-744. Free online
  • Mackie K. Cannabinoid receptors as therapeutic targets. Annu Rev Pharmacol Toxicol 2006;46:101-22. View abstract
  • McPartland JM, Russo EB. Cannabis and cannabis extracts: greater than the sum of their parts? Co-published simultaneously in Journal of Cannabis Therapeutics 2001;1(3/4)103-132; and: Cannabis Therapeutics in HIV/AIDS (ed: Ethan Russo) Haworth Integrative Healing Press, pp. 103-132, 2001.
  • Rog DJ, Nurmikko TJ, Friede T, Young CA. Randomized, controlled trial of cannabis-based medicine in central pain in multiple sclerosis. Neurology 2005 ;65(6):812-819. View abstract
  • Rog DJ, Nurmikko TJ, Young CA. Oromucosal delta9-tetrahydrocannabinol/cannabidiol for neuropathic pain associated with multiple sclerosis: an uncontrolled, open-label, 2-year extension trial. Clin Ther 2007;29(9):2068-2079. View abstract
  • Russo EB. Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects. Br J Pharmacol 2011;163(7):1344-64. Free online
  • Russo EB, Hohmann AG. Role of cannabinoids in pain management. In: Comprehensive Treatment of Chronic Pain by Medical, Interventional, and Integrative Approaches 2013, 181-197. View abstract
  • Russo EB. Cannabinoids in the management of difficult to treat pain. Ther Clin Risk Manag 2008;4(1):245-259. Free online
  • Wade DT, Makela PM, House H, Bateman C, Robson P. Long-term use of a cannabis-based medicine in the treatment of spasticity and other symptoms in multiple sclerosis. Mult Scler 2006;12(5):639-645. View abstract
  • Ware MA, et al. Smoked cannabis for chronic neuropathic pain: a randomized controlled trial. CMAJ 2010;182(14):E694-E701. Free online
  • Watson SJ, Benson JA, Joy JE. Marijuana and medicine: assessing the science base: a summary of the 1999 Institute of Medicine report. Arch Gen Psychiatry 2000;57(6):547-555. View abstract
  • Wilsey B, et al. A randomized, placebo-controlled, crossover trial of cannabis cigarettes in neuropathic pain. J Pain 2008;9(6):506-521. View abstract
  • Wilson RI, Nicoll RA. Endocannabinoid signaling in the brain. Science 2002;296(5568):678-82.  View abstract
  • Zajicek J, et al. Cannabinoids for treatment of spasticity and other symptoms related to multiple sclerosis (CAMS study): Multicentre randomized placebo-controlled trial. Lancet 2003;362(9395):1517-1526. View abstract

Updated 2015. This information adapted with permission from the National Cannabis Prevention and Information Centre in Australia.