“I have a patient, a school teacher, who uses medical marijuana. It keeps her working. She takes a few puffs during the day, goes back to the classroom and she’s fine. Without it, she

Mary-Ann Fitzcharles, MB, ChB, Associate Professor of Rheumatology at McGill University

Mary-Ann Fitzcharles, MB, ChB, Associate Professor of Rheumatology at McGill University

can’t function. All our patients are different.” Announced a rheumatologist from Israel, after asking how doctors should try to differentiate patients who are at risk of abusing the drug. Another Rheumatologist stomped up to the microphone, but before asking her question to the speaker, she made sure to look at the doctor from Israel and say, “I’m appalled that a teacher is using marijuana during the school day. If a child I loved were in that class I’d be absolutely disgusted. Kids are smart. They know what’s going on.” The verbal exchange, after a discussion of the medical and political issues surrounding use of medical marijuana in Canada given by Mary-Ann Fitzcharles, MB, ChB, Associate Professor of Rheumatology at McGill University, was a concise example of the hotly-debated use of cannabis in medicine. At the American College of Rheumatology Conference 2014 in Boston, two rheumatologists and one lawyer gave lectures on the use of cannabis in treating chronic pain associated with rheumatic diseases.


Caveats in Research

Up until recently, marijuana was a difficult substance for most researchers to get their hands on. For this reason, very few researchers studied the drug’s effects until very recently. For ethical reasons, researchers generally do not give the drug to people who have not previously used it on their own. This effect confounds a great majority of the research, preventing researchers from being able to distinguish effects of the drug from pre-existing conditions. The most common strategy to avoid this complication is to use animals as models, hoping that the observed effects translate to humans.

Cannabis contains more than 40 active compounds, several of them cannabinoids which act on our endocannabinoid receptors. Each strain has different concentrations of each active ingredient. Consistent dosing is very unlikely. Many studies observe the effects of one particular strain of the drug which is often inconsistent or not representative of what a patient might receive upon being prescribed cannabis.



The receptors in our brains and bodies that respond to cannabinoids are part of the endocannabinoid system. This system functions in a variety of ways. It has effects on appetite, memory, immune function, stress, and pain. It is possible, that cannabis could have positive effects on some of these receptors.

In the United States, medical marijuana is currently approved for use in post-chemotherapy nausea and vomiting, as well as AIDS-induced anorexia. Other countries have approved cannabinoids for more indications. Research has shown that it is an effective treatment in seizure disorders, and many recommend its use in the treatment of Multiple Sclerosis. (Koppel et al 2014)

A synthetic cannabinoid called Resunab is currently in trials for autoimmune disorders and neuropathic pain. Some research in animal models shows that cannabis can have analgesic effects and reduce inflammation. (Baker and McDougel 2009) A review of studies that used different forms of cannabinoids or smoked cannabis showed that cannabis may be effective in reducing pain in illnesses where the pain was centralized in the nervous system. Examples of this type of pain come from fibromyalgia and tension headaches. There is little evidence that marijuana is effective in treatment of rheumatoid or Osteo- arthritis pain. (Koppel et al 2014)

According to Dr. FItzcharles, in Canada, where medical marijuana is federally legalized, ⅔ of patients who use it cite “severe arthritis” as the reason they need it.



The majority of patients who are currently using marijuana for medicinal purposes were using it for recreational purposes first. This leaves doctors concerned about the potential of their patient blurring the lines between therapeutic effects and getting high.

Smoking marijuana has been shown to increase reaction time, evidence that driving under the influence of marijuana can lead to devastating car accidents. A meta-analysis in the Netherlands showed that the chances of being seriously injured or killed in a car accident was doubled if the driver had smoked marijuana. Smokers also show reduced cognitive function such as short term memory deficits lasting 5 hours after use. (Asbridge et al 2012)

Animal studies suggest that marijuana leads to withdrawal symptoms and addictive behaviors in rats. (Lupica et al, 2004) THC, the compound known for causing the “high” associated with cannabis, can alter the dopaminergic reward system in the brain. This system is responsible for feelings of happiness and motivation. Use of cannabis (and other drugs) reduce the sensitivity of this system, making it harder for users to feel good in the future. It is important to note that while marijuana does carry a risk of addiction, so do many other drugs used for treating pain.

Marijuana use is often associated with increased rates of mental illness. However, as mentioned before, it is very difficult to distinguish cause and effect between these two factors. There is substantial evidence that in patients with a genetic predisposition to schizophrenia, marijuana can lead to extreme psychosis. This observation is of particular concern for doctors treating younger patients, because they may not know that they have a genetic predisposition to schizophrenia until later in life. (Radhakrishnan et al 2014)

Lastly, in patients who smoke marijuana, there is an increased risk of respiratory illness. Patients tend to have an increased likelihood of chronic bronchitis, lung cancer, and cancer of the upper portions of the aerodigestive tract. These effects would likely be erased if the drug was administered in a different fashion. (Hall and Degenhardt, 2013)


Suggestions for Necessary Improvements

Many rheumatologists are not confident with the information they have on medical marijuana. (Fitzcharles 2013) There is little data to help the doctor choose an appropriate dose of each active compound in the drug, and even if they do, a patient may end up with a totally different strain and composition when they speak with a distributor. Nonetheless, patients will continue to put pressure on their doctors to describe the drug as it becomes legal. Both speakers agreed that marijuana should not be the first drug prescribed to a patient dealing with chronic pain. It should only be discussed after several other therapies have failed.

Most doctors and researchers can agree that medical marijuana has the potential to have a variety of therapeutic uses, especially for certain types of chronic pain. Nonetheless, more research is warranted. Both speakers at the conference suggested that clinical trials continue with extractions from the plant and synthetic cannabinoid compounds. Thorough trials would allow doctors to comfortably recommend specific compounds and consistent doses for particular therapeutic purposes. This would also negate the deleterious respiratory effects of smoking marijuana, since the patient would not need to smoke these compounds. After his discussion of the great potential uses and misuses of medical marijuana Daniel J Clauw, M.D. Professor of Anesthesiology, Rheumatology, and Psychology, as well as the Director of  the Chronic Pain and Fatigue Research Center at the University of Michigan said, “I don’t think anyone in the year 2014, if they’re trying to use cannabis for medicinal purposes, should be smoking in the classic way… It makes absolutely no sense.”



Koppel et al, 2014, Neurology: 82: 1556-63

Baker and McDouggal 2009, British Journal of Pharmacology 142, 1361–1367

Radhakrishnan, 2014, Frontiers in Psychiatry: 5(54): 1-6

Hall, W. Drug Test Analysis 2013, 6:39-452

Asbridge et al, 2012 BMJ, 344e: 546

Lupica et al, 2004, British Journal of Pharmacology, 143:227-234

Fitzcharles, ACR2013