Personal Health Navigator

The pros and cons of medical marijuana

Question: I threw out my back last year and the pain hasn’t gone away. I tried Tylenol and Advil but they didn’t do anything. I read online that medical marijuana can help with pain like mine and that doctors can prescribe it now, but my doctor says there’s no proof it works. I’m desperate for the pain to go away, how can I find out if marijuana might help?

Answer: Your question is extremely timely. The federal government is changing the way medical marijuana is regulated in Canada. On April 1, patients will no longer apply to Health Canada for permission to use marijuana and they won’t be getting their allotted dose directly from the government. Instead, doctors will be writing prescriptions, just as they do for other medications, and medical marijuana will be supplied by federally-licensed growers.

A lot of doctors feel very uneasy about having more control of this controversial drug placed in their hands. Previously, they had to sign a declaration of need for their patients. But the final say on access rested with Ottawa.

To further complicate matters, many medical professionals still doubt the medicinal value of weed. That certainly seems to be the case with your physician.

So it’s worthwhile reviewing the existing scientific evidence. You may be pleased to learn studies suggest marijuana can be useful in easing some forms of pain.

However, before concluding pot is the solution, you should consider all your medical options. Ask your doctor for a referral to an orthopedic specialist who might be able to pinpoint the cause of your chronic back pain. You may find a combination of physiotherapy and back exercises bring relief. (Or, you may have a problem that requires a surgical solution.)

If that approach doesn’t work, then you may want to once again raise the issue of using marijuana with your doctor. Keep in mind, though, smoking dope could have some undesirable consequences.

“Let’s not pretend this is a substance that is free of harm, but I also don’t think we want to vilify something that actually might help some of our patients. ” says Dr. David Juurlink, a staff physician and drug-safety researcher at Sunnybrook Health Sciences Centre.

Marijuana contains a number of biologically-active cannabinoids including tetrahydrocannabinol, or THC, the famed ingredient that makes people feel high.

There are actually cannabinoid receptors “throughout the brain and most tissues and organs of the body,” writes Dr. Harold Kalant, in a review article in the September edition of The Canadian Journal of Addiction.

“The extremely widespread distribution of the endocannabinoid system throughout the body, and its action on so many different neurotransmitters, explain how the cannabinoids are able to affect such a broad range of physical and mental functions, with both therapeutically useful and potentially harmful effects.”

Much of the earlier marijuana research focused on its negative consequences. So there is only limited high-quality data on its therapeutic benefits, says Dr. Kalant, a professor emeritus at the University of Toronto and the Centre for Addiction and Mental Health.

What can be said with some certainty is that marijuana lessens musculoskeletal and neuropathic (nerve) pain; provides relief from the nausea and vomiting associated with chemotherapy; reduces muscle spasms in Multiple Sclerosis patients; and boosts appetite.

There are a few caveats worth noting, however. “The increase in appetite is mostly for fat and sugar, not protein which you need for [tissue] recovery. But, on the upside, it may help prevent weight loss” in cancer patients who find it hard to eat, says Dr. Kalant.

Furthermore, conventional medications are available to treat all these conditions. So marijuana should not necessarily be the first choice for most patients. Rather, it may be an option to consider when other things fail. Or, it could be useful in combination with other therapies.

“Several clinical studies … have shown that combining smaller doses of cannabinoid and opioid can give good analgesic effect and fewer side effects than a larger dose of either drug alone,” explains Dr. Kalant.

Proponents of medical marijuana have suggested it can help treat numerous conditions, including glaucoma, inflammation and even cancer. There is a lack of evidence to back up many of the claims. What’s more, for some of the ailments, such as glaucoma, patients would have to toke up every three to four hours day and night to maintain therapeutic levels in the bloodstream or tissues. Routinely consuming that much weed would be incapacitating.  

To avoid the harm that can be caused by cannabis smoke, pharmaceutical companies have developed several marijuana-mimicking products that can be taken by mouth, such as Cesamet (nabilone), a capsule approved for the treatment of severe nausea and vomiting in people undergoing cancer chemotherapy; and Sativex (nabiximols), an under-the-tongue spray often prescribed to alleviate neuropathic pain, spasticity, overactive bladder and other symptoms in MS patients. (Cesamet contains a synthetic cannabinoid while Sativex is a mixture of compounds derived from cannabis plants.)

Dr. Kalant has great hopes for the development of medications based on specific cannabinoids that act on only certain body tissues. “It seems highly likely that in the near future a range of new drugs will become available that will provide the desired cannabis-like effects on specific tissues and disease processes, without the unwanted side effects and problems that can be created by smoking crude cannabis,” Dr. Kalant predicts in his CJA article.

And, indeed, the unwanted side effects could be considerable for frequent smokers.

“If you have multiple sclerosis and use cannabis regularly, it can further impair your cognitive abilities,” says Dr. Anthony Feinstein, a neuropsychiatrist at Sunnybrook Health Sciences Centre and a professor at the University of Toronto.

Dr. Feinstein’s research has focused on MS patients who smoke marijuana for pain relief and to reduce the muscle spasms that hinder movement.

These individuals, he explains, are already at risk of suffering cognitive deficits as a result of their neurodegenerative disease. His studies have found MS patients who smoked pot three or more times a week are twice as likely as abstainers to experience cognitive difficulties.

In practical terms, that means they have more trouble remembering things, the speed at which they processed information is slowed and they have greater difficulty solving problems.

In his most recent study, currently under review, Dr. Feinstein and his fellow researchers used functional MRI to compare the brain activity of cannabis smokers and abstainers.

The marijuana users were asked to refrain from smoking it for at least 12 hours before the study so they were technically not “high” when they did skill-testing exercises while their brains were scanned. (Signs of marijuana use can be found in the blood for up to a month after smoking.)

The results of the study revealed an “inefficient and diffused pattern of [mental] activation,” among frequent users of cannabis. “The brain [of a cannabis smoker] is working harder to try to solve problems. And when a problem becomes more complex, they make more mistakes,” compared to the non-users of cannabis.

So far, Dr. Feinstein has assessed a total of 100 MS patients – 60 users and 40 abstainers – who took part in three separate studies. Although a relatively small sample of 100 patients “doesn’t make a watertight argument, it is very compelling that we found the same thing in each study.”

Despite the risks, Dr. Feinstein believes marijuana may still be an appropriate treatment for some MS patients.

“If you have intractable pain and you say to me that cannabis is the only drug that takes away your pain, I am not going to argue with you. But I will say just be aware it may further compromise your cognitive abilities.”

Dr. Feinstein, however, makes a clear distinction between older MS patients and the use of marijuana by young people whose brains are still developing.

“If you start smoking in your teenage years, and you are a frequent user, by the time you get to your 30s, you can have an array of cognitive deficits.”

Marijuana may also act as a trigger for psychosis, including schizophrenia, in some genetically-susceptible individuals.

“There is reasonably strong data showing this is a bad drug for young people.”

Most experts generally agree it should not be prescribed to children or pregnant women because it could impair normal mental development.

Dr. Bernard Le Foll, a clinician and scientist at the Centre for Addiction and Mental Health in Toronto, points out that smoking dope may also elevate the chances of developing lung cancer and cardiovascular disease – similar to the threat posed by inhaling cigarette smoke.

But the extent of this risk is hard to estimate because people don’t tend to smoke as much marijuana as they do tobacco. “There is some evidence that long-term marijuana use is associated with an increased risk of lung cancer, but the risk is far lower than that associated with cigarette smoking. I suspect it’s partly a matter of dose. Find me someone who smokes 30 or 40 joints a day. It’s very hard to do. Not so with cigarettes. ” says Dr. Juurlink.

Smoking hazards can be minimized by eating the dope or vaporizing it. Patients also have the option of using the existing cannabinoid pharmaceutical products, although many seem to prefer smoking cannabis.

Overall, Dr. Juurlink believes medical marijuana needs to be judged in the context of conventional drugs that often carry significant risks as well.

“I don’t see people dying of cannabis,” he says, “but I do see people suffering harm and dying from, for example, other more conventional treatments for pain , including too much acetaminophen, non-steroidal anti-inflammatory drugs and opioids.

Dr. Juurlink has talked with numerous patients who didn’t benefit from traditional therapy but felt better with a puff on a joint – either they were less anxious, or experience better pain relief. In those cases, he is inclined to prescribe marijuana instead of the standard pharmaceuticals.

“I am very much in favour of more and better evidence regarding the risks and benefits of marijuana. However, to forgo something a patient has told you works for them – that is, it genuinely makes them feel better – and opt for something that may not work as well or may carry even greater risks, frankly, I think that’s close-minded

With the new federal marijuana regulations taking effect shortly, more patients like you may be asking their doctors to write them prescriptions.

Additional high-quality research is certainly needed to clarify its most appropriate uses. At least now the pace of study appears to be increasing along with the growing demand for medical cannabis.


About the author

Paul Taylor

Paul Taylor retired from his role as Sunnybrook's Patient Navigation Advisor in 2020. From 2013 to 2020, he wrote a regular column in which he provided advice and answered questions from patients and their families. Follow Paul on Twitter @epaultaylor


  • I have Rheumatoid Arthritis and pain full Spinal Stenosis. Since I cannot handle acetaminophen and my pain increases with aspirin I have had to rely on Gabapen and herbal anti-inflammatory medication. I immagine Marahuana belongs in the herbal catagory; however for reasons I can only guess the medical doctors have little if any knowledge of vitamins and herbs that may help in cases like myself. So what I have had to do is use myself as a ginnypig and experiment on myself to find my own relief. It is very frustrating for me when I go to a physician who has no answers and poo-poos my personal quest through the herbal jungle to find answers. I have no idea as to what side effects this journey is having on my deteriorating body; but onward I stumble. If there are any answers other than surgery which also may not work, and I do do physio: I sure as hell am waiting for some clear intelligent response.

  • I suffer from small fibre peripheral neuropathy. I have been prescribed MM for my condition. I have read that scientific peer reviewed papers have found that cannabis used in conjunction with traditional chemotherapy works far better than chemotherapy alone. Other peer reviewed scientific papers have found that cannabis creates apoptosis in cancer cells on its own. Other peer reviewed studies have found that chemotherapy does reach all the cancer cells because of restrictions that are formed in our blood vessels. Cannabis has been shown to relax and thereby eliminate the restriction in the blood vessels. Lastly, chronic inflammation triggers malignancy. Cannabis is considered the best natural anti inflammatory agent. According to my family history, I had a better than average chance of developing a malignancy by now. Perhaps the cannabis I take for my small fibre peripheral neuropathy has also served to prolong my life. There are no pharmaceutical companies interested in funding such research. With no funding, who will pay for the research to test the studies that have been published?

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