Weeding Out Stigma and Cultivating Evidence


Weeding Out Stigma and Cultivating Evidence

When Vincent Maida began prescribing medical cannabis to his patients in Toronto 20 years ago, he was pioneering a treatment option that was not widely accepted in the medical community. What piqued his interest was hearing the narratives of his patients - people with cancer, multiple sclerosis, and chronic pain - who continued to suffer despite using standard guideline medications.

“They took things into their own hands, using recreational cannabis, and told me they got better. They had a better quality of life and were able to continue on with their chemo and radiation therapies. I took what they told me at face value. I was regarded as a heretic, a weirdo, a quasi-quack, but I saw the results and I carried on.”

Maida has noticed more openness and acceptance from his peers in the past few years. Significantly, he delivered the keynote address to the Canadian Association of Medical Oncologists (CAMO) annual scientific meeting in Toronto on April 26. “I find it remarkable for a palliative medicine physician to be chosen to give the keynote at a national oncology organization’s annual meeting,” he said. “It really shows that the tide is turning toward acceptance.”

Maida has called Toronto home his whole life. He received his BSc and MD from the University of Toronto, as well as an MSc with a specialty in wound management. He has worked for 35 years at Etobicoke General Hospital, where he is a palliative medicine specialist and is active in clinical research that focuses on pain, symptom management, and wound treatment.

When he started his palliative medicine career, Dr. Maida attended international conferences where he heard influential people talk about cannabis therapies, including Robert Twycross (Oxford University), a pioneer of the hospice movement.

“It validated the whole area for me in the early days, prior to medical legalization,” he said. “When the pharmaceutical cannabinoids came along (e.g., dronabinol and nabilone), I started prescribing them.”

He went on to publish a prospective observational study of nabilone (Maida et al. 2008), which was the first account of cannabinoids being associated with opioid sparing, a topic that is of primary importance these days. The study suggested that the use of pharmaceutical cannabinoids was associated, not only with better pain and symptom management, but also with reduced reliance on opioids and other medications.

Lack of clinical trials does not equate with lack of evidence


“It surprises me that many doctors continue to say there’s a void of evidence to support the use of medical cannabis as a treatment option,” he said. “Medical school trains people to only think in a certain way. Randomized controlled studies, randomized controlled studies, randomized controlled studies. Lack of that type of evidence is not the same as lack of efficacy. The greatest testament to evidence-based medicine is the test of time. Cannabinoids have been around for thousands of years, used by ancient cultures for all sorts of maladies. These things work.”


He believes that, after almost a century of prohibition, we are just beginning to accumulate the type of evidence that will convince those who insist on the standard, contemporary level of proof. “In the meantime, they’re not doing their patients any favours - in fact they’re doing them a disservice and an injustice - by taking that stance.”

The value of anecdotal evidence

A common criticism among skeptics is the reliance on anecdotal evidence for the benefits of medical cannabis. Maida, in contrast, sees value in many sources of data, not just randomized controlled trials.

“Patient reports are still the most reliable source of data,” Maida said. “Everything starts out with an anecdote. We can collect multiple anecdotes, then look into it in more detail. Physicians and scientists are starting to realize that evidence-based medicine has its deficiencies and doesn’t always reflect the real world.”

For example, Maida refers to what he considers to be a major limitation of randomized controlled studies: the limited nature of their test subjects. “Evidence-based medicine is not perfect unless you use cohorts. To translate the evidence from a randomized controlled study in a perfect way, you would only prescribe to the types of people who are identical to those in the study. Take cholesterol-lowering medications, known to be effective at reducing heart attack and stroke. The study populations have been people in their 30s, 40s, and 50s. There isn’t RCT evidence that an 80-year old should be on them. But they’re still prescribed to the elderly.”

“Medical Cannabis - Weeding out stigma and cultivating evidence”

Maida’s CAMO conference keynote address touched on the endocannabinoid system, the potential for cannabinoid therapies for pain and symptom management in oncologic supportive care, and also identified the range of cannabinoid therapies and routes of administration. He relied on published studies, pointing primarily to a recent review of the current evidence undertaken by the National Academies of Sciences, Engineering, and Medicine (2017). This review looked at more than 10,000 peer-reviewed articles and concluded that there is substantial or conclusive evidence for the use of medical cannabis to treat chronic pain, chemotherapy-induced nausea and vomiting (CINV), and muscle spasticity in patients with MS.

“This evidence includes the most recent meta-analyses of 10 randomized controlled trials with pharmaceutical cannabinoids and 6 RCTs with medical cannabis. The NASEM meta-analysis confirms my anecdotal experience with pain and CINV.”

When a patient gets diagnosed with cancer, the goals of care evolve from attempting to cure, to prolonging life, and, finally, to palliative care that allows for a natural, peaceful death. Maida uses medical cannabis across this continuum of care with his patients.

“Cannabis should be integrated into practice from day one of diagnosis, not just for pain and symptom management,” he said. “It’s a shame to wait until someone is terminally ill when there’s so much evidence to incorporate cannabinoid-based medicine in treatment. They’re going to have better pain relief and symptom management, and they’re going to tolerate their oncology treatments better. We’re improving quality of life and perhaps length of life without any negative sequelae, other than the cost of cannabis medicine.”

The need for ongoing medical advice post-legalization

Maida firmly adheres to the necessity of maintaining the medical stream even after recreational cannabis becomes legal in Canada later this year.

“Definitely, absolutely, medical should be distinct from the recreational stream. We need to encourage patients to go to their physicians, instead of self-medicating.” He worried that patients won’t want to go to a clinic or a doctor’s office and they’ll experiment with limited information. “They’ll buy the wrong stuff, they’ll have a bad reaction, and they will think it has no benefit.”

Maida feels that healthcare professionals can and should be learning about medical cannabis and get comfortable authorizing themselves since they know their patients best. “If an oncologist has a patient who needs cannabinoids, the oncologist should be the one to prescribe. If a neurologist has accountability, they should prescribe.”

For more than 20 years, Maida has seen the benefits of medical cannabis treatment in his clinical practice, and encourages oncologists to consider cannabinoids for every patient, early on.

“Cannabinoids should not be an afterthought after standard treatments. They should use it right from the kickoff of the oncology journey.

“My wish is that cannabinoid therapies can be integrated into oncology at the beginning of the patient’s journey, not as a Hail Mary pass out of desperation at the end-stage.”


Maida V, Ennis M, Irani S, et al. 2008. Adjunctive nabilone in cancer pain and symptom management: a prospective observational study using propensity scoring. J Support Onc. 6(3):119-124.

National Academies of Sciences, Engineering, and Medicine. 2017. The health effects of cannabis and cannabinoids: Current state of evidence and recommendations for research. Washington, DC: The National Academies Press. http://nationalacademies.org/hmd/
reports/2017/health-effects-of-cannabis-and-cannabinoids.aspx. Published 2017. Accessed November 24, 2017.