Medical benefits from cannabis? Still waiting for proof

Weed your way through websites selling cannabis products and you’ll likely be told that the drug is bringing desperately needed relief to people suffering from chronic pain, arthritis and many other ailments.

Just don’t expect to find the clinical evidence to back that up.

Four years after legalizing cannabis, the federal government’s clinical trial database at Health Canada shows little sign of active research to evaluate the alleged medicinal benefits of the drug. The absence frustrates many researchers, who contend that the cultivators, processors, and sellers of cannabis in Canada have little incentive to fund rigorous pharmaceutical analyses of their claims.

Instead, researchers say, the industry is content instead to sell their products under less stringent requirements needed to serve the recreational market.

“Cannabis growers are not interested in supporting medical access,” says Mary-Ann Fitzcharles, associate professor of medicine at McGill University and a leading pain researcher, adding that early hopes for partnerships between industry and researchers to conduct the proper studies have fizzled.

That absence of data leaves patients seeking help for their ailments – and their doctors – in the dark about the accuracy of claims made by cannabis companies and some patient advocacy groups. Studies quoted by cannabis companies to support their claims are not clinical trials and mostly include patient surveys and observational studies often conducted by the companies which can lead to considerable bias. About 400,000 Canadians currently have medical cannabis authorizations from their doctors, with many more widely believed to be using the drug medicinally.

But data on its effectiveness or potential harm does not yet exist.

The research community cites several reasons for the failure. When cannabis was legalized in Canada in 2018, this opened the door for collaborations with researchers and industry to finally test the medicinal properties of cannabis using the gold standard in testing drugs – clinical trials. However, cannabis is classified as a drug under the Food and Drugs Act and therefore must follow Health Canada’s Good Manufacturing Practices to ensure it consistently meets quality standards. This research gauntlet is more complicated and expensive for cannabis companies to pursue than the less-resistant path to getting approval for recreational markets. Even if a researcher wanted to buy cannabis legally from a local supplier and test it, they would still need to go “back to the beginning,” and complete many more studies to successfully develop a clinical trial application with Health Canada for the specific form of cannabis

Researchers also note that studies can be hampered by complexities in the ingredients making up cannabis products, notably the widely varying amounts of tetrahydrocannabinol (THC), the chemical that can make users feel high.

But they also blame Health Canada for failing to proactively streamline the clinical trial process for cannabis while still assuring quality standards. Last year, more than 200 clinicians and scientists wrote an open letter to Health Canada demanding revisions to the current regulatory process.

So far, there has been little movement on the regulatory front. Some tinkering has made it easier for a handful of researchers to obtain research licenses and approval to start conducting cannabis studies in certain situations, for example when there is adequate safety data for humans.

But that falls short of the prioritization for cannabis studies that researchers say they need as most candidate cannabis products are still required to have in-depth pre-clinical and safety studies.

So far, there has been little movement on the regulatory front.

“A separate pathway for prescription cannabis products is not being considered at this time,” says Tammy Jarbeau, senior media relations advisor for Health Canada. A mandated review of the Cannabis Act that was expected to begin in October 2021 is planned shortly, Jarbeau says. It is unclear if this review will focus on ways to improve the regulatory process for cannabis studies with Health Canada.

The sluggish government response is discouraging, says James MacKillop, Professor of Psychiatry and Behavioural Neuroscience and Director of the Michael G. DeGroote Centre for Medicinal Cannabis Research at McMaster University.

“What I would have loved to see would have been permitting products that are legally available for sale and consumption for Canadians to be evaluated for their therapeutic purposes,” says MacKillop. “Why would you not create a path for the products that Canadians are consuming to be evaluated for whether they work or not?”

Cannabis companies contend they share the frustration at the way studies are conducted in Canada. Some, like Ontario-based Canopy Growth Corporation, say they are conducting trials in other countries, including in more recent years the U.S. where federal laws like the U.S. Farm Bill make it easier for academic institutions to run studies on the medical effects of cannabis.

But the industry acknowledges that strong financial headwinds in the cannabis sector that have driven some companies out of business and others into life-saving mergers have diverted attention and resources from clinical research slowing the accumulation of good evidence.

“Companies like Canopy have to make decisions on priorities – where to invest their money and where to put their energy,” says Mark Ware, Chief Medical Officer of Canopy Growth Corporation previously with McGill University, where he was a long-time researcher. Like other companies in the sector in Canada, he says, Canopy has focused more on the business side rather than conducting medical research.

“At the same time that we were struggling with these issues, the company was undergoing some reorganizations and redefining strategies; the idea of pursuing pharmaceutical products was not a priority at that time,” says Ware.

Patients won’t get clear answers from advocacy organizations either. Information about cannabis on the Arthritis Society website is sponsored by companies like Spectrum Therapeutics, a pharmaceutical company owned by Canopy Growth. Spectrum’s own website says it is delivering “medical cannabis products to improve the lives of patients around the world.”

The Arthritis Society’s site devotes several pages to the uses of medical cannabis in controlling pain, presenting information on everything from how to access it to online webinars by physicians – sponsored by cannabis growers such as Harvest Medicine and Cana Farms.

The gap in good evidence is not lost on Sian Bevan, Chief Science Officer of the Arthritis Society. She notes that the Arthritis Society is funding cannabis research to fill the void but in the meanwhile it needs to help the many Canadians who are already using medical cannabis for pain.

“People want to understand what we know and what we don’t know and we can provide that platform for people coming to us for information,” Bevan says.

Researchers stress that the uncertainty can only be cured by the good data that comes from clinical trials.

“It seems like we should be doing our darndest to evaluate benefits and harms,” says MacKillop.

The comments section is closed.


Stephanie Keeling


Stephanie Keeling is a rheumatologist and Professor of Medicine at the University of Alberta. She is currently a participant in the Certificate in Health Impact program at the Dalla Lana School of Public Health, University of Toronto

Republish this article

Republish this article on your website under the creative commons licence.

Learn more