Pot's potential benefit for mental health among understudied areas that could be new research priorities

Calgary researchers who examined more than 1,000 studies of cannabis and mental health say only two looked at possible benefits instead of harm — and overall there are some big gaps in knowledge that could become national research priorities.

University of Calgary researchers looked at more than 1,000 studies about cannabis and mental health

Only two of more than 1,000 studies about cannabis and mental health looked at possible benefits. (Jane Robertson/CBC)

Calgary researchers who examined more than 1,000 studies of cannabis and mental health say only two looked at possible benefits instead of harm — and overall there are some big gaps in knowledge that could become national research priorities.

The new report, Cannabis and Mental Health: Priorities for research in Canada, was created by researchers at the University of Calgary to close the gap on cannabis and mental health research.

Following legalization in October 2018, the Mental Health Commission of Canada was asked by Health Canada and the federal government to lead the research agenda and conversation around cannabis and mental health in Canada.

The commission in turn asked the University of Calgary to put together a report that looked at the scope of cannabis and mental health research to identify what is known, what is unknown and what areas should be the focus of future research. 

"They realize one of the things that they needed to do before they could kind of launch into where we should go from here is really understand where we are now," said Fiona Clement, associate professor in the university's Department of Community Health Sciences and one of the report's lead authors. 

Clement says the research tended to stem from the idea of cannabis being harmful to one's mental health. 

Only two studies evaluated by her team looked at possible benefits. 

"We know about 14 per cent of Canadians use cannabis," she said. "So clearly there is something there that we just haven't understood yet."

One gap they identified was that the majority of the research had been done with unspecified populations. 

"Like adults without any specificity of age ranges, users — in quotation marks — versus non-users, without any specificity of how often someone is using, what kind of product they're using, how they're using it or when they started using it," she said.

Fiona Clement of the University of Calgary says more could be done to measure the impact of factors like users' ages, lfrequency of use and method of ingestion. (Riley Brandt/University of Calgary)

Clement said some of the research outcomes were just mental health issues — without specifying, for example, depression, anxiety or schizophrenia. She says that makes for a lot of unanswered questions.

"We do think that the relationship between cannabis and a specific mental health outcome such as depression would be mediated by the age of the person, when they started smoking, perhaps their cultural contacts, their exposure to negative social determinants of health, the kind of product that they're using and how they're using it," she said.

"And we think that those relationships might be different for different kinds of mental health disorders."

From left, University of Calgary researchers Ruth Leonora Diaz, Dr. Rebecca Haines-Saah, Brenlea Farkas, Dr. Matthew Hill, Dr. Fiona Clement, and Dr. Scott Patten, who worked on the report titled Cannabis and Mental Health Priorities for Research in Canada. (Jade Markus/University of Calgary)

Clement also said the relationship between edible versus smoked cannabis use was another understudied area.

"None of the studies in the over a thousand that we looked at specifically looked at the relationship between edible cannabis use and mental health outcomes and how that may be different from smoked cannabis," she said. 

"The way your body processes when you're smoking versus ingesting it is different. And so perhaps the relationships are different."

The Mental Health Commission says the report lays the foundation to better understand the relationship between cannabis use and mental health.

"The results of this report will help inform and set new research priorities in Canada," said Ed Mantler, vice-president of programs and priorities with the commission. 

They say Canada now has the opportunity to lead the world in cannabis and mental health research. 


Lucie Edwardson


Lucie Edwardson is a reporter with CBC Calgary, currently focused on bringing you stories related to education in Alberta. In 2018 she headed a pop-up bureau in Lethbridge, Alta. Her experience includes newspaper, online, TV and radio. Follow her on Twitter @LucieEdwardson or reach her by email at


To encourage thoughtful and respectful conversations, first and last names will appear with each submission to CBC/Radio-Canada's online communities (except in children and youth-oriented communities). Pseudonyms will no longer be permitted.

By submitting a comment, you accept that CBC has the right to reproduce and publish that comment in whole or in part, in any manner CBC chooses. Please note that CBC does not endorse the opinions expressed in comments. Comments on this story are moderated according to our Submission Guidelines. Comments are welcome while open. We reserve the right to close comments at any time.

Become a CBC Member

Join the conversation  Create account

Already have an account?