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.

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.

• Legalization leaves Canada poised to lead on cannabis research, says minister

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.

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."

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.