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Canada’s decision to legalize cannabis four years ago underpinned the expectation that the country would become a global leader of research into areas ranging from the drug’s usefulness for pain mitigation to its possible links to mental illness.Sean Kilpatrick/The Canadian Press

The month Canadians first flocked to buy legal cannabis, Jason Busse and a team at McMaster University sent in their application for a coveted federal research grant and soon became one of just a handful of groups given this funding to conduct clinical trials on the drug. That was in October, 2018.

Four years on, Dr. Busse let out an exasperated chuckle when asked what his team has learned about how cannabidiol (CBD) pills help knee-replacement patients with their pre- and post-op pain.

He said he hopes to begin recruiting for the 50-person trial this month.

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Dr. Busse, associate director of McMaster’s Michael G. DeGroote Centre for Medicinal Cannabis Research, said the biggest delay was because Ottawa required researchers to source cannabis products made to a pharmaceutical grade that most growers can’t meet – and don’t have to in the recreational market.

“We initially met with over 50 licensed producers and none of them could provide a product Health Canada would accept,” he said.

His team’s protracted struggles parallel the plight of many medical researchers who told The Globe and Mail they are only now overcoming bureaucratic hurdles to begin testing how cannabis may help or harm humans.

Meanwhile, social scientists and epidemiologists who spoke with The Globe say the pandemic has vastly altered everyday life, adding significant “noise” to their data and delaying their work into seeing how society has changed since legalization.

A year and a half after getting the cannabis grant, Dr. Busse’s team and eight other groups joined a round table by the Canadian Institutes of Health Research to update the government-funded agency on their progress.

Dr. Busse piped up first to say they hadn’t even been able to secure Health Canada’s approval of the cannabis they wanted to use. He wasn’t alone.

“As soon as I said that every other investigator on the phone said, ‘Us too,’ ” he said.

Canada’s decision to legalize cannabis four years ago underpinned the expectation that the country would become a global leader of research into areas ranging from the drug’s usefulness for pain mitigation to its possible links to mental illness. Comparing 10 provinces, each with a different way to implement legalization, gives researchers a rare opportunity to see how this massive shift in public policy has affected Canadians across the country.

But the initial high hopes that legalization would boost research into a plant long rejected and restricted by the scientific establishment have now been tempered, with Health Canada statistics indicating a downturn in cannabis science since then.

In 2019, Health Canada handed out 209 licences to individual scientists, academic and research institutions, and corporations. The federal department has steadily granted fewer licences each year since, with 79 being approved so far this year, according to a recent statement e-mailed by spokesperson Tammy Jarbeau.

The agency is aware that researchers have faced challenges in conducting studies with cannabis products available in Canada’s legal market, given the higher-grade cannabis Health Canada requires for clinical trials, she said. The agency is now reviewing whether to cut out the detailed clinical trial rules for researchers tackling the harms of cannabis, such as how it impairs drivers.

“Health Canada recognizes that conducting clinical research (i.e., research carried out on humans) with cannabis is critical to generating high-quality evidence that can be used to better understand the health risks and benefits of cannabis use, inform health policies and protect the health and safety of Canadians,” Ms. Jarbeau’s statement said.

Despite the challenges, there have been some early, useful results from the original influx of funding.

Sussing out the society-wide effects of legalization is still years away on many issues, but official data have so far shown that Canada has been relatively successful at the federal government’s core goals of displacing the illicit market and keeping the drug out of the hands of young people, according to many of the academics interviewed by The Globe. That’s despite the legal cannabis industry’s loud criticisms of Ottawa’s regulatory regime, they added.

Many of the experts surveyed pointed to a recent New England Journal of Medicine study of motor vehicle collisions on Canada’s West Coast between 2013 and 2020 that showed the number of injured drivers arriving in several hospital emergency rooms with levels of tetrahydrocannabinol (THC) – the main psychoactive compound in cannabis – above the legal driving limit of two nanograms/ml more than doubled. The January study, led by Jeff Brubacher, a UBC scientist who leads the emergency room research program at Vancouver General Hospital, found older people and men registered the largest increase in this impairment behind the wheel.

Many more directed The Globe to another study in the New England Journal of Medicine, published this summer, which suggested that restricting the sale of edibles helped Quebec minimize harms to kids. The study, led by Daniel Myran, a health services researcher at the University of Ottawa, found the rate of children being hospitalized for consuming cannabis was three times higher than before legalization in Quebec, but 7½ times higher in Alberta, B.C. and Ontario after edible products began rolling out in those provinces in 2020. (From January, 2020, to September, 2021, Quebec had 44 of these poisonings compared to 312 across the three other provinces over that span, according to the study.)

Robert Gabrys, a senior research and policy analyst at the Canadian Centre on Substance Use and Addiction, said the study funded by the centre shows that provinces allowing more liberal cannabis markets also run the risk of higher overall consumption and its attendant risks.

Dr. Gabrys, whose organization has allocated $10-million to different cannabis research projects over the first five years of legalization, said an area that needs much more study is how to improve the general public’s understanding of the potency of cannabis and the myriad products on the market.

“As an example, most people don’t know what a high or low THC level is,” he said.

Candice Crocker, a neuroscientist and assistant professor at Dalhousie University, is researching why some people who use cannabis end up in the emergency room and others don’t. Her interviews had to be suspended in April, 2020, when the first wave of the pandemic made them impossible to do.

But one early takeaway from her continuing study is that most of the people hospitalized for cannabis consumption don’t link their medical emergency to the drug when interviewed a week later, she said.

That may be unsurprising, given most Canadians still think cannabis is relatively harmless, Dr. Crocker said. Plus, she added, scientists don’t know enough yet to be able to predict who may have trouble with cannabis and should stay away – a risk factor for the drug, she said, may one day be likened to how people with family histories of alcoholism are cautioned to abstain or drink very little.

“If I go to a cocktail party and someone finds out that I’m doing cannabis research I get an earful about how harmless it is and ‘Why am I doing this?’ ” said Dr. Crocker, who added that many East Coasters often have more positive views of the drug compared to their compatriots.

Studies have shown that cannabis increases one’s risk for psychosis, she said, particularly in those under 25. In her talks with high school students, Dr. Crocker doesn’t preach abstinence but tells the teens that if they ever have a bad trip with cannabis then they should stay away from it.

David Hammond, a professor at the School of Public Health Sciences at the University of Waterloo who had previously spent 25 years studying the impact of tobacco, noted that Quebec has created the strongest rules and regulations and seen the fewest changes in usage among its population, including young people.

“For folks out there asking, ‘Can we legalize and not have everything blow up in terms of kids using?’ Yes, they’ve largely achieved that in Quebec,” Dr. Hammond said.

He says a crucial question that remains unanswered is how many retail outlets communities need to displace the illicit market but sidestep a rise in use of the drug.

While official sales data are good on a national level, he said, most provinces have been very lax in monitoring use within their boundaries so basic questions about who is consuming what and why remain unanswered.

Akwasi Owusu-Bempah, a faculty member in the University of Toronto’s Department of Sociology and director of research for the Cannabis Amnesty non-profit, said legalization has drastically reduced the number of people arrested after getting caught holding illegal products.

That is a positive for Black and Indigenous people, who have long been targeted disproportionately by police officers for this offence, Dr. Owusu-Bempah said. But, he added, some of his preliminary research shows racial disparities have persisted in the smaller number of people getting arrested in the past four years.

Ottawa and the provinces have only recently begun factoring race into their data from myriad health and social programs, so figuring out how legalization has harmed or benefited members of different racial and ethnic groups is going to be very difficult.

“We won’t have robust prelegalization data with which to draw comparisons,” Dr. Owusu-Bempah said.

The latest official data show that, as of July, Canadians bought more than $2.5-billion worth of recreational cannabis at a licensed retailers to date this year.

These sales data will be key to analyzing population-level trends over the next decade, Dr. Hammond said, but he and his colleagues worry that research on cannabis will continue to dwindle without Ottawa mandating that some of the millions in cannabis tax revenue each year go toward more studies.

Dr. Busse, the knee-pain researcher from McMaster, said he is still struck by how the plant and its permutations vex regulators. For example, he said, researchers with his upcoming study of knee-replacement patients had initially wanted to store the cannabis at the hospital pharmacy, but the pharmacist said the bureaucratic red tape would be too much. So, Dr. Busse said, his team eventually found a small room in the hospital with a special lock and cameras that they are hoping will soon get final approval from Health Canada.

“We’re just looking at CBD,” he said. “It’s non-psychotropic and it’s still considered in the same category, essentially, as opioids.”