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Addictions

Four new studies show link between heavy cannabis use, serious health risks

Published

6 months ago

8 minute read

Cannabis products purchased in Ontario and B.C., including gummies, pre-rolled joints, chocolates and dried flower; April 11, 2025. [Photo credit: Alexandra Keeler]

By Alexandra Keeler

New Canadian research shows a connection between heavy cannabis use and dementia, heart attacks, schizophrenia and even death

Six months ago, doctors in Boston began noticing a concerning trend: young patients were showing up in emergency rooms with atypical symptoms and being diagnosed with heart attacks.

“The link between them was that they were heavy cannabis users,” Dr. Ahmed Mahmoud, a cardiovascular researcher and physician in Boston, told Canadian Affairs in an interview.

These frontline observations mirror emerging evidence by Canadian researchers showing heavy cannabis use is associated with significant adverse health impacts, including heart attacks, schizophrenia and dementia.

Sources warn public health measures are not keeping pace with rapid changes to cannabis products as the market is commercialized.

“The irony of this moment is that society’s risk perception of cannabis is at an all-time low, at the exact moment that the substance is probably having increasingly negative health impacts,” said Dr. Daniel Myran, a physician and Canada Research Chair at the University of Ottawa. Myran was lead researcher on three new Canadian studies on cannabis’ negative health impacts.

Legalization

Canada was the first G7 country to create a commercial cannabis market when it legalized the production and sale of cannabis in 2018.

The drug is now widely used in Canada.

In the 2024 Canadian Cannabis Survey, an annual government survey of cannabis trends, 26 per cent of respondents said they used cannabis for non-medical purposes in the past year, up from 22 per cent in 2018. Among youth, that number was 41 per cent.

Health Canada’s website warns that cannabis use can lower blood pressure and raise heart rates, which can increase the risk of a heart attack. But the warnings on cannabis product labels vary. Some mention risks of anxiety or effects on memory and concentration, but make no mention of cardiovascular risks.

The annual cannabis survey also shows a significant percentage of Canadians remain unaware of cannabis’ health risks.

In the survey, only 70 per cent of respondents said they had enough reliable information to make informed decisions about cannabis use. And 50 per cent of respondents said they had not seen any education campaigns or public health messages about cannabis.

At the same time, researchers are finding mounting evidence that cannabis use is associated with health risks.

A 2023 study by researchers at the University of Calgary, the University of Alberta and Alberta Health Services found that adults with cannabis use disorder faced a 60 per cent higher risk of experiencing adverse cardiovascular events — including heart attacks. Cannabis use disorder is marked by the inability to stop using cannabis despite negative consequences, such as work, social, legal or health issues.

Between February and April of this year, three other Canadian studies linked frequent cannabis use to elevated risks of developing schizophrenia, dementia and mortality. These studies were primarily conducted by researchers at the Ottawa Hospital Research Institute and ICES uOttawa (formerly the Institute for Clinical Evaluative Sciences).

“These results suggest that individuals who require hospital-based care for a [cannabis use disorder] may be at increased risk of premature death,” said the study linking cannabis-related hospital visits with increased mortality rates.

The three 2024 studies all examined the impacts of severe cannabis use, suggesting more moderate users may face lower risks. The researchers also cautioned that their research shows a correlation between heavy cannabis use and adverse health effects, but does not establish causality.

 

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Budtenders

Health experts say they are troubled by the widespread perception that cannabis is entirely benign.

“It has some benefits, it has some side effects,” said Mahmoud, the Boston cardiovascular researcher. “We need to raise awareness about the side effects as well as the benefits.”

Some also expressed concern that the commercialization of cannabis products in Canada has created a race to produce products with elevated levels of THC, the main psychoactive compound that produces a “high.”

THC levels have more than doubled since legalization, yet even products with high THC levels are marketed as harmless.

“The products that are on the market are evolving in ways that are concerning,” Myran said. “Higher THC products are associated with considerably more risk.”

Myran views cannabis decriminalization as a public health success, because it keeps young people out of the criminal justice system and reduces inequities faced by Indigenous and racialized groups.

“[But] I do not think that you need to create a commercial cannabis market or industry in order to achieve those public health benefits,” he said.

Since decriminalization, the provinces have taken different approaches to regulating cannabis. But even in provinces where governments control cannabis distribution, such as New Brunswick and Nova Scotia, products with high THC levels dominate retail shelves and online storefronts.

In Myran’s view, federal and provincial governments should instead be focused on curbing harmful use patterns, rather than promoting cannabis sales.

Ian Culbert, executive director of the Canadian Public Health Association, thinks governments’ financial interest in the cannabis industry creates a conflict of interest.

“[As with] all regulated substances, governments are addicted to the revenue they create,” he said. “But they also have a responsibility to safeguard the well-being of citizens.”

Culbert believes cannabis retailers should be required to educate customers about health risks — just as bartenders are required to undergo Smart Serve training and lottery corporations are required to mitigate risks of gambling addiction.

“Give ‘budtenders’ the training around potential health risks,” he said.

“While cannabis may not be the cause of some of these negative health events … it is the intersection at which an intervention can take place through the transaction of sales. So is there something we can do there that can change the trajectory of a person’s life?”

This article was produced through the Breaking Needles Fellowship Program, which provided a grant to Canadian Affairs, a digital media outlet, to fund journalism exploring addiction and crime in Canada. Articles produced through the Fellowship are co-published by Break The Needle and Canadian Affairs.

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Addictions

BC premier admits decriminalizing drugs was ‘not the right policy’

Published on October 16, 2025

By

From LifeSiteNews

By Anthony Murdoch

Premier David Eby acknowledged that British Columbia’s liberal policy on hard drugs ‘became was a permissive structure that … resulted in really unhappy consequences.’

The Premier of Canada’s most drug-permissive province admitted that allowing the decriminalization of hard drugs in British Columbia via a federal pilot program was a mistake.

Speaking at a luncheon organized by the Urban Development Institute last week in Vancouver, British Columbia, Premier David Eby said, “I was wrong … it was not the right policy.”

Eby said that allowing hard drug users not to be fined for possession was “not the right policy.

“What it became was a permissive structure that … resulted in really unhappy consequences,” he noted, as captured by Western Standard’s Jarryd Jäger.

LifeSiteNews reported that the British Columbia government decided to stop a so-called “safe supply” free drug program in light of a report revealing many of the hard drugs distributed via pharmacies were resold on the black market.

Last year, the Liberal government was forced to end a three-year drug decriminalizing experiment, the brainchild of former Prime Minister Justin Trudeau’s government, in British Columbia that allowed people to have small amounts of cocaine and other hard drugs. However, public complaints about social disorder went through the roof during the experiment.

This is not the first time that Eby has admitted he was wrong.

Trudeau’s loose drug initiatives were deemed such a disaster in British Columbia that Eby’s government asked Trudeau to re-criminalize narcotic use in public spaces, a request that was granted.

Records show that the Liberal government has spent approximately $820 million from 2017 to 2022 on its Canadian Drugs and Substances Strategy. However, even Canada’s own Department of Health in a 2023 report admitted that the Liberals’ drug program only had “minimal” results.

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Addictions

Canada must make public order a priority again

Published on October 2, 2025

By

A Toronto park

Public disorder has cities crying out for help. The solution cannot simply be to expand our public institutions’ crisis services

[This editorial was originally published by Canadian Affairs and has been republished with permission]

This week, Canada’s largest public transit system, the Toronto Transit Commission, announced it would be stationing crisis worker teams directly on subway platforms to improve public safety.

Last week, Canada’s largest library, the Toronto Public Library, announced it would be increasing the number of branches that offer crisis and social support services. This builds on a 2023 pilot project between the library and Toronto’s Gerstein Crisis Centre to service people experiencing mental health, substance abuse and other issues.

The move “only made sense,” Amanda French, the manager of social development at Toronto Public Library, told CBC.

Does it, though?

Over the past decade, public institutions — our libraries, parks, transit systems, hospitals and city centres — have steadily increased the resources they devote to servicing the homeless, mentally ill and drug addicted. In many cases, this has come at the expense of serving the groups these spaces were intended to serve.

For some communities, it is all becoming too much.

Recently, some cities have taken the extraordinary step of calling states of emergency over the public disorder in their communities. This September, both Barrie, Ont. and Smithers, B.C. did so, citing the public disorder caused by open drug use, encampments, theft and violence.

In June, Williams Lake, B.C., did the same. It was planning to “bring in an 11 p.m. curfew and was exploring involuntary detention when the province directed an expert task force to enter the city,” The Globe and Mail reported last week.

These cries for help — which Canadian Affairs has also reported on in Toronto, Ottawa and Nanaimo — must be taken seriously. The solution cannot simply be more of the same — to further expand public institutions’ crisis services while neglecting their core purposes and clientele.

Canada must make public order a priority again.

Without public order, Canadians will increasingly cease to patronize the public institutions that make communities welcoming and vibrant. Businesses will increasingly close up shop in city centres. This will accelerate community decline, creating a vicious downward spiral.

We do not pretend to have the answers for how best to restore public order while also addressing the very real needs of individuals struggling with homelessness, mental illness and addiction.

But we can offer a few observations.

First, Canadians must be willing to critically examine our policies.

Harm-reduction policies — which correlate with the rise of public disorder — should be at the top of the list.

The aim of these policies is to reduce the harms associated with drug use, such as overdose or infection. They were intended to be introduced alongside investments in other social supports, such as recovery.

But unlike Portugal, which prioritized treatment alongside harm reduction, Canada failed to make these investments. For this and other reasons, many experts now say our harm-reduction policies are not working.

“Many of my addiction medicine colleagues have stopped prescribing ‘safe supply’ hydromorphone to their patients because of the high rates of diversion … and lack of efficacy in stabilizing the substance use disorder (sometimes worsening it),” Dr. Launette Rieb, a clinical associate professor at the University of British Columbia and addiction medicine specialist recently told Canadian Affairs.

Yet, despite such damning claims, some Canadians remain closed to the possibility that these policies may need to change. Worse, some foster a climate that penalizes dissent.

“Many doctors who initially supported ‘safe supply’ no longer provide it but do not wish to talk about it publicly for fear of reprisals,” Rieb said.

Second, Canadians must look abroad — well beyond the United States — for policy alternatives.

As The Globe and Mail reported in August, Canada and the U.S. have been far harder hit by the drug crisis than European countries.

The article points to a host of potential factors, spanning everything from doctors’ prescribing practices to drug trade flows to drug laws and enforcement.

For example, unlike Canada, most of Europe has not legalized cannabis, the article says. European countries also enforce their drug laws more rigorously.

“According to the UN, Europe arrests, prosecutes and convicts people for drug-related offences at a much higher rate than that of the Americas,” it says.

Addiction treatment rates also vary.

“According to the latest data from the UN, 28 per cent of people with drug use disorders in Europe received treatment. In contrast, only 9 per cent of those with drug use disorders in the Americas received treatment.”

And then there is harm reduction. No other country went “whole hog” on harm reduction the way Canada did, one professor told The Globe.

If we want public order, we should look to the countries that are orderly and identify what makes them different — in a good way.

There is no shame in copying good policies. There should be shame in sticking with failed ones due to ideology.

 

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consider getting a voluntary paid subscription.

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