Addictions
‘Greening out’: Experts call for THC limits in cannabis products
Experts warn surging THC levels are fuelling growing health risks — and say stronger regulation is urgently needed
More and more cannabis users are ending up in emergency rooms suffering from severe, repeated bouts of vomiting — a condition known as cannabis hyperemesis syndrome.
A new study found that emergency visits for cannabis hyperemesis syndrome increased 13-fold over eight years, accounting for more than 8,000 of the nearly 13,000 cannabis-related ER visits in that period.
Experts say the mounting health risks associated with cannabis use are due to rising THC levels in cannabis products. They urge stronger regulation, better labeling and more research — using Quebec’s approach as a potential model.
“I don’t think we have the perfect model in Quebec — there’s pros and cons,” said Dr. Didier Jutras-Aswad, a clinical scientist at the Centre hospitalier de l’Université de Montréal (CHUM) and a professor in the Department of Psychiatry and Addiction at Université de Montréal.
“But overall, the process of … progressively implementing changes, not wanting to be the first one in line to put all this new product on the market, I think is probably, in terms of public health, more prudent.”
THC levels
Tetrahydrocannabinol (THC) is the primary psychoactive compound in cannabis and what causes the “high.” It is one of more than 100 cannabinoids, or chemical compounds, naturally found in the cannabis plant.
Delta‑9‑THC is the most common and well-studied form, though other forms of THC exist and are less understood.
Federal drug laws place strict limits on delta-9-THC levels. They cap delta-9-THC at 10 milligrams per piece for edibles, and 1,000 milligrams per container for extracts and topicals. Dried cannabis flower and pre-rolled joints have no THC cap, but must disclose the THC level on their labels.
Other intoxicating cannabinoids — like delta-8-THC — are not regulated the same way. Some producers use these other cannabinoids to get around delta-9 limits to make their products more potent.
In 2023, Health Canada issued guidance warning against this practice, noting it could lead to inspections and regulatory action. Its guidance is not legally binding.
“Good weed”
Dr. Oyedeji Ayonrinde, a professor of psychiatry and psychology at Queen’s University, says “good weed” used to mean a product did not contain pesticides or contaminants. Now, it often means a product is high-THC — reinforcing the risky idea that stronger is better.
“We would say, Oh, man, that guy’s got good weed,’ because it’s 30 per cent [THC],” he said.
Today, THC levels average about 25 per cent — up from about four per cent in the 1960s. But some products go as high as 80 or 90 per cent THC.
“That’s ‘the good stuff,’” said Ayonrinde, referring to how consumers view products with these elevated levels of THC.
“One of the major [health] risk factors is the use of cannabis with higher than 10 per cent THC,” said Dr. Daniel Myran, a physician and Canada Research Chair at the University of Ottawa.
Myran led three Canadian studies this year linking heavy cannabis use to health risks such as schizophrenia, dementia and early death.
Chris Blair, a Canadian originally from Jamaica, says the cannabis he once smoked — natural, Jamaican, homegrown weed known as “sess” — was much milder than what is available through Ontario dispensaries today.
“We grew it, it was natural … the regular Mary Jane sess,” he said. “And then times changed … the sess was pushed to almost become the hydro[ponic] type of thing.”
Hydroponic growing methods produce more potent cannabis with higher THC levels. Blair says he could no longer go back to Jamaican sess, because he had built up a tolerance to it.
“Unfortunately, going back to sess was not the same, because it wasn’t the same high or same strength,” he said.
“Back when [I was] smoking [Jamaican sess] … I’d finished that spliff and we were ready to go hang out, we’re ready to party.
“Nowadays, after you smoke you’re mashed and you’re not doing anything.”
Greening out
Ayonrinde says higher THC levels can alter how the brain’s dopamine receptors work, which may induce paranoia.
“Being out of touch with reality, auditory hallucinogens, delusional thoughts, disorganized thinking — that’s part of the mechanism pathway for the development of a severe and enduring mental illness [like] schizophrenia,” he said.
High THC can also worsen anxiety, disrupt sleep, affect mood and trigger psychosis, he says. Other experts cited risks including cannabis use disorder, mental health issues, and dizziness or nausea — sometimes referred to as “greening out.”
Young people, whose brains are still developing until age 25, are most vulnerable to these harmful effects, Ayonrinde says.
During adolescence, the brain undergoes intense growth. “Think of the brain like a construction site,” he said. Frequent, high-dose THC use during this critical period can disrupt dopamine systems and increase the risk of building scaffolding for serious mental health conditions.
While some literature suggests that cannabidiol (CBD) — another major cannabinoid in most cannabis products — may act as a calming, non-psychoactive counterbalance to THC, Ayonrinde says this is only true at extremely high doses, around 6,000 mg.
Standard measurement
Experts say the diversity of cannabis products on the market is part of the challenge.
“When people say, ‘Weed helps me with my trauma,’ an example I often give is: cannabis is just like saying ‘dog’,” said Ayonrinde.
“What breed? Is it a chihuahua or a rottweiler or a great dane? Because without knowing exactly the THC, CBD … what are you talking about?
“There’s no single cannabis.”
Cannabis products lack clear dosage guidelines, and Ayonrinde says marketing messages push consumers to opt for high potency options.
Ruth Ross, a professor of pharmacology and toxicology at the University of Toronto, would like Canada to adopt a standard unit of measurement for THC levels, so consumers could easily understand what one unit means.
“Say a unit was one milligram; they could multiply that up — it’s easy math,” she said.
Myran agrees. “The way we sell alcohol in this country is not set up so that you pay the same amount for a litre of wine as you do for a litre of vodka,” said Myran.
“You have a minimum price per unit of ethanol … and there’s a really compelling reason to price cannabis according to its THC content … [to] financially discourage people from always moving to the highest potency THC products.”
Ross says there is also a need for more current cannabis research. Most cannabis research evaluates the effects of cannabis products with much lower THC levels than those seen on the market today. Long-term health effects can take decades to appear — similar to tobacco.
“Some of [the health harms] might emerge over many, many years, and we don’t know what those will be until data comes in,” she said.
Quebec’s approach
Ross points to Quebec as a unique model in cannabis regulation. It is the only province that caps THC potency and tightly controls how cannabis can be marketed. For example, edibles resembling candy or desserts are prohibited.
Jutras-Aswad, of the Université de Montréal, says overly strict rules can drive some consumers — especially those younger than the province’s legal age of 21 — to the black market.
Still, he says Quebec’s model offers benefits, including greater control over sales and a public health approach focused on harm reduction rather than profit.
Under Quebec’s Cannabis Regulation Act, the Société québécoise du cannabis (SQDC) is the only authorized cannabis retailer in the province.
SQDC employees are trained to offer science-based information, connect consumers with support services and promote safer use.
Researchers in Ontario are now studying how Quebec’s stricter THC limits may be affecting cannabis-related harms compared to other provinces.
“That’s going to be a really interesting within-Canada experiment,” said Ross.
Myran recommends adopting Quebec’s 30 per cent THC caps nationwide.
He also recommends better product labelling requirements and a pricing model that sets a minimum price per unit of THC — to discourage the purchase of high-potency products.
In a 2023 op-ed, Ross argued provinces should fund cannabis research to guide policy and public health.
In it, she notes that Quebec reinvested all $95 million of its 2022 revenue from cannabis sales into prevention and research. By contrast, Ontario set aside just 0.1% of its $170 million in cannabis revenue for a Social Impact Fund that has no clear public health focus.
“Canada can do so much better. We have world experts in cannabis research from coast-to-coast, and we are uniquely positioned to have high-quality, well-funded research on its medical use and potential harms,” she wrote.
“Five years from now, will we be dealing with major public health challenges that could have been avoided?”
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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By Alexandra Keeler
Experts say physicians have lost their ‘zeal’ for prescribing safer supply amid growing concerns about diversion and effectiveness
Participation in B.C.’s safer supply program — which offers prescription opioids to people who use drugs — has dropped by nearly 25 per cent over the past two years, according to recent government data.
The B.C. Ministry of Health says updated prescribing guidelines and tighter program oversight are behind the decline.
But addiction experts say the story is more complicated.
“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),” said Dr. Launette Rieb, a clinical associate professor at the University of British Columbia and addiction medicine specialist.
“Many doctors who initially supported ‘safe supply’ no longer provide it but do not wish to talk about it publicly for fear of reprisals,” she said in her email.
Missing data
B.C. has had safer supply programs in place province-wide since 2021.
Participation in its program peaked at nearly 5,200 individuals in March 2023, and then declined to fewer than 3,900 individuals by December 2024. This is the most recent data publicly available, according to B.C.’s health ministry.
In an emailed statement, the ministry attributed the decline to updated clinical guidance and more restrictive prescribing practices “aimed at strengthening the integrity and safety of the program.”
In February, the province updated its safer supply prescribing guidelines to require most patients of the program to consume prescription opioids under the supervision of health-care professionals — a practice known as “witnessed dosing.”
The B.C. government has not released any data on how many patients have been transitioned to witnessed dosing.
The ministry did not address Canadian Affairs’ questions about whether patients are being cut off involuntarily from the program, whether fewer physicians are prescribing or whether barriers to accessing safer supply have increased.
‘Dependence, tolerance, addiction’
Some experts say the decline in safer supply participation is due to physicians being influenced by their peers and public controversy over the program.
Dr. Karen Urbanoski, an associate professor in the Public Health and Social Policy department at the University of Victoria, says peer influence plays a significant role in prescribing practices.
A 2024 study found the uptake of prescribed safer supply in B.C. was closely tied to prescribers’ professional networks.
“These peer influences are apparent for both the uptake of [safer supply] prescribing and its discontinuation — they are likely playing a role here,” Urbanoski said in an email to Canadian Affairs.
Urbanoski also points to the broader environment — including negative media coverage and uncertainty about program funding — as factors behind the decline.
“Media discourse and general politicization of [safer supply] has likely had a ‘cooling effect’ on prescribing,” she said.
Dr. Leonara Regenstreif, a primary care physician and founding member of Addiction Medicine Canada, says many physicians embraced safer supply without fully grasping its clinical risks. Addiction Medicine Canada is an advocacy group representing 23 addiction specialists across Canada.
Regenstreif says physicians too young to have practiced during the peak of OxyContin prescribing were often enthusiastic prescribers of safer supply in the program’s early days. OxyContin is a prescription opioid that helped spark North America’s addiction crisis.
“In my experience, the MD colleagues who have embraced [safer supply] prescribing most zealously … never experienced the trap of writing scripts without knowing what was ahead — dependence, tolerance, addiction, consequences,” her emailed statement says.
Now, many of these physicians are looking for an “exit ramp,” Regenstreif says, as concerns over safer supply diversion and its treatment benefits grow.
Reib, of the UBC, says some of her colleagues in addictions medicine fear speaking out about their concerns with the program.
“Some of my colleagues have had their lives threatened by their patients who have become financially dependent on selling their [hydromorphone],” said Rieb.
The College of Physicians and Surgeons of B.C., which represents physicians in the province, referred Canadian Affairs’ questions about declining program participation to the health ministry and the BC Centre on Substance Use. The centre was unable to provide comment by press time.
Public backlash
The decline in B.C.’s safer supply participation unfolds amid mounting scrutiny of the program and its effectiveness.
Rieb says that the program’s framing — as free, safe and widely available — may run counter to longstanding public health strategies aimed at reducing drug use through pricing and harm awareness.
“Drivers of public use of substances are availability, cost, and perception of harm,” she said. “[Safe supply] is being promoted as safe, free and available for the asking.”
There have been reports of youth gaining access to diverted safer supply opioids and developing addictions to fentanyl as a result. Last September, B.C. father Gregory Sword testified before the House of Commons that his teenage daughter died after accessing diverted safer supply opioids.
B.C.’s recent decision to overhaul its prescribing guidelines followed revelations of a widespread scam by dozens of B.C. pharmacists to exploit the safer supply program to maximize profits.
Experts also note that Canada still lacks the evidence needed to assess the long-term health outcomes of people in safer supply programs. There is currently no research in Canada tracking these long-term health outcomes.
“There is a lack of research to date on retention on [safer supply],” said Urbanoksi.
Rieb agrees. “There are many methodological problems with the recent studies that conclude [the] benefit of pharmaceutical alternatives (‘safe supply’),” she said.
“We need long term studies that look at risks/harms as well as potential benefits.”
Regenstreif says the recent drop in participation may have an unintended upside — encouraging more people with substance use disorders to try what she sees as a more effective treatment: opioid agonist therapy, or OAT. This therapy uses medications like methadone or buprenorphine to reduce withdrawal symptoms and cravings.
“If fewer people are accessing [safer supply] tablets … more people with [opioid use disorder] might accept proper OAT treatment,” she said.
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.
By Alexandra Keeler
From cancer to heart disease to brain damage, the evidence of alcohol’s harms is mounting. So why are governments making it easier to drink?
In May, shortly after Parliament resumed, Quebec Senator Patrick Brazeau introduced Bill S-202, a private member’s bill to require nearly all alcoholic beverages to carry health warning labels.
“As a former alcohol consumer, I was once in the 75 per cent of Canadians who are not aware that there is a causal link between alcohol consumption and seven cancers,” Brazeau told the House of Commons on June 3.
“I personally battled colon cancer several years ago, so much so that when I received treatment, I felt I was being killed inside.”
Brazeau is something of an outlier in government. Public health experts say Canadian governments are not doing enough to address alcohol’s known health risks — and that the alcohol industry is a big part of the problem.
“We’ve known about the carcinogenic effects of alcohol since the 80s,” said Peter Butt, a University of Saskatchewan researcher and co-chair of Canada’s latest drinking guidelines. “But there are no warning labels, so the consumer is given false confidence.
“Some of this falls at the doorstep of the government, because they regulate the labeling.”
Alcohol harms
Today, the World Health Organization warns that alcohol harms nearly every system in the body.
The International Agency for Research on Cancer classifies alcohol as a cause of six cancers.
Chronic alcohol use raises the risks of liver and heart disease, brain damage, mental health issues, injuries and fetal alcohol spectrum disorders.
In Canada, the federal government oversees labeling and public health messaging rules, while the provinces control liquor sales and drinking ages.
In January 2023, Health Canada released updated national alcohol guidelines in response to the growing evidence of alcohol-related harms. This new guidance marked a major departure from its 2011 recommendations, which had suggested women not exceed 10 drinks per week and men not exceed 15.
The new guidelines have a sober message: no amount of alcohol is risk-free, and risk rises significantly with more than two drinks a week.
“We didn’t say you shouldn’t drink more than two standard drinks a week. We said you should reduce the amount that you drink,” said Butt, who co-chaired the team that updated the guidelines.
“The consumer had a right to know.”
Mixed messages
Aside from tightening its guidelines, Canadian governments have done little to better protect the public.
Public health experts say one major flashpoint has been warning labels. In general, drinks with greater than 0.5 per cent alcohol content are exempt from standard food and beverage labeling requirements.
“Even bottled water or non-alcoholic beer has to have the nutrition facts because it doesn’t have enough alcohol in it to get the exemption,” said Adam Sherk, a research scientist at the Canadian Centre for Substance Use and Addiction who also advised on Canada’s updated alcohol guidelines.
The Canadian Cancer Society has been advocating for labels on alcohol products since 2017. The Canadian Institute for Substance Use Research has done the same since 2023. But Health Canada has not initiated any regulatory process to mandate warning labels for alcohol products.
Some research indicates such labels could reduce sales.
A 2020 study by the Yukon government and the Canadian Institute for Substance Use Research tested how warning labels affect consumer behaviour. It found labels did increase awareness and reduce sales.
Yukon pulled its label requirements after the alcohol industry threatened to sue the government.
Convenient
Labelling is just one of many measures governments could take to reduce alcohol-related harm.
In addition to labels, the Canadian Alcohol Policy Evaluation project recommends minimum unit pricing, marketing and advertising controls, and public education campaigns. No province or territory has fully implemented all of these measures.
“[T]he Canadian federal government has not adopted or only partially adopted many evidence based alcohol policies,” the project’s report reads.
Meanwhile, some provinces are moving in the opposite direction.
Nova Scotia is considering expanding retail options. In April, Quebec rejected a recommendation to lower its blood alcohol limit for drivers, despite repeated coroner warnings.
Ontario has gone the furthest.
The province plans to invest $175 million over five years to grow its alcohol sector. It has begun permitting alcohol sales in convenience stores for the first time — with up to 8,500 new retailers expected to carry alcohol by 2026. It has also scrapped previous limits on pack sizes and discount pricing.
In April 2024, the province’s chief medical officer, Dr. Kieran Moore, recommended raising the legal drinking age from 19 to 21. Premier Doug Ford rejected the idea, arguing that if 18-year-olds can enlist in the military, they should be allowed to drink.
“We believe in treating people like adults,” he told media at the time.
In late June, the province also approved alcohol consumption on so-called “pedal pubs” — large, multi-person bicycles equipped with a U-shaped bar, often used for tours or bachelor parties.
“There’s never been such a large increase in availability all at once,” said Sherk, calling Ontario’s expansion “unprecedented.”
False profits
Tim Stockwell, a University of Victoria professor and former director of the Canadian Institute for Substance Use Research, says corporate influence helps explain why governments are failing to address alcohol’s health risks.
“Evidence for harms from alcohol has been with us for decades and has only strengthened,” said Stockwell. “Commercial vested interests have always dominated the policy sphere.”
Federal lobbying records show Beer Canada has routinely targeted Health Canada and more than two dozen federal agencies to influence policy on labeling, taxation and public health messaging. This includes closed-door meetings with MPs and senior officials from the Department of Finance and Agriculture Canada.
Beer Canada did not respond to multiple requests for comment by press time. Spirits Canada and Molson Coors Beverage Company also did not respond to multiple requests for comment.
Butt, of the University of Saskatchewan, says the money governments generate from alcohol sales creates a conflict with their public health mandate.
Federal and provincial governments generate revenue from alcohol through a range of mechanisms, including excise taxes, provincial markups, sales taxes and licensing fees. In some provinces, governments also earn profits from government-run liquor stores.
“[Governments] look at it from a lost revenue perspective, rather than from a public health perspective,” said Butt.
Ian Culbert, of Public Health Canada, puts it more bluntly. “Governments have a substance sales issue, as opposed to a substance use issue,” he said. “But it’s short-term gain for long-term pain.”
“Public Health wants to reduce consumption, because all consumption contributes to harm,” said Stockwell, of the Canadian Institute for Substance Use Research. “Commerce wants to … expand the consumption.”
A familiar playbook
Every expert interviewed for this story said the alcohol industry is following the tobacco industry’s playbook.
“They’re using the same sort of rear-guard action policies: denial, heavy government lobbying, government revenue,” said Butt.
“I don’t trust either the industry nor the government to do the right thing based upon past action. I think it’s important that consumers are educated.”
Adam Sherk agrees. “If I was [the industry], I would also be scared about consumers knowing this link [to cancer] better,” he said.
“The strategy is to obfuscate the link — point to studies that might be older or found no link, or put a lot of things in the water so it seems less clear than it is.”
But alcohol, experts say, is harder to regulate than tobacco. “Nobody liked to be in an airplane with smokers eating dinner next to smokers, so it was really easy to demonize smoking,” said Culbert.
“Alcohol is so ingrained in everything: we drink when we’re happy, we drink when we’re sad, we drink when we’re bored — we drink.”
Still, the normalization does not make the risks any less real. “There’s a mortality rate attached to this,” said Butt.
“And that’s the thing that is tragic — this is a modifiable risk factor.”
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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