"The prevalence of cannabinoid hyperemesis syndrome increased by a third with the legalization of cannabis in Canada in 2018," explains Christopher Andrews, a gastroenterologist at the University of Calgary who reported on the issue a year ago in the journal Alimentary Pharmacology & Therapeutics. "At the beginning of the pandemic, there was a sharp increase, with a prevalence twice as high as before legalization."
This syndrome is characterized by uncontrollable vomiting that takes patients to the emergency room. "We've been seeing more and more of this over the last ten years or so," confirms Martin Laliberté, emergency physician and toxicologist at the McGill University Health Centre (MUHC). "These patients are difficult to follow. After they leave the ER, we often don't hear from them again."
How can a substance associated with cravings cause such nausea? "It's a disruption of the endocannabinoid system due to heavy consumption of cannabis with a high concentration of THC," explains the world's leading authority on this syndrome, gastroenterologist Thangam Venkatesan, from Ohio State University.
Dr. Venkatesan, who follows 1,600 patients with or who have had this syndrome in the United States, Canada and India, has discovered that this high consumption makes the endocannabinoid system more vulnerable to stress.
It's a system that helps us respond to stressors," she says. Cannabis activates it, which reduces the stress response. But if you consume too much cannabis with a high THC content, the receptors of the endocannabinoid system become less numerous because they're over-stimulated by cannabis. Paradoxically, this makes you more vulnerable to stress. Sometimes, just getting up in the morning becomes too stressful, and you start vomiting uncontrollably."
According to Dr. Andrews, about six out of every thousand cannabis users in Canada have this problem. But since only 18% of cannabis users consume it every day, according to Statistics Canada data, the risk is higher among frequent users. And if you consume THC concentrates, with levels exceeding 75% rather than 20% in normal cannabis, the risk is even higher," says Dr. Venkatesan. This problem has arisen because even in normal cannabis, THC levels are much higher than they used to be. Thirty years ago, cannabis only contained 4 or 5% THC."
Heat can reduce the symptoms of cannabinoid hyperemesis syndrome. "People can take up to 10 or 15 hot showers a day," says Dr. Venkatesan.
While some antipsychotics could potentially also reduce symptoms, the only solution is to stop cannabis to allow the receptors of the endocannabinoid system to recover from overstimulation, according to Dr. Andrews.
"After six months of abstinence, normally the number of receptors in the system returns to normal," says Dr. Andrews. There are studies of molecules that might stimulate receptors to help control vomiting, without impeding receptor reactivation during abstinence."
There are beginning to be resources to help regular cannabis smokers quit, as with alcohol and other drugs, reports CHUM psychiatrist Didier Jutras-Aswad.
Heredity
There is also a less common non-cannabinoid hyperemesis syndrome, according to Dr. Venkatesan. "A lot of the cases are pediatric and related to heredity," she says. It seems to be related to a family history of migraine."
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37 %
Proportion of Canadians aged 16 to 19 who have used cannabis in 2022
Source: Statistics Canada
50 %
Proportion of Canadians aged 20-24 who used cannabis in 2022
Source: Statistics Canada
25 %
Proportion of Canadians over 24 who used cannabis in 2022
Source : Statistics Canada
Source : De mystérieux vomissements liés au cannabis : https://www.lapresse.ca/actualites/sciences/2024-02-05/de-mysterieux-vomissements-lies-au-cannabis.php#