Mysterious vomiting linked to cannabis

Marijuana is associated with appetite. But for some frequent users, the drug is linked to serial vomiting. “Cannabinoid hyperemesis syndrome” is increasingly present in emergency rooms.

“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 took stock of the issue a year ago in review Alimentary Pharmacology & Therapeutics. “At the start of the pandemic, there was a sharp increase, with prevalence twice as high as before legalization. »

This syndrome is characterized by uncontrollable vomiting that lands patients in the emergency room. “We have seen this more and more over the last ten years,” confirms Martin Laliberté, emergency physician and toxicologist at the McGill University Health Center (MUHC). “These are difficult patients to follow. After they leave the emergency room, we often no longer hear from them. »

How can a substance associated with food cravings cause such nausea? “It is a disruption of the endocannabinoid system due to heavy consumption of cannabis with a high concentration of THC,” explains the world authority on this syndrome, gastroenterologist Thangam Venkatesan, of Ohio State University.

The DD 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 with the response to stressors,” she says. Cannabis activates it, which reduces the stress response. But if you consume too much cannabis with high THC levels, the receptors of the endocannabinoid system become fewer, because they are overstimulated by cannabis. So we paradoxically become more vulnerable to stress. Sometimes just getting up in the morning becomes too stressful and you start vomiting uncontrollably. »

According to the Dr Andrews, about six in a thousand cannabis users in Canada have this problem. But since only 18% of cannabis users use it every day, according to Statistics Canada data, the risk is higher among frequent users. “And if we consume THC concentrates, with levels exceeding 75% rather than 20% in normal cannabis, the risk is even higher,” says the DD Venkatesan. We saw this problem arise because even in normal cannabis, THC levels are much higher than before. 30 years ago, cannabis only contained 4 or 5% THC. »

Hot showers

Heat can reduce the symptoms of cannabinoid hyperemesis syndrome. “People can take up to 10 or 15 hot showers a day,” says the DD Venkatesan.

Although some antipsychotics could potentially also reduce symptoms, the only solution is to stop using cannabis to allow the receptors of the endocannabinoid system to recover from overstimulation, according to Dr.r Andrews.

“After six months of abstinence, normally the number of receptors in the system returns to normal,” says Dr.r Andrews. There are studies of molecules that could stimulate receptors to help control vomiting, without hindering receptor reactivation during abstinence. »

There are starting to be resources to help regular cannabis smokers quit, as with alcohol and other drugs, reports Didier Jutras-Aswad, psychiatrist at CHUM.


There is also a less common non-cannabinoid hyperemesis syndrome, according to the DD Venkatesan. “A good portion of cases are pediatric and linked to heredity,” she says. It seems to be linked to a family history of migraine. »

Learn more

  • 37%
    Proportion of Canadians aged 16 to 19 who used cannabis in 2022

    Source: Statistics Canada

    Proportion of Canadians aged 20 to 24 who used cannabis in 2022

    Source: Statistics Canada

  • 25%
    Proportion of Canadians over the age of 24 who used cannabis in 2022

    Source: Statistics Canada


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