Cannabinoid hyperemesis syndrome causes severe nausea, vomiting, and abdominal pain in some marijuana users—but no one really knows why.

By Maggie O'Neill
March 26, 2019

Experts are growing increasingly concerned about a possible side effect of cannabis that causes vomiting, abdominal pain, and nausea in some marijuana users called cannabinoid hyperemesis syndrome (CHS). According to a new study published in the journal Annals of Internal Medicine, 18.4% of people who inhaled cannabis and ended up in the emergency room of a Colorado hospital and 8.4% of those who ate edible cannabis and ended up in the emergency room had CHS symptoms.

As marijuana becomes legal in more states, doctors are starting to pay more attention to CHS, which was first identified in Australian research in 2004. Health spoke to Joseph Habboushe, MD, who specializes in emergency medicine at NYU Langone, to learn more about CHS—and why you’ll likely be hearing more about CHS in the future.

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Right now, what’s known about CHS is sparse, Dr. Habboushe says. “There’s not much research out there. At a high level, a lot more research needs to be done. In this time when we are accepting marijuana more, we have to see that any drug out there has a side effect."

The patients who reported CHS symptoms in the 2004 study on the condition "were all folks who’d been smoking for years,” he says. While it’s possible to use marijuana for years without experiencing symptoms of CHS, once a person does experience CHS symptoms, the symptoms tend to stick around as long as the person continues using marijuana. If you quit using marijuana because of CHS and then, at some point later on, take it up again, CHS symptoms will likely return.

In January 2018, Dr. Habboushe published a paper on CHS that found that among patients who use marijuana “regularly”—defined as at least 20 days a month—“roughly a third seemed to have some symptoms to fit CHS.” Those people, he says, end up most frequently in either an emergency room or a gastroenterologist’s office—where they’re often misdiagnosed. Doctors might try to rule out pregnancy, anemia, and esophageal and digestion complications before diagnosing someone with CHS.

Dr. Habboushe says nobody has a solid answer to the question of why marijuana induces CHS. Researchers don’t think the onset of CHS is related to the way users consume marijuana; smoking marijuana or eating cannabis edibles can both lead to CHS symptoms.

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Stopping marijuana use is the only known way to permanently alleviate CHS symptoms, but it takes time. “We know that if you stop smoking you get better, but it takes days to weeks,” Dr. Habboushe says. Among CHS patients studied in 2004, taking hot showers had also helped alleviate symptoms; some people with CHS end up taking hot showers for hours a day just to get some relief from severe symptoms, he adds.

Dr. Habboushe stresses the fact that many of the CHS cases making headlines reflect the symptoms of patients who use marijuana very frequently. Not everyone who uses marijuana will get CHS, and not everyone who gets CHS will have symptoms that warrant a trip to the emergency room. But more research is needed to understand who is truly at risk. “If we’re going to start accepting marijuana more,” he says, “we need to be willing to study it.”

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