The bizarre condition that makes some heavy weed users vomit non-stop

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Rachel awoke at around midnight on July 2, to the worst stomach pain and cramping she had ever felt in her life. She took a hit from her cannabis vape, which normally soothed her stomachaches. For the first time, though, it didn’t work. In fact, she started vomiting — and didn’t stop. After more than four hours of throwing up, she called her boyfriend, who rushed her to the emergency room.

She spent the next five hours in the ER, vomiting what she estimates to be a total of 20 times. Not until the nurses rubbed capsaicin cream — a medicine generally used to soothe joint pain — on her stomach did she stop writhing. They then hooked her up to an IV that dripped anti-nausea medication and, later, a sedative, before finally sending her home with her boyfriend. She stopped vomiting, but for the next five days, she still felt nauseous and ate little, mostly rice and applesauce. She lost 17 pounds over the course of those five days. “It’s probably the sickest I’ve ever been,” says the 32-year-old, who lives in Washington state.

Gary, a 42-year-old in Ontario, Canada, had a similar ER experience after ingesting weed. He suffered from relentless nausea for about 11 hours. Doubled over the toilet and drenched in sweat, he felt an intense urge to vomit, but couldn’t — so he shoved his fingers down his throat until he expelled an ounce or so of yellow bile. He had experienced a similar attack a few weeks earlier.

Before these episodes, Rachel and Gary had consumed weed on a pretty much daily basis for several years. (Both have chosen to remain anonymous out of concern for the possible professional and/or legal repercussions of their cannabis use, regardless of its legality.) They had come down with a bizarre and god-awful condition called cannabinoid hyperemesis syndrome (CHS), which is rare, but has gained buzz in recent years as more jurisdictions legalize recreational weed.

What is CHS?

CHS is basically severe, recurrent nausea and vomiting caused by weed — typically with heavy, long-term use; it can appear fairly randomly for these people. Due to the dearth of large academic studies, the prevalence of CHS isn’t entirely clear. But a 2018 study estimated that 2.75 million Americans may experience CHS each year, based on a survey of emergency department patients at a public hospital in New York City.

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CHS tends to have three phases. Symptoms of the prodromal phase, which can go on for long as months or even years, often include stomachaches, early morning nausea, and sometimes, fear of vomiting, according to Cedars-Sinai Medical Center. During this phase, some people turn to cannabis as a way to ease their nausea. It’s horrifically ironic: While these people might be smoking weed in order to calm their stomachs, the habit, in turn, makes them feel sicker.

People in the hyperemetic phase of CHS deal with constant, severe vomiting — way worse than what you might experience from the flu or even food poisoning. “You hear this deep, guttural vomiting that you don’t hear with other conditions,” says Eddy Lang, a physician and professor of emergency medicine at the University of Calgary. At least with other conditions, it settles down for a few minutes between vomiting attacks — but with CHS, it’s nonstop, he adds. It can start six to 12 hours after the person last used cannabis, and eventually, it can lead to dehydration and weight loss. Hot showers and baths, as well as capsaicin, seem to help. (More on that later.) Lang has seen hyperemetic patients stay in the ER anywhere from 6 to 12 hours

Finally, during the recovery phase, people stop feeling nauseous and vomiting, and can eat normally again — but consuming cannabis in any form will usually re-trigger symptoms, per Cedars-Sinai.

Lang thinks that there’s also a psychological component to CHS. Oftentimes patients (understandably) feel a lot of anxiety that accompanies the puking. They may also struggle to accept the connection between their weed use and their vomiting, which may be due to dependency on the substance, denial, or disbelief that the same weed that’s supposed to ease their nausea now causes it. Shortly after she arrived home from the hospital, Rachel experienced that very denial. “I don’t think this is CHS,” she told herself. “Let me take a hit.” Sure enough, she began vomiting again.

So why does weed cause nausea for some people?

Cannabis is linked to and does affect the digestive system, for better or worse. Indeed, several small studies have found that smoking weed can alleviate the vomiting and nausea that can result from chemotherapy, according to the American Cancer Society. CHS is “a paradoxical phenomenon that we don’t understand all that well,” Lang tells Mic.

In simplest terms, long-term, heavy cannabis use seems to alter the regulation of cell receptors that, when activated, make you feel nauseous. Normally, cannabis acts on those receptors to prevent nausea. But “in regular users, you get changes in the properties of the receptors in that they’re ultra-sensitive,” Lang says. Someone who consumes weed rarely, or not at all, won’t feel like puking while walking down the stairs, but someone with CHS probably would.

I smoke a lot of weed. Am I at risk for CHS?

There doesn’t seem to be a clear correlation between the amount of weed consumed and CHS risk, Lang says. “It’s not like you’re guaranteed to get CHS if you’re a daily user,” and in fact, it's rare, but even less frequent users may sometimes experience CHS.

How is CHS treated?

While symptoms can be managed, “there’s no cure [and] no way to make it stop suddenly,” Lang says. Hot showers and baths often alleviate nausea, so much so that seeking them for relief is a telltale sign of CHS, Lang says. The prickly heat from capsaicin cream (like what nurses applied to Rachel’s abdomen) can also provide relief. “It may have something to do with distraction,” Lang says. In other words, the burning sensation may take CHS patients’ minds off their nausea. Another possibility is that the heat acts on the hypothalamus, a brain region involved in not only regulating body temperature, but also vomiting, according to Cedars-Sinai.

Health providers typically use a combination of anti-nausea and anti-pain medications, as well as sedatives, for patients with CHS Lang says. (Some patients may even wake up from their sedative-induced slumber symptom-free, especially if anxiety is a main driver of their CHS.) And of course, they’ll also keep patients hydrated, given all the fluids they’ve puked up.

Ultimately, cutting off your weed consumption altogether is “probably the only way to keep the crisis at bay,” Lang says. While some people experience some residual symptoms after they stop using weed, they do eventually subside.

Rachel hasn’t completely given up cannabis, but she does limit herself to smoking what contains “super-low” percentages of THC (the compound that gets you high), and only on the weekends. Three weeks since her ER visit, she hasn’t experienced any CHS symptoms. Gary, on the other hand, hasn’t used weed at all since his ER trip — and doesn’t feel terribly compelled to do so again. “I’m scared straight,” he says. “You don’t even wish this on your worst enemy.”

While Rachel and Gary don’t villainize weed, they think more research is needed to identify and understand its potential side effects. Rachel points out that the substance’s illegality at the federal level in the US poses a barrier, though. Before going to the ER, she had no clue it was even a thing. Gary wants to contact Health Canada, the Canadian government’s national public health department, to share his CHS experience and encourage more research on it. “This thing is definitely real, and it sucks,” he says. “We’ve got to be more knowledgeable about it.” After all, amid the rise in legalization, ER docs can probably expect to see more cases of horror movie-grade puking in the years to come.