Some pot users are suddenly hit by intense nausea and vomiting. What’s behind it?

Some pot users are suddenly hit by intense nausea and vomiting. What’s behind it?


Cannabinoid hyperemesis syndrome impacts longtime cannabis users seemingly out of nowhere, disrupting their stomachs and their lives.

As cannabis use increases in America, more experts are calling for better messaging about the risks associated with it. Elaine Thompson / AP, File

As cannabis use becomes more popular nationwide, especially among young people, there is a growing movement to educate the public about the various risks associated with it. Cannabis use can hamper brain development, contribute to anxiety and depression, cause fetal growth restriction in pregnant women, and make driving substantially more dangerous. 

But one lesser-known risk is not getting the attention that some experts say it should. It seemingly comes out of nowhere, affecting long-term users who likely enjoy the drug and find it beneficial in a myriad of ways. All of a sudden, their lives can be significantly disrupted by persistent nausea and violent vomiting. To make matters worse, many of them will be left in the dark about the true nature of their condition and the fact that it is even linked to the pot that they’ve been enjoying for months or years. 

This is known as cannabinoid hyperemesis syndrome, or CHS. While most cannabis users will dodge this bullet, those who rely on the drug for long stretches of their lives are at risk of having it suddenly turn on them without warning. This is what you need to know. 

The basics

“It’s not unusual that a drug will affect people in different ways, but this is a particularly striking way that a drug would affect somebody,” Jodi Gilman, director of neuroscience at the Massachusetts General Hospital Center for Addiction Medicine, told 

There are a lot of unknowns regarding CHS, even to experts like Gilman. But there are some things that we do know. 

CHS causes cyclical nausea, vomiting, and abdominal pain in people that have been using cannabis for a long period of time without these symptoms. It is most often seen in people who have been using cannabis daily for more than a year. 

Gilman separates the symptoms into two distinct phases. At first, CHS can manifest in morning nausea and sporadic abdominal pain. Then, CHS can cause ongoing nausea, repeated episodes of vomiting, and more sustained abdominal pain. All these things can in turn cause weight loss, decreased food intake, and dehydration. Vomiting can be intense and even “overwhelming” at this point, usually forcing people to seek medical care of some sort. 

CHS symptoms seem to wax and wane, wreaking havoc for a few days before subsiding to a more manageable level and then flaring up again. 

“It’s extremely debilitating. People are miserable,” Gilman said. 

Doctors like Sushrut Jangi, a gastroenterologist at Tufts Medical Center, have seen the effects of CHS firsthand. 

“As people are using cannabis more and more, we’re clinically seeing the downstream effects of this. I have many, many patients in our clinics that have these kinds of symptoms and they’re using cannabis regularly,” he told 

How does this happen? The answer lies in the somewhat mysterious endocannabinoid system, which controls a host of critical body functions. The human body has lots of receptors in the brain and the gut that bind to THC, the psychoactive substance in cannabis that gets users high. These receptors start to change over time after sustained cannabis use, Jangi said. 

The endocannabinoid system plays a vital role in regulating appetite and nausea. Even limited exposure to THC can affect the stomach, esophagus, or sphincter, Gilman said. 

“As these receptors change, your body starts to process signals that regulate appetite and nausea differently,” Jangi said. 

Researchers are very early on in understanding the specifics of the mechanisms at play in CHS, he added, and receptors in the brain can be particularly hard to study. Some state-specific or emergency room-specific studies have occurred, but Jangi said there is a serious need for a large-scale epidemiologic study.

Experts have tried to determine the prevalence of CHS, but this has proven to be very difficult, Jangi said. Somewhere between 5% and 20% of chronic cannabis users will experience CHS in some capacity, he estimated. 

Diagnosing CHS can also be tricky. Both Gilman and Jangi doubt most cannabis users know about CHS. Even some primary care physicians remain in the dark.  

“Sometimes people will go to their doctor and the doctor won’t identify this as CHS because they haven’t heard of it,” Gilman said


There is no concrete diagnostic test for CHS. The only way to diagnose it without a doubt is to have the patient stop using cannabis and to see if that helps relieve their symptoms, both Gilman and Jangi said. 

Therefore, the only surefire way to get rid of CHS is to simply stop using cannabis. 

“The problem is, a lot of patients are not willing to stop cannabis, or it’s very difficult to stop. Or they don’t believe that that is the cause,” Jangi said. 

Cannabis is unequivocally an addictive substance, Gilman said. It contains a psychoactive compound that causes feelings of euphoria, and neuroimaging shows that it triggers the same circuitry in the brain as any other drug that can be abused. Experts used to estimate that about 10% of cannabis users would become addicted, she said. More recent data shows that around 30% of daily users will have trouble stopping. 

Myths about cannabis not being addictive are likely rooted in outdated forms of cannabis consumption, Gilman said. Until recently, most cannabis was consumed by smoking “flower” in a joint or pipe. For decades, the cannabis that most people smoked had THC levels around 3%, she added. The current products sold in dispensaries blow these numbers out of the water. 

“Now, the products are so much more potent, they’re so many more of them. There’s all these edibles that are now available, there are waxes, there are dabs, shatters, and kids can use them all day in school without anyone knowing because they’re smokeless and odorless. We don’t know how addictive these high-potency products are, quite frankly,” Gilman said. 

So, if someone has CHS and is unwilling to stop using cannabis, what can be done? A couple imperfect options exist to treat it. Doctors can prescribe anti-nausea medications, Jangi said, but treating one drug with another is not particularly efficient. Most anti-nausea medications are also not that effective in getting rid of symptoms, he added. 

Those suffering from severe nausea sometimes turn to hot showers or baths to relieve their symptoms. This can work, Jangi said, because human skin is thought to have heat receptors that interact with the endocannabinoid system. Ointment containing capsaicin (the stuff that gives spicy food its “heat”) can similarly be used to treat nausea and vomiting. 

Spreading the word

As cannabis legalization spreads, more people are experiencing CHS and therefore knowledge about the condition is spreading, Gilman and Jangi said. 

But a lot more can be done to educate the public and doctors on the adverse effects of cannabis. For one, the warning labels on these products could be a lot more specific, Gilman said. She stressed that there are a lot of reasons to decriminalize cannabis, but society needs to be open about the risks so that people can make their own informed decisions. 

“I think legalization proponents didn’t want to derail this by focusing on negative health outcomes,” she said. “There is this tendency to underplay any negative effects from cannabis because it’s become a political issue.”

Creating strict guardrails around how potent cannabis products are allowed to be would go a long way toward decreasing addiction and negative health outcomes, Gilman said. 

Jangi highlighted the need to decrease stigma around getting treated for CHS or other issues caused by cannabis use. He advocated for using cannabis revenue to fund more research. 

“If we’re collecting so much revenue from this, a portion should be allocated to doing research in this area. If you’re exposing this many people to cannabis, we need to make sure we’re not putting people at risk,” he said. 

Above all, both Jangi and Gilman reiterated the importance of seeking health care, believing in scientific research, and being transparent with doctors. 

“Some people don’t believe this is real,” Gilman said. “But this is happening.”

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