Cannabis Made Clear

What Is Cannabinoid Hyperemesis Syndrome (CHS)?

nauseous person with stomach ache

For some people, cannabis may alleviate pain and nausea. For others, it can have the opposite effect. In fact, abdominal pain, nausea and cyclical vomiting may all be tell-tale signs of cannabinoid hyperemesis syndrome (CHS), a condition known to hit some daily cannabis consumers seemingly out of the blue. Because the symptoms of CHS can be misinterpreted, education is key. This article offers an overview of what CHS is, what its symptoms are and how to treat them.

What is cannabinoid hyperemesis syndrome (CHS)?

Cannabinoid hyperemesis syndrome is a condition that some people who consume high-intensity cannabis daily may experience. Its symptoms — nausea, cyclical vomiting and abdominal pain — can occur sporadically, and its triggers are not well known.

According to the Canadian Medical Association Journal: “Patients [with CHS] are often misdiagnosed with cyclical vomiting syndrome — both conditions involve abdominal cramping, nausea, and repeated severe bouts of vomiting. The main difference is CHS affects patients with a history of daily, long-term cannabis use.” 

It may take years for CHS symptoms to develop. It may also take a long time to pinpoint CHS as the cause; one U.S. study showed that CHS patients went to the ER 17.9 times before being diagnosed with the condition. The only way to definitively diagnose CHS is if symptoms resolve after abstaining from cannabis.

The first known cases of CHS were reported in South Australia in 1996. Researchers are still working to get to the bottom of this condition, and the suddenness of CHS onset — often after years of daily cannabis consumption — has been especially perplexing.

What are the symptoms of CHS?

People with CHS can experience cyclical vomiting episodes, nausea and stomach pains. This can lead to weight loss and dehydration.

The Canadian Medical Association Journal describes one patient who was overcome with a sudden bout of nausea one morning. After vomiting, the nausea continued, and they spent the rest of the day “dry-heaving on the bathroom floor.” They also “couldn’t drink water” or keep food down.

What causes CHS?

While the exact cause has yet to be discovered, the only link that has been identified is heavy cannabis consumption — daily for a year or more, or consuming products high in THC.

Scientists like Dr. Ethan Russo, a neurologist and medical researcher who has spent the past 27 years investigating cannabis, suspect CHS may be linked to an inability of certain people to metabolize THC. Research suggests that once CHS develops, even small amounts of THC — including microscopic doses in CBD-dominant products — can trigger a flare-up. Any kind of cannabis product can be a trigger, including joints, edibles and capsules. Worse, these flare-ups can last weeks.

Who does CHS affect?

A Canadian Medical Association Journal article estimates that one in every 200 frequent cannabis consumers between ages 16 and 44 will get CHS.

Russo has seen many patients who exhibit signs of CHS. He’s noticed they tend to consume cannabis heavily, often products high in THC. In one of his studies, participants consumed an average of four grams of flower material a day — between two to four buds.

After years of heavy consumption, CHS sufferers suddenly begin feeling sick. Russo is careful to note that CHS is markedly different from “greening out” or having a negative reaction to too much THC. “It’s only CHS when there is this recurrent nausea, vomiting, abdominal pain and this unusual behaviour of spending hours in the hot shower or bath to reduce symptoms,” he says.

Why does CHS occur in only some cannabis consumers?

In a 2022 paper for the peer-reviewed journal Cannabis and Cannabinoid Research, Russo and his co-authors argue that mutations in five genes and receptors linked to human metabolism seem to be connected to the condition.

“The vast majority of CHS patients had at least two of these gene mutations, and there were a couple of people who had all five,” says Russo. He says a cheek-swab test, like the kinds used in at-home DNA testing, could eventually help detect these mutations.

What is the treatment for CHS? 

Health Canada says many sufferers of CHS find temporary relief after a hot shower or bath. Additionally, the Canadian Medical Association Journal says topical capsaicin cream — an active component in chili peppers — and certain prescription medications can alleviate symptoms.

The success of pills, creams and baths is limited, however. The only thing that appears to resolve CHS episodes is avoiding cannabis altogether. Russo says clinical evidence and research on CHS demonstrates multiple cases in which symptoms disappeared when cannabis was cut out entirely, only to recur almost immediately after consuming THC — even after years of abstinence.

More patient and clinical awareness of CHS is needed

For most patients, the first step to a CHS diagnosis begins in a doctor’s office or hospital emergency room. Patients arrive needing immediate relief from symptoms, including dehydration, intense abdominal pain, nausea and vomiting — ambiguous symptoms that could be signs of countless illnesses.

Typically, says Russo, one of two things happens: CHS is either mistaken for another condition, such as cyclical vomiting syndrome, or it’s too quickly diagnosed in people who really do have other health issues. “That's why it’s necessary to be very thorough in talking to people and analyzing the situation and, if necessary, doing a genomic screening test,” he says.

What should I do if I suspect I have CHS?

If you are a regular cannabis consumer and suddenly begin experiencing abdominal pain, cyclical vomiting and nausea, the easiest way to know if you have CHS is to stop consuming cannabis for a while.

Even small amounts of THC should be avoided, as the threshold for what may trigger a flare-up is not yet known. It’s also not known if CHS can affect people who consume only cannabis without THC (such as CBD products). With that in mind, the best bet is to avoid cannabis altogether.

As for how long to stay abstinent, Russo says CHS symptoms can linger for a couple of weeks after stopping. For some people, it may take more than a month to start noticing improvements. For others with CHS, episodes occur every few months, which means it may take longer for symptoms to alleviate.

If your symptoms eventually disappear — only to return when you consume THC — it could very well be CHS. At this point, you should consider bringing this information to a health-care provider for a formal diagnosis.

It’s still unknown just how prevalent CHS is. Ensuring better health outcomes for cannabis consumers demands greater awareness of the condition — both among consumers and medical workers.


Cannabinoid Hyperemesis Syndrome
National Library of Medicine
Clues emerging to mysterious cannabinoid hyperemesis syndrome 
Canadian Medical Association Journal
Frequent vomiting from use of cannabis
Canadian Centre on Substance Use and Addiction
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