Kennon Heard, MD, PhD, was skeptical when he first heard about cases in emergency departments of severe, recurring episodes of nausea and vomiting associated with chronic use of marijuana.
In 2004, Australian researchers were among the first to describe the phenomenon, labeling it cannabinoid hyperemesis syndrome, or CHS. A few years later, a colleague told Heard, “I think I saw this guy with this cannabinoid hyperemesis thing.”
“And I’m like, ‘That’s not real. That’s made up. There’s no such thing as this. That’s the dumbest thing I’ve ever heard of,’” Heard recalls thinking. “Three years later, we were up to our eyeballs in it.”
Colorado, a pioneer in legalizing cannabis, has been at the forefront of the rise of CHS, which has acquired a social media nickname: “scromiting,” for a combination of screaming and vomiting.
Heard is a professor in the University of Colorado Anschutz Department of Emergency Medicine and its section chief of medical toxicology. He estimates that the emergency department at UCHealth University of Colorado Hospital, where he practices, sees people with CHS “multiple times a week. It’s not surprising to see at least one person in our ED with it at any point in time.”
Heard describes CHS as “episodes of recurrent nausea, vomiting, and abdominal pain, occurring in the setting of heavy, ongoing cannabis use – usually daily and for at least a year. It’s not consistent – there are people who will use that much cannabis forever and never have a problem, and there are others who will have it. And among those who have it, for whatever reason, they might be in the ED four, five, six times, and then get better.”
Episodes of CHS are often worst in the morning, with “severe, unremitting nausea; recurrent vomiting; and dry heaves that go on for hours,” he says. And at times it can cause “significant medical outcomes. We’ve seen patients who have vomited themselves into kidney failure or have torn their esophagus and ended up needing surgery.”
In 2000, Colorado became one of a handful of states that legalized the use of marijuana for medicinal purposes if authorized by a provider. That, coupled with a 2009 decision by the U.S. Department of Justice to ease up on marijuana enforcement, pushed up cannabis sales in Colorado and elsewhere.
“The dispensaries started opening on every corner,” Heard says. “All of a sudden, we started seeing all these people with cyclic vomiting presenting in the emergency department, a two- to three-fold increase.”
In 2015, a study by Heard and several CU Emergency Medicine colleagues reported that CHS presentations at the EDs of UCH and Denver Health nearly doubled after the liberalization of medical marijuana.
In 2014, after the period covered in Heard’s 2015 study, Colorado became the first state to allow marijuana sales for recreational use. Between 2014 and 2021, annual cannabis sales in the state rose 226%. Other states soon followed suit with legalization, and now almost half the states permit recreational cannabis sales.
Because Colorado “was out in front of decriminalizing cannabis, we saw CHS pretty early,” Heard says. “As state after state makes cannabis more available, we’re seeing the same cycle over and over.”
A nationwide study by University of Illinois Chicago researchers, published in November 2025, sifted data from more than 188 million U.S. ED visits from 2016 to 2022. It found that CHS cases presented in the ED rose from 4.4 per 100,000 ED visits to a peak of 33.1 per 100,000 in the COVID-19 year of 2020, and remained elevated in 2022 at 22.3 per 100,000 visits.
The study’s authors said they may have undercounted CHS cases because of a lack of a consistent diagnosis code for the syndrome in medical records, and because some patients may not have admitted their marijuana use to their providers. (A diagnostic code for CHS was finally published in October 2025.)
A study published in December 2025 examined data from more than 15 million ED visits in Massachusetts, which legalized recreational marijuana in 2016. The study showed that the rate of CHS cases in that state exploded from 0.729 per 10,000 ED visits in 2012 to 10.6 per 10,000 in 2021. People aged 18-34 years experienced the fastest rise in CHS prevalence, the study said.
Many questions remain to be answered about CHS, including exactly how cannabis triggers the condition. But experience tells Heard that there’s “almost certainly” a link between higher CHS incidence rates and the increased potency of cannabis today. “When I was growing up, I knew plenty of kids who smoked pot every day, and I never saw this,” he says.
The “vast majority” of CHS cases Heard and his colleagues encounter involve people who smoke marijuana, which remains the most common means of cannabis use, although he has seen occasional reports of CHS patients who have used edible cannabis products.
When Heard first started seeing CHS in the ED, “it was very frustrating, because these people are miserable, and the standard antiemetic nausea medicine we would give at the time was not effective for them. We would give them IV fluids, because they were usually pretty dehydrated. We would check their kidney function and electrolytes. Maybe they would get better and maybe not. It was very common that you would treat someone, and four hours later they would be right back.”
Eventually, Heard says, “we started to recognize that some older antiemetics, and even some psychiatric medications off label, were much more effective at treating CHS. There’s been at least one well-designed trial showing that. So now that’s pretty much become the standard treatment, along with fluids. Most of the time we can get their symptoms controlled.”
There’s been social media chatter about hot baths and showers as a home remedy for CHS. “There are people who will tell you that can work, but I don’t know of any studies around that,” Heard says.
Ultimately, the “cure” for CHS is to stop using cannabis, Heard says. But some CHS sufferers he’s treated who have made multiple trips to the ED continue to use the drug.
“I’m not an addiction specialist,” he says, “but that is one of the clearest examples I’ve seen of addiction in action.”