Doctors in the United States are seeing more and more cases of a puzzling illness tied to heavy cannabis use.
Known as cannabinoid hyperemesis syndrome (CHS), this condition causes repeated bouts of severe vomiting, and it appears to be growing fast in emergency departments across the country.
According to a new study from the University of Illinois Chicago, CHS cases rose sharply between 2016 and 2022 and have remained high since then.
As of 2025, nearly half of all Americans live in states where recreational cannabis is legal. With more people using cannabis through legal or medical programs, health experts are beginning to notice harmful side effects that were once rare or misunderstood. CHS is now recognized as one of the more serious issues among frequent cannabis users.
CHS was first described by doctors in Australia in 2004. At first, its cause was a mystery. People with CHS would often come to the hospital with intense vomiting, nausea, and stomach pain.
In some extreme cases, they even scream in pain while vomiting—a symptom now nicknamed “scromiting.” Many of these patients found some relief by taking long, hot showers or baths. This odd habit is now considered a possible sign of CHS.
The syndrome appears in three stages. First is the prodromal phase, with nausea and stomach discomfort, sometimes lasting months. Then comes the hyperemetic phase, with repeated vomiting over several days. Finally, there’s the recovery phase—when people stop using cannabis, their symptoms gradually go away, sometimes in just a few days or weeks.
Before CHS had an official name, doctors often misdiagnosed it as other vomiting conditions, leading to unnecessary testing and treatments. Only recently, in 2025, was a specific medical code (ICD-10 code F12.188) created to help identify CHS.
In the study, published in JAMA Network Open, researchers looked at nationwide emergency room data from 2016 to 2022. They used data from a national hospital database that includes a sample representing nearly 85% of the U.S. population.
They found that CHS mostly affected younger adults, especially those between 18 and 35 years old. On average, CHS patients were about 30 years old. Unlike many other cannabis-related conditions that are more common in men, CHS affected men and women almost equally.
Most CHS cases were found in the western and northeastern U.S., where cannabis legalization happened earlier. Black patients accounted for nearly 25% of CHS visits. In most cases, CHS occurred without the presence of other drug or alcohol use.
The number of CHS cases per 100,000 emergency visits increased dramatically—from about 4 in 2016 to over 22 in 2022, peaking at 33 in early 2020. At the same time, visits for cyclic vomiting syndrome (a similar condition) dropped, suggesting doctors are getting better at recognizing CHS.
The study also found that people aged 18 to 25 were more than three times as likely to be diagnosed with CHS compared to those aged 36 to 50. Although women are more likely to be diagnosed with vomiting disorders overall, men had slightly higher rates of CHS.
Researchers point out a puzzle: despite cannabis becoming more available in the years before 2020, CHS cases did not rise much until after the pandemic began. They suggest this may be because doctors didn’t know about CHS before, and patients were being misdiagnosed.
Now that CHS has a proper medical label, the authors say that hospitals need to be ready. In places where cannabis has just become legal, CHS may still be underdiagnosed. Without the right diagnosis, patients can go through painful symptoms, unnecessary tests, and unhelpful treatments.
To improve care, doctors should be trained to recognize CHS, especially in young adults with heavy cannabis use. Common warning signs include repeated vomiting, stomach pain, and the need for hot showers to feel better. New tools and screening methods could help doctors make faster and more accurate diagnoses.
The study’s authors also recommend using the new medical code consistently so researchers and health systems can track CHS more accurately in the future.
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The study is published in JAMA Network Open.
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