A rising link between vomiting syndromes and cannabis use is drawing more attention in the United States.
Cannabinoid hyperemesis syndrome (CHS) is a rare condition tied to chronic cannabis consumption. It features intense, cyclical nausea, abdominal pain, and vomiting. The first U.S. case was documented in 2009, and for a long time CHS lacked a national diagnostic code, making tracking difficult.
Emergency department visits are a key way researchers and clinicians identify who is affected and why. A study from the University of Illinois Chicago showed that CHS-related ER visits climbed from about 4 per 100,000 patients in 2016 to roughly 22 per 100,000 in 2022.
Although CHS remains uncommon, the trend warrants attention, especially since symptoms can be halted with proper care.
Importantly, using cannabis—even frequently—does not automatically doom someone to CHS. The condition affects only a small subset of cannabis users, with higher association to frequent use and younger age groups.
CHS typically develops gradually over the first years after starting cannabis, beginning with morning nausea or abdominal discomfort and potentially lasting for years. In a later, more severe stage, individuals may experience days of persistent vomiting after cannabis use.
Interestingly, taking a hot bath or shower can temporarily ease the symptoms for some people.
Discontinuing cannabis use often resolves CHS.
During the COVID-19 pandemic (2020–2021), public health researchers James Swartz and Dana Franceschini observed a notable rise in CHS cases across U.S. emergency departments. Analyzing about 806 million ER visits from 2016 to 2022, their work represents only the third national effort to examine CHS trends in the country.
Most CHS patients were around 30 years old, with slightly more women than men affected. Regional patterns showed higher prominence in the West and Northeast compared with the South.
Whether the increase reflects more frequent cannabis use or simply better recognition remains unclear.
Swartz and Franceschini suggest that the pandemic’s stress, isolation, and potential uptick in cannabis use may have contributed to the rise. Others argue that the rising percentage of CHS diagnoses could stem from greater awareness and publication bias about a newly recognized syndrome, rather than a true surge in cases.
Historically, CHS has been labeled as rare but meaningful and sometimes misunderstood. In some case reports, receiving a CHS diagnosis required up to 17 hospital admissions, and some patients were unfairly viewed as exaggerating symptoms.
Diagnosing CHS hinges on excluding other possible causes of vomiting. Cannabis use is a key diagnostic clue, yet some physicians may not ask about it, and some patients may be reluctant to share such information.
Experts acknowledge a paradox: CHS did not show a clear pre-2020 rise despite increasing cannabis legalization and the availability of high-potency products. This may reflect underdiagnosis or misclassification before the syndrome gained wider clinical recognition. The post-2020 uptick could indicate both greater exposure and heightened diagnostic vigilance.
Better diagnostic methods and more research are needed before CHS’s true rarity can be established.
This summary reflects findings published in JAMA Network Open.
