As cannabis use becomes more common across the United States, doctors are raising concerns about a serious but often overlooked side effect linked to frequent use. Twenty-four states now allow recreational marijuana, and millions of Americans report using it regularly. But hospitals are seeing a rise in patients with intense nausea, stomach pain, and repeated vomiting—all tied to a condition known as cannabis hyperemesis syndrome (CHS).

CHS affects people who use cannabis daily or nearly every day over long periods. Health specialists say the episodes usually begin within a day of the most recent use and can last for several days. Many patients experience these attacks multiple times a year, often severe enough to require emergency care.

The World Health Organization recently added CHS to its official list of medical conditions, allowing researchers to better track cases. Experts hope this will lead to clearer data on how long-term cannabis use impacts the digestive system.

Beatriz Carlini, a researcher at the University of Washington, says the new classification helps physicians and public health officials better understand the scope of the problem. She notes that many patients end up in the emergency room several times before receiving the correct diagnosis, since CHS can resemble food poisoning or the flu.

Doctors are still studying why some people develop the condition while others do not. According to emergency physician Dr. Chris Buresh, there appears to be an individual threshold for vulnerability. Even people who have used cannabis for years without issues may suddenly develop symptoms, and in some cases, even small amounts can trigger vomiting.

Researchers emphasize that anyone who uses cannabis regularly and experiences repeated bouts of severe nausea should discuss the possibility of CHS with a healthcare professional.