As more US states legalize cannabis, scientists are warning regular users about a disturbing side effect sending people to the hospital: cannabis hyperemesis syndrome (CHS). This condition, seen mostly in chronic users who consume cannabis daily or near-daily, causes intense nausea, abdominal pain, and prolonged vomiting — symptoms severe enough to trigger repeated emergency room visits.

CHS usually appears within 24 hours of the last use and can last for several days. Many doctors still misdiagnose it as stomach flu or food poisoning, leading patients to return to the ER multiple times before getting the correct diagnosis. The WHO has now officially listed the condition, helping researchers track cases more accurately.

Medical experts emphasize that the threshold for developing CHS varies widely. Some people experience it even after small amounts, while others may use cannabis for decades without issues. Researchers hope that continued study will reveal why certain users suddenly become vulnerable.

With hospital visits rising, health professionals urge chronic cannabis users to take unexplained vomiting seriously — and seek medical help if symptoms repeat.