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Why are more cannabis users landing in the hospital with severe vomiting?

Chronic cannabis use is increasingly linked to recurring bouts of vomiting, now officially classified as cannabis hyperemesis syndrome. A new process helps doctors identify cases more consistently. In addition, it provides researchers with a clearer picture of how often it occurs.

Patients often resist the diagnosis, and the condition’s causes remain murky. Relief can come from unusual sources like hot showers or capsaicin cream.

Over the past ten years, emergency departments in the U.S. have seen a steady rise in patients seeking help for abdominal pain and episodes of intense or long-lasting vomiting. What these cases often share is chronic cannabis use.

Until recently, clinicians lacked a standardised way to document this condition. Now they have a diagnostic code for “cannabis hyperemesis syndrome,” a gastrointestinal disorder that begins within 24 hours of the most recent cannabis use and can continue for several days. Those who experience it typically face these symptoms three or four times each year.

From 1st October 2025, the World Health Organisation has added a formal entry for the condition to its International Classification of Diseases manual (ICD-10, currently). In the U.S., the Centers for Disease Control and Prevention (CDC) has adopted the new code, R11.16, into U.S. diagnostic systems.

The code offers several benefits, says the University of Washington School of Medicine. Clinicians can now document the syndrome with a single, specific billing code instead of relying on multiple, less precise ones. Having the code appear in a patient’s medical record also helps providers recognise repeat episodes during future visits.

An important gain is improved data reliability. Investigators such as Beatriz Carlini can now track cases more accurately and look for patterns that were previously difficult to identify.

In studying addiction and other public health concerns, medical researchers have three sources of data: what clinicians state, what people in the communities say, and what health records infer.

The new code for cannabis hyperemesis syndrome supplies important hard evidence on cannabis-adverse events, which physicians tell us is a growing problem.

Although hospitals are seeing more patients with these symptoms, many providers are still unfamiliar with the condition because it has only recently been defined.

Even after an accurate diagnosis, some patients struggle to accept that cannabis is the source of their severe nausea and vomiting. Cannabis is widely known for easing nausea in people undergoing chemotherapy or living with chronic conditions such as HIV and migraines, which adds to the confusion.

Researchers are unsure if increased rates of sickness are related to the greater general availability of cannabis or the higher THC potency of some products or something else.

In addition, treating the condition is difficult. Standard anti-nausea medications often do not work reliably, he said, which sometimes forces clinicians to turn to second and third-line options such as Haldol, a medication more commonly used for psychotic episodes.

Some individuals find limited relief through capsaicin cream, an over-the-counter analgesic that creates a warming sensation. According to Buresh, some patients apply it to their abdomen during episodes. Hot showers are also widely reported as helpful.

Several factors can slow recovery. Because the syndrome appears intermittently, some cannabis users may assume a recent episode was unrelated and continue using the substance without immediate problems, only to suddenly become severely ill again. For those who accept the diagnosis and try to stop cannabis use to ease their symptoms, addiction can make abstinence difficult.