CHS, or cannabinoid hyperemesis syndrome, is a condition where long-term, frequent cannabis use triggers recurring episodes of severe nausea, vomiting, and abdominal pain. It typically develops after at least one year of heavy use, often longer, and the only reliable way to stop it permanently is to quit cannabis entirely. The condition is increasingly recognized as cannabis use has become more widespread, but it’s still frequently misdiagnosed because many people and even some doctors don’t associate marijuana with vomiting.
How CHS Feels
The hallmark symptoms are persistent nausea (often worst in the morning), intense and repeated vomiting that can happen up to five times an hour, and abdominal pain or discomfort. Many people also develop a fear of vomiting and lose their appetite. These episodes come in cycles: you might feel fine for weeks, then suddenly enter a stretch of relentless nausea and vomiting that sends you to the emergency room.
One of the most distinctive features of CHS is compulsive hot showering or bathing. During an episode, many people discover that standing under very hot water is the only thing that brings temporary relief. The likely explanation is that the heat causes blood vessels in the skin to dilate, redirecting blood flow away from the gut and calming the nausea. It may also involve THC’s direct effects on the brain’s temperature-regulation center. Not everyone with CHS develops this bathing behavior, but it’s common enough that doctors use it as a diagnostic clue.
The Three Phases
CHS tends to move through a recognizable cycle of three stages.
The prodromal phase comes first. You may notice early morning nausea without actually throwing up, along with vague abdominal discomfort. This phase can last weeks or months, and many people continue or even increase their cannabis use during it, sometimes believing marijuana will help settle their stomach.
The hyperemetic phase is the crisis point. Nausea becomes constant and vomiting becomes severe and difficult to control with standard anti-nausea medications. Abdominal pain is common. This is the phase that typically drives people to seek emergency care. It can last hours to days.
The recovery phase follows, where symptoms gradually fade and you return to feeling normal. This phase can last weeks to months, even if you continue using cannabis. But the cycle eventually restarts, and the hyperemetic phase returns. Each cycle tends to repeat every few weeks to months.
Why Cannabis Causes Vomiting
This seems contradictory, since cannabis is well known for reducing nausea. The explanation lies in a dose-dependent flip. At low doses, THC activates receptors in the brain that suppress nausea. But with chronic, heavy use, those same receptors become desensitized. They essentially stop responding normally, and the signaling pathways that regulate nausea and vomiting in the gut and brain become disrupted.
THC also interacts with pain and heat-sensing receptors found throughout the digestive tract and the brain’s vomiting center. These receptors sit close to the cannabinoid receptors, and chronic overstimulation appears to throw the whole system off balance. Genetics may play a role too: a small study identified mutations in five genes involved in pain signaling, dopamine processing, and cannabinoid metabolism that could make certain people more vulnerable to CHS.
How CHS Is Diagnosed
There’s no blood test or scan for CHS. Diagnosis is based on your history and symptoms, using criteria that require at least three months of symptoms with onset at least six months before diagnosis. The key factors doctors look for are:
- Heavy, long-term cannabis use of more than one year, typically four or more times per week
- Cyclical vomiting episodes with at least three episodes per year
- Symptom relief after quitting cannabis for a sustained period
- Compulsive hot bathing during episodes (present in most but not all cases)
CHS is often confused with cyclic vomiting syndrome (CVS), which looks almost identical on the surface. Both cause recurring bouts of severe nausea and vomiting with symptom-free stretches in between. The critical difference is the cannabis connection. CVS is more commonly associated with migraines, autonomic dysfunction, and psychiatric conditions. Interestingly, up to 48% of CVS patients also seek relief in hot showers, compared to about 72% of CHS patients, so that behavior alone doesn’t distinguish the two. Since cannabis legalization has expanded, the odds of cannabis use among people diagnosed with CVS have roughly tripled, which means some CVS diagnoses may actually be unrecognized CHS.
Treatment During an Episode
Standard anti-nausea medications often don’t work well for CHS. In a clinical trial comparing treatments for acute CHS episodes, a specific anti-psychotic medication outperformed the most commonly used anti-nausea drug. Patients who received it had significantly better symptom relief, needed fewer additional medications (31% needed rescue drugs versus 59%), and left the emergency department about 2.5 hours sooner on average.
Another option that has shown promise is capsaicin cream, the same ingredient that makes chili peppers hot. Applied to the upper abdomen three times daily, it activates the same heat-sensing receptors that hot showers stimulate, providing relief without the need to stand under running water for hours. Higher concentrations (0.1%) appear more effective than lower ones. In reported cases, patients experienced near-complete symptom resolution within 24 hours of starting it.
The Only Long-Term Fix
Quitting cannabis entirely is the only proven way to stop CHS from recurring. After stopping, the vomiting cycle typically takes one to three months to fully resolve. That recovery period can feel long, especially since many people with CHS have used cannabis daily for years and may experience withdrawal symptoms on top of lingering nausea.
Resuming cannabis use, even after months of feeling fine, restarts the cycle. This is one of the most frustrating aspects of CHS for people who use cannabis to manage anxiety, pain, or sleep. But the condition does not improve with reduced use or switching to different strains or products. The receptors need time without any THC exposure to reset, and reintroducing it at any level carries the risk of triggering the syndrome again.