CHS stands for cannabinoid hyperemesis syndrome, a condition that causes severe, repeated episodes of nausea and vomiting in people who use cannabis frequently over a long period. It’s a paradox that catches many people off guard: cannabis is widely known for relieving nausea, yet in heavy, long-term users it can trigger the opposite effect. CHS has become increasingly recognized in emergency departments as cannabis use has grown more common and more potent products have become available.
What Causes CHS
Your body has a built-in system of receptors that respond to compounds in cannabis. In occasional or moderate users, activating these receptors tends to suppress nausea. But with chronic, heavy use (typically daily or near-daily for more than a year), those receptors become overstimulated. Over time, this disrupts the body’s natural ability to regulate nausea and vomiting, essentially flipping the anti-nausea effect on its head.
Cannabis also affects a separate system of pain-sensing receptors in the peripheral nervous system. These receptors play a role in gut motility and the sensation of nausea. Chronic exposure to cannabinoids alters how both receptor systems function, and the combination appears to be what makes CHS so distinctive and so resistant to standard anti-nausea medications.
The Three Phases of CHS
CHS doesn’t hit all at once. It follows a recognizable cycle of three phases that can repeat for months or years if cannabis use continues.
Prodromal Phase
The earliest sign is usually morning nausea without actual vomiting, along with vague abdominal discomfort. Many people don’t connect these symptoms to cannabis at this stage. Some even increase their cannabis use thinking it will help the nausea, which can accelerate the progression.
Hyperemetic Phase
This is the crisis stage. Nausea becomes intense and unrelenting, with episodes of vomiting that can last for hours or days. The vomiting typically doesn’t respond to standard anti-nausea medications. Abdominal pain is common, and dehydration can become serious enough to require emergency care. One of the most recognizable behaviors during this phase is compulsive hot bathing or showering, sometimes for hours at a time, because the heat provides temporary relief from the nausea.
Recovery Phase
Once vomiting subsides, the person returns to feeling normal. The urge to take hot showers fades. This phase can last weeks to months, even if the person continues using cannabis, before the cycle starts again and symptoms return.
How CHS Is Diagnosed
There’s no blood test or scan that confirms CHS. Diagnosis is based on a pattern: episodic vomiting that resembles cyclic vomiting syndrome, a history of heavy cannabis use for more than a year (at least four times per week on average), and symptom relief after sustained cannabis cessation.
Distinguishing CHS from cyclic vomiting syndrome (CVS) is one of the biggest challenges. The two conditions look nearly identical in terms of symptom pattern, timing, and severity. Even the compulsive hot bathing that’s considered a hallmark of CHS shows up in roughly half of CVS patients who don’t use cannabis at all. Some researchers believe CHS may actually be a subset of CVS rather than a completely separate disease. The key differentiator is the cannabis use history: if someone uses cannabis fewer than four times a week, CHS is unlikely to be the right diagnosis.
A confirmed diagnosis often requires stopping cannabis for at least six months to see if the episodes resolve. That timeline can feel frustratingly long, but shorter periods of abstinence aren’t always enough to rule CHS in or out.
What Treatment Looks Like
During an acute vomiting episode, emergency treatment focuses on replacing fluids and electrolytes lost from prolonged vomiting. Standard anti-nausea medications often fail in CHS, which is part of what makes it so difficult to manage in the moment. Recent evidence suggests that a specific type of medication that blocks dopamine receptors in the brain’s vomiting center is more effective than the usual anti-nausea drugs. In some cases, patients who haven’t responded to anything else see their nausea, vomiting, and abdominal pain resolve within an hour of receiving this treatment.
The only reliable long-term solution is stopping cannabis use entirely. The hyperemetic phase will continue to recur as long as cannabis use continues. Many people cycle through multiple emergency visits before making this connection, partly because the idea that cannabis causes vomiting feels counterintuitive, and partly because the recovery phase creates a window where everything seems fine.
Risks of Repeated Episodes
CHS episodes aren’t just miserable; they can be medically dangerous. Prolonged, severe vomiting leads to dehydration, which strains the kidneys and can cause dangerous shifts in electrolyte levels. Repeated vomiting also damages the esophagus and can weaken the sphincter muscle between the esophagus and stomach. People who go through many cycles before getting diagnosed sometimes accumulate significant emergency department visits and unnecessary testing for other gastrointestinal conditions.
Why CHS Is Increasingly Common
CHS was first described in the medical literature in 2004, and for years it was considered rare. That’s changed substantially. Cannabis potency has increased dramatically over recent decades, legal access has expanded, and daily use has become more normalized. Higher-potency products like concentrates and edibles deliver larger doses of cannabinoids, which may accelerate the receptor overstimulation that drives CHS. The condition is still likely underdiagnosed, especially in states and countries where patients may be reluctant to disclose cannabis use to their doctors.
If you or someone you know uses cannabis regularly and has been dealing with unexplained episodes of severe nausea and vomiting, particularly with the telltale relief from hot showers, CHS is worth considering as the cause.