Cannabinoid Hyperemesis Syndrome (aka CHS) is a rare form of non-stop vomiting related to too much cannabis use.
Read about the history, prevalence, causes, and cures in this expert research review.
Leafly fully updated this post in December 2024
In 2004, doctors started to document a set of symptoms associated with a small segment of cannabis consumers. Patients, all with histories of heavy cannabis use, were coming into emergency rooms complaining about intense nausea, vomiting and temperature shifts that wouldn’t subside. Oddly, the patients all claimed that their symptoms could be temporarily relieved by taking hot showers or baths – but they couldn’t stay in hot water all day and needed solutions.
Doctors named the condition Cannabinoid Hyperemesis Syndrome (abbreviated as CHS), but had very little information on why it happened or how to treat it. It was considered to be a very rare condition.
Now, 20 years later, cases of CHS have risen dramatically in areas with legal cannabis access, and researchers have learned a lot more about what CHS is, who is likely to get it, and how to get it to stop.
What is Cannabinoid Hyperemesis Syndrome?
Cannabinoid hyperemesis syndrome (also known as cannabis hyperemesis syndrome, or CHS) is a condition associated with heavy, long-term cannabis use. Its acute “hyperemetic” phase is characterized by vomiting, nausea, severe gastrointestinal discomfort, temperature disturbances and compulsive bathing. This intense phase may be preceded by a period of milder symptoms like morning nausea, consistent urges to vomit, abdominal pain and diarrhea.
These symptoms can be severe and difficult to manage, seriously impacting someone’s quality of life and ability to function. Since these symptoms can cause dehydration, in rare uncontrolled cases it can even lead to death from kidney failure.
So far, the only known way to completely resolve symptoms of CHS is to stop all cannabinoid use.
Research on Cannabinoid Hyperemesis Syndrome
The earliest focused study on the cannabinoid hyperemesis phenomenon was in 2004, when Australian researchers noticed a commonality among patients experiencing cyclical vomiting symptoms: chronic cannabis use. Seven out of ten subjects who abstained from cannabis resolved their cyclical vomiting symptoms; the other three participants refused to abstain and their symptoms continued.
When first discovered in 2004, the condition was considered rare. But over the next decade, more cases of CHS started to show up in the medical literature.
- In 2009, a 22-year old cannabis consumer exhibited CHS symptoms in a U.K. case study. His symptoms resolved following cannabis cessation.
- Two more cases in 2009 that matched CHS criteria were recorded. Severe symptoms improved following 24 to 48 hours after cannabis cessation.
- A 42-year old chronic cannabis user was CHS symptom-free 3 months after his diagnosis, according to a 2014 U.K. case study.
The appearance of cannabinoid hyperemesis syndrome in medical literature was rare for two reasons:
- (a) the condition had only recently been acknowledged and named, and
- (b) CHS – as a result – is likely to have been misdiagnosed as cyclical vomiting syndrome (CVS). Though rarely seen in study papers, personal stories were beginning to bubble up in media reports and by word-of-mouth.
Soon Facebook groups dedicated to CHS started to appear as well, with thousands of people who claimed they had these same symptoms.
While CHS is usually triggered by heavy THC use, synthetic cannabinoids, CBD products (which may contain higher levels of THC than labeled), and Epidiolex (a pharmaceutical with 98% pure CBD) have all been reported to trigger CHS in some.
Prevalence and diagnosis of CHS
Over the last decade, the prevalence of those diagnosed CHS significantly increased. CHS is most commonly reported in North America, but the exact numbers are still difficult to estimate. One study from Northern California found that CHS diagnoses increased by 134–175 % each year over the last 11 years. Another study based on data from an ER in New York City suggested the numbers for CHS in the USA could be anywhere from 350,000 to 2.75 million people. (For context, Statista states that there are roughly 43.6 million past-month weed smokers in the US.)
Still, getting diagnosed with CHS isn’t always simple. One study found a median time of 8 years from symptoms beginning to diagnosis – with some patients going up to 21 years with symptoms before a CHS diagnosis. Patients in that study went to the ER an average of 22 times for their symptoms before getting a diagnosis.
While more people are becoming aware of the condition, there are several factors that can delay diagnosis and treatment. For one thing, it is often misdiagnosed as other conditions, delaying treatment and recommendations for cannabis abstinence. This can be a costly process, with one study suggesting costs as high $95,000 in 2012 to go through all the medical visits and testing that happened prior to the diagnosis.
In other cases, patients may be misdiagnosed with CHS when they DO actually have another condition. For instance, one case study describes a patient who was diagnosed with CHS when she actually has a rare and often deadly condition called superior mesenteric artery syndrome. This delayed her treatment and risked her life.
These cases highlight the importance of finding better ways to distinguish CHS from other conditions that manifest in similar ways.
Still, even when accurately diagnosed, many patients do not believe that cannabis is at the root of their problem, and may delay stopping cannabinoids for some period of time while they attempt to find other causes of their condition.
What are Cannabinoid Hyperemesis Syndrome signs and symptoms?
Researchers have proposed CHS is characterized by three phases.
Prodromal Phase
Typically months or years before exhibiting severe cyclical vomiting symptoms, the patient experiences:
- Morning sickness
- Abdominal pain and discomfort
- Nausea and fear of vomiting
Appetite is typically unaffected during this phase, but researchers note that consumers tend to administer more cannabis as a nausea remedy.
While often excluded from this list, one study found that 23% of presentations involve diarrhea at this stage, increasing the potential for misdiagnosis as gastroenteritis.
Importantly, the patient must be a (usually frequent) cannabis user during this time for the CHS diagnosis to fit.
Hyperemetic Phase
The acute phase of the illness is characterized by an intensification of effects and unique behaviors:
- Persistent nausea and vomiting that can last for hours at a time
- Frequent retching, up to five times an hour
- Abdominal pain
- Weight loss
- Dehydration
- Habitual bathing and/or showering
Why the compulsive bathing and showering? Hot temperatures are known to relieve the nausea and vomiting associated with CHS. The reasons why are not well developed, but researchers propose that “hot bathing may act by correcting the cannabis-induced equilibrium of the thermoregulatory system of the hypothalamus.”
Recovery Phase
After halting cannabis use patients typically recover in a matter of days, weeks, or months. Nausea ceases, appetite resumes, body weight is regained, and bathing/showering regimen returns to normal.
Why would cannabis cause the symptoms that characterize CHS?
Many wonder why or how cannabis could cause these symptoms. After all, cannabis usually helps people feel less nauseous. But there are a number of theories about why cannabis could lead to CHS.
Early theories from suggested that activation of CB1 receptors (primarily by THC) may result in the following gastrointestinal actions:
- Inhibition of gastric acid secretion
- Lower esophageal sphincter relaxation
- Altered intestinal motility
- Visceral pain
- Inflammation
- Reduces gastric motility
- Delays gastric emptying
These mechanisms suggest that perhaps when THC is consumed heavily and over a long period of time, it may exert anti-emetic properties on the brain, but cause nausea via its effect on the gut.
THC is also known for having biphasic effects, which means it can cause two opposite effects at different doses.
THC is also known for having biphasic effects, which means it can cause two opposite effects at different doses. Some have suggested that high doses might cause the anti-emetic effects to flip into a pro-emetic syndrome.
Additionally researchers have pointed to overstimulation of CB1 or TRPV1 receptors – leading the body to reduce the amount of those receptors – as a possible mechanism for CHS. While these are all just theories, they make sense with what we know about cannabis and its impact on the human body.
What has never been clear was why only some heavy users of cannabis seem to be affected.
Still, recent studies have opened up a new possibility—that genetics are the reason why CHS hits some cannabis consumers but not others.
CHS is likely genetically heritable
Cannabis researcher Ethan Russo recently published a new study which found 5 statistically significant mutations in CHS patients. Importantly, they are all mutations that are not found in frequent cannabis users without CHS symptoms. These genes impact the TRPV1 receptor, dopamine receptors, and the enzyme CYP2C9 (which is responsible for metabolising THC in the liver). Each of these genes impact some aspect of cannabinoid metabolism or CHS symptomatology—suggesting that this isn’t a coincidence.
it’s likely that CHS is a heritable condition that only occurs when someone with these genes uses cannabis frequently for a long period of time.
Based on this data, it’s likely that CHS is a heritable condition that only occurs when someone with these genes uses cannabis frequently for a long period of time.
Perhaps even more importantly, these genetic differences are also a risk factor for a range of other conditions – including addiction, chronic pain, depression, anxiety, coronary artery disease, dementia and type 2 diabetes. This means that getting diagnosed could be key to preventing other health risks for this vulnerable population.
Debunked CHS Theories
What’s unlikely is that CHS is attributable entirely to pesticide contamination, as some cannabis advocates have suggested. While pesticides like neem oil can cause poisoning, the common effects of that poisoning do not line up with CHS symptoms.
Another misconception is that CHS is a subtype of cyclic vomiting syndrome (CVS). While these are similar conditions symptomatically, they have very different root causes. CVS is actually a type of migraine condition that usually appears during infancy or childhood and develops into more classic migraine symptoms later on. Studies on CHS on the other hand have found the average age of onset to be 32 years old, and does not seem to be related to migraine.
To add to this, the genetic markers associated with it, were not found in the CHS cohort from Russo’s study.
Treatment for CHS
More research is needed to develop treatments for CHS. Currently a wide range of pharmaceutical treatments have been attempted including triptans, antiemetics, anxiolytics, NK-1 receptor antagonists, antipsychotics, sedatives in general, and various analgesic / anti-inflammatory medications. Most have had little benefit.
Some report that reducing external stimuli in a quiet dark room, hot water bathing, or using capsaicin cream helps temporarily reduce symptoms.
the only clear and universally effective way to get rid of CHS symptoms is to entirely stop cannabis.
Ultimately though, the only clear and universally effective way to get rid of CHS symptoms is to entirely stop cannabis. It can take days to months to resolve but most patients recover once they are fully off of any kind of cannabinoid. Unfortunately, many relapse into cannabis use, and then their CHS symptoms return.
If you are experiencing CHS symptoms, the best thing you can do is to stop cannabis use and seek medical care immediately. Dehydration from vomiting can be fatal, so these symptoms should be taken seriously.
