What Is Cannabinoid Hyperemesis Syndrome?
I can still recall the first time someone told me about a bizarre and peculiar syndrome that seemed to cause vomiting when certain individuals used cannabis.
As a cannabis educator, I found this information confusing when much of the education I provide patients focuses on evidence of cannabis being used as an antiemetic, something that is known to help stop vomiting and nausea. You can imagine my surprise when learning of this odd condition called Cannabinoid Hyperemesis Syndrome, a cyclic vomiting syndrome caused by high THC cannabis use.
Even as a cannabis educator and informed patient, years later, I still find this condition perplexing. How can cannabis, a supplement which is known for helping to ease nausea and suppress vomiting, have such a paradoxical effect in some patients? While it is still unclear what the exact cause of CHS is, we do know that as cannabis use increases across the country, so do the reports of its inconsistent effects as well, like those associated with CHS.
To help understand this paradoxical syndrome, we will take a look at the differences between similar cyclical vomiting syndrome (CVS), CHS, and their respective symptoms; discuss current diagnostic testing, treatment options, and cures; and finally look at what the research shows, including the most recent study showing hope for possible genetic testing in the future to determine if a patient has a predisposition to this relatively new syndrome.
What is Cannabinoid Hyperemesis Syndrome?
First reported in Australia in 2004, Cannabinoid Hyperemesis Syndrome is a form of cyclical vomiting syndrome that seems to be triggered by long-term and excessive cannabis use. It is characterized by cyclical and extreme nausea, vomiting and abdominal pain following daily or weekly cannabis use usually for a year or more.
Another major indicator of this syndrome and a part of the CHS cycle includes hot water bathing in an attempt to provide symptom relief. [1, 2] Although it is currently unclear how many people are affected by CHS due to all the unknowns, a study published in 2018 estimates that approximately 2.75 million people may experience from CHS in the U.S. annually.  In comparison, the World Health Organization estimates that 147 million people currently use cannabis annually worldwide, bringing the estimate of those who experience CHS to 1.87% of all cannabis users.
CHS vs. CVS
Although Cannabinoid Hyperemesis Syndrome is a form of Cyclic Vomiting Syndrome with similar symptoms, it does differ slightly. Let’s first take a look at what CVS looks like.
Cyclic Vomiting Syndrome
Cyclic Vomiting Syndrome by definition is a functional gastrointestinal disorder that is characterized by severe vomiting, with usually 3 or more recurrent episodes, that doesn’t seem to have any apparent cause. Some of the most common CVS symptoms include:
- Extreme nausea
- Repeated episodes of extreme vomiting
- Abdominal Pain
Cyclic Vomiting Syndrome is difficult to diagnose as there is currently no specific test that determines if a patient has it or not. First, other conditions must be ruled out followed by a series of tests. It is important to note that there is currently no known cure for Cyclic Vomiting Syndrome.
Now let’s take a look at CHS Symptoms and see how they compare to CVS.
Cannabinoid Hyperemesis Syndrome
CHS symptoms seem to follow a more cyclical progression than CVS. Cannabinoid Hyperemesis Syndrome is also usually preceded by long-term cannabis use and displays the following symptoms:
- Extreme nausea
- Repeated episodes of extreme vomiting
- Abdominal pain
- Hot water bathing
One big difference between CVS and CHS is the exposure to prolonged and excessive cannabis use as well as the hot water bathing (though, interestingly, according to recent research the relief brought by hot water bathing for those with CHS may bode well for those with CVS).
So, how does a patient seek a diagnosis?
Although there is no definitive test to determine if a patient has CHS, a systematic review  which included 183 abstracts, identified the following as the main diagnostic characteristics:
- History of regular cannabis use (100%)
- Cyclic nausea and vomiting (100%)
- Resolution of symptoms after stopping cannabis (96.8%)
- Compulsive hot baths with symptom relief - 92.3%
- Male predominance - 72.9%
- Abdominal pain - 85.1%
- At least weekly cannabis use - 97.4%
Since there are still so many unknowns when discussing CHS, it often goes misdiagnosed.
Due to the fact that CHS is still misunderstood and because there is no definitive test to determine if a patient has CHS, it often goes misdiagnosed initially. CHS is most commonly simply misdiagnosed as CVS, cyclic vomiting syndrome, because of all the similarities that we’ve just read about. This confusion is amplified when patients diagnosed with CVS use cannabis regularly. This review highlights the difficulty and confusion that arises when diagnosing CHS, leading researchers to believe that the current estimate of people suffering from CHS may be larger than what is currently reported. Since diagnosing CHS is not always easy and concise, many patients wind up with outrageous medical bills due to multiple tests, hospital visits, and emergency visits. The median spend for emergency visits and hospital admissions for the patients in this systematic review was documented at over $95k. 
What Is The Course Of CHS?
According to studies, Cannabinoid Hyperemesis Syndrome has 3 distinct phases: the prodromal, the hyperemetic, and the recovery phase. [5,6] These phases are briefly described as follows:
The Prodromal Phase
This is the first phase of CHS in which one may suffer from:
- Severe nausea,
- Increased thirst
Research shows that this phase can last for several weeks, months, or even years before moving into the next phase, the hyperemetic phase.
The Hyperemetic Phase
The second phase of CHS is where patients typically suffer from:
- Extreme nausea,
- Abdominal pain
Some patients report vomiting up to 5 times per hour. This is also the stage where patients seem to begin the hot shower and bathing behavior. During this phase, patients become more prone to dehydration, liver failure, and adrenal failure.
The Recovery Phase
This is the final phase of CHS. Research shows that it can take weeks or months for a patient to fully recover following cannabis use cessation.
While research shows that CHS is not permanent, it is important to note these phases follow a cyclical pattern which will continue unless a patient fully ceases cannabis use.
CHS Treatments and Cures
While treatment for CHS is dependent upon which phase of the cycle patients find themselves, some of the most common treatments include [1,6]:
- Cannabis Cessation - this has been shown to be the only long-term cure for CHS
- Hot baths / showers
- IV fluids
- Western pharmaceuticals, in the form of Benzodiazepines
- Topical capsaicin cream
- Avoiding narcotic medications
Breaking it down a bit more, if a patient finds themselves in the hyperemetic phase, hot baths or showers may be the best treatment for symptom relief. Common western pharmaceuticals, such as benzodiazepines and antipsychotics, seem to also be effective during the hyperemetic phase.  If trying to avoid future episodes of CHS, the main treatment and only known cure seems to be cannabis cessation.
What Causes CHS?
Although it is still unclear why some patients experience CHS symptoms and others don’t, high THC cannabis use for a year or more has been linked to being one of the main causes of CHS. This is one of the examples of the biphasic nature of cannabis in regards to CHS symptoms from one patient to the next. While the causes of CHS are still being studied, new research shows promising hope for patients looking for a more definitive test and timely diagnosis.
Most research has linked CHS with long-term and excessive cannabis use, however, a recent study published in July 2021 shows that CHS may be a result of a genetic mutation, suggesting that some patients may be genetically predisposed to CHS. Although the total number of patients studied was smaller than scientists would have desired, this study recorded the results of the largest patient set to date on the topic: 205 patients and 54 controls, while a reduced group of 28 patients and 12 controls opted for genomic testing.
The results indicate that scientists may be on the path to identifying genetic markers for CHS. In this study, 5 mutations were identified from a small dataset which may show promise for identifying at-risk individuals and help to eliminate more expensive testing by diagnosing through exclusion. This study suggests that CHS may in fact be a rare genetic disease that is revealed after excessive THC use as opposed to a functional GI disorder.  It is projected that a CHS genomic test will be available for gastroenterologists and hospital emergency departments by the end of summer 2021.
“These important preliminary findings contribute to the growing body of knowledge, stimulate additional investigation, help elucidate the pathophysiology of CHS and, ultimately, direct future treatment,” says chief investigator Ethan Russo, MD. Dr. Russo adds, “Screening patients for this condition will help obviate the need for repetitive hospitalizations, expensive and invasive diagnostics.”
As cannabis becomes more widespread, it’s important to acknowledge the abnormalities that some patients experience with long-term and excessive cannabis use, like those associated with Cannabinoid Hyperemesis Syndrome. Although cannabis is generally well-known for its anti-nausea and antiemetic properties, CHS shows us that there are always exceptions. Moving forward, it is likely we will see CHS reports increase as more people explore cannabis as an alternative way of healing and as more research is conducted. This is why, when beginning a cannabis regimen, it is always important to start low and go slow with dosing, and to track and notate your experiences with cannabis. If you are concerned that you or someone you know is suffering from CHS, it is important to contact your doctor immediately.
 - Sorensen, Cecilia J et al. “Cannabinoid Hyperemesis Syndrome: Diagnosis, Pathophysiology, and Treatment-a Systematic Review.” Journal of medical toxicology : official journal of the American College of Medical Toxicology vol. 13,1 (2017): 71-87. doi:10.1007/s13181-016-0595-z
 - Sun, Shusen, and Anthony E Zimmermann. “Cannabinoid hyperemesis syndrome.” Hospital pharmacy vol. 48,8 (2013): 650-5. doi:10.1310/hpj4808-650
 - Habboushe, Joseph et al. “The Prevalence of Cannabinoid Hyperemesis Syndrome Among Regular Marijuana Smokers in an Urban Public Hospital.” Basic & clinical pharmacology & toxicology vol. 122,6 (2018): 660-662. doi:10.1111/bcpt.12962
 - Russo EB, Spooner C, May L, Leslie R, Whiteley VL (2021) Cannabinoid hyperemesis syndrome survey and genomic investigation, Cannabis and Cannabinoid Research X:X, 1–9, DOI: 10.1089/can.2021.0046.
 Galli, Jonathan A et al. “Cannabinoid hyperemesis syndrome.” Current drug abuse reviews vol. 4,4 (2011): 241-9. doi:10.2174/1874473711104040241
 - Marieka V. DeVuono and Linda A. Parker. “Cannabinoid Hyperemesis Syndrome: A Review of Potential Mechanisms” Cannabis and Cannabinoid Research.June 2020.132-144.http://doi.org/10.1089/can.2019.0059 Published in Volume: 5 Issue 2: June 5, 2020 Online Ahead of Print:February 11, 2020