What Is Cannabinoid Hyperemesis Syndrome?

Published on August 10, 2016 · Last updated January 25, 2021

I used cannabis for nausea without realizing it might actually have been the cause of it. Cannabinoid hyperemesis syndrome (also known as cannabis hyperemesis syndrome, or CHS) is a recently discovered, poorly understood condition theoretically caused by heavy, long-term cannabis use. Its acute “hyperemetic” phase is characterized by vomiting, nausea, severe gastrointestinal discomfort, and compulsive bathing, although it may be preceded by a period of milder symptoms like morning nausea, consistent urges to vomit, and abdominal pain.

When I read about this condition in a 2011 study from Temple University, I nearly fell out of my chair. I’ve been using cannabis medicinally for the last five years to treat morning sickness, nausea, and intestinal pain. A conversation with an ex came to mind. He used to antagonistically pose theories that cannabis might be what’s causing the problems, to which I would respond with a heated and defensive, “Cannabis is the only thing that helps, why would it be causing it?”

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Fast-forward one year to a discussion with my budtender who recently experienced the acute phase of the condition. As per her doctor’s recommendation, she set cannabis aside and within a few weeks, she made a full recovery. My friend’s symptoms were so much more severe than mine, it never occurred to me that I might be experiencing early stages of the same condition.

In fact, it took a long, hard look at the research for me to admit that the condition might even exist at all.

Research on Cannabinoid Hyperemesis Syndrome

The earliest focused study on the cannabinoid hyperemesis phenomenon appears to be 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.

Small case studies surfaced in the years following, demonstrating similar patterns:

  • 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 is rare for two reasons: (a) the condition has 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 are beginning to bubble up in media reports and by word-of-mouth.

I asked a number of doctors to share any cannabinoid hyperemesis syndrome patient information they had on hand, but it seemed that cannabis doctors were the only ones even privy to the condition at all. With 33 million Americans consuming cannabis, we can only hope that researchers and medical professionals will start to explore the many questions tied to this condition.

What Are Cannabinoid Hyperemesis Syndrome Signs and Symptoms?

Among patients diagnosed with cannabinoid hyperemesis syndrome, most tend to be “young adults with a long history of cannabis use,” according to the 2011 Temple study.

“In nearly all cases there is a delay of several years in the onset of symptoms preceded by chronic marijuana abuse. Daily marijuana use is characteristic and often reported as exceeding three to five times per day.”

As previously mentioned, researchers have proposed CHS be characterized by three phases.

1. 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.

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2. 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.”

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A 2014 review offers further explanation:

“The brain may react to changes in core body temperature due to the dose-dependent hypothermic effects of [THC]. Alternatively, the bathing behaviour may be a result of direct CB1 receptor activation in the hypothalamus by [THC] or another active compound and may not necessarily be a response to changes in core body temperature.”

3. Recovery Phase

After halting cannabis use (the only cannabinoid hyperemesis syndrome “treatment” option), 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.

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Why Would Cannabis Cause the Symptoms that Characterize CHS?

Though it will take a lot more research to evolve theory to fact, scientists at Temple University have a few leads on why cannabis might cause nausea and vomiting, upsetting what we’ve come to expect from our favorite anti-nausea remedy.

Cannabis may help us feel less nauseous by activating specific parts of the central nervous system, but what else might be happening in the gut itself? According to study authors from Temple University, 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 are all ingredients in a theory that is yet to be baked, but it presents an interesting paradox—that THC, when consumed heavily and over a long period of time, may exert anti-emetic properties on the brain, but cause nausea via its effect on the gut.

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The study also mentions a tangle of interactions between two secondary cannabinoids found in cannabis, CBD and CBG. They write:

“In animals the effect of CBD on toxin-induced vomiting displays a biphasic response with low doses producing an anti-emetic effect whereas higher doses enhance vomiting. Cannabigerol (CBG) is a non-psychotropic cannabinoid that behaves as an antagonist at both the CB1 and 5-HT1A receptors. This antagonism reverses the anti-emetic actions of low-dose CBD, which likely occurs at the 5-HT1A receptor. The pro-emetic properties of CBD (at higher doses) and CBG may play a role in the severe nausea and vomiting observed in patients with Cannabinoid Hyperemesis Syndrome.”

To reiterate, these are theories, not proven or substantiated results. These ideas pull from a patchwork of cannabis research – some from animal models and others from human trials. For this reason, it’s important to take this report and related case studies with a grain of salt.

Medical Professionals Are Still Skeptical on Cannabinoid Hyperemesis Syndrome

The proposals and theories put forth by researchers are compelling, but some medical professionals remain skeptical.

Authors of a 2006 review out of Australia criticize the original 2004 research that defined cannabinoid hyperemesis syndrome for poor study design and for misattributing increases in cannabis use to liberalized laws.

“Cannabis has been consumed for many centuries and is currently used by millions of people in many countries,” the authors wrote. “It is hard to believe that a distinctive syndrome caused by cannabis has never been noted before by users or clinicians.”

I spoke to a doctor from Green Leaf Health Care here in Seattle, wondering what his take on the research was. He, too, showed a degree of skepticism and offered another possible explanation.

“I have an additional theory which is that cannabis grown with chemicals is affecting people in various ways, [and] this may be one of them,” he said. “I’ve traveled through India and Asia extensively and know heavy long-term users without ever having issues regarding hyperemesis. Perhaps long term use and concentrated levels could produce these issues in certain susceptible individuals; however, I feel like it’s more of a chemical issue.”

The fact of the matter is, we don’t have enough research to show if or why cannabis is the cause of these symptoms. What we do know is that there are people out there who benefit from cutting back on their intake or ceasing altogether. It may be purely coincidence that my cutting back coincided with a gastrointestinal recovery. We can’t know why halting cannabis use helped my friend, or why she gets sick when she tries to resume. All we know is there’s a possibility of connection, and that successfully bridging such a connection holds important implications for those who use cannabis every day.

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Bailey Rahn
Bailey Rahn
Bailey is a senior content manager at Leafly, specializing in strains and health. She's spent 7+ years researching cannabis products, spreading patients’ stories, and exploring healthy ways of integrating cannabis into daily life.
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