Cannabinoid hyperemesis syndrome is a rare, newly discovered condition that causes ongoing nausea and vomiting. And though marijuana’s ability to ease nausea and vomiting is well-documented in scientific research, some scientists theorize that marijuana actually causes these symptoms in people with cannabinoid hyperemesis syndrome. So, can cannabis really cause nausea and vomiting for some people, even though it relieves these issues for other people? Below, we’re taking a closer look at this question as we go over what the current science says about cannabinoid hyperemesis syndrome.
What is Cannabinoid Hyperemesis Syndrome?
Cannabinoid hyperemesis syndrome, or CHS, is a rare condition that’s characterized by severe nausea, vomiting, gastrointestinal discomfort, and compulsive bathing in hot water. CHS is a newly observed, poorly understood syndrome. However, many scientists believe that CHS is a rare side effect of long-term, heavy marijuana use. This is because CHS appears to occur only in long-term daily marijuana users and also appears to be alleviated by the cessation of cannabis use.
Research on Cannabinoid Hyperemesis Syndrome
Cannabinoid hyperemesis syndrome was first observed in 2004 when an Australian doctor, J H Allen, noticed that many patients who had cyclical vomiting symptoms had something in common: long-term heavy cannabis use.
That same year, a team of Australian researchers conducted a study exploring the association noticed by Allen. They identified 19 patients that used cannabis heavily and had a cyclical vomiting illness. Out of these 19 patients, 5 declined to participate, while another 5 had to be excluded from the study, so there were 9 participants in total. The researchers found that “chronic cannabis use predated the onset of the cyclical vomiting illness” in all 9 cases. They also found that when 7 of the participants stopped using cannabis, their illness stopped. The participants who did not stop using cannabis continued to have symptoms. This led the researchers to conclude that “chronic cannabis abuse was the cause of the cyclical vomiting illness in all cases.”
In the years following this initial study, there were several small case studies with similar results. There are three case reports from 2009 in which patients exhibiting CHS symptoms made a full recovery after cannabis cessation. There’s also a case report from 2014 in which a 42-year-old long time cannabis user had CHS symptoms, then had no symptoms after ceasing to use cannabis for 3 months.
The 2004 study of 9 patients was the largest study on cannabinoid hyperemesis until 2012, when the Mayo Clinic did a case series with the objective of better understanding cannabinoid hyperemesis. This systematic review looked at 98 patients who exhibited cannabinoid hyperemesis symptoms at the Mayo Clinic between 2005 and 2010. The researchers found that 68% of patients used cannabis for more than 2 years before experiencing symptoms and that 95% of patients used cannabis more than once a week. The researchers noted that, alongside nausea and vomiting, abdominal pain (86%) and symptom relief with a hot shower or bath (91%) were the most common symptoms among participants. The researchers were able to follow up with 10 patients. They found that 7 out of 10 had stopped using cannabis and that 6 out of these 7 had noted “complete resolution of their symptoms.”
What Causes Cannabinoid Hyperemesis Syndrome?
Scientists have theorized that cannabinoid hyperemesis syndrome is caused by long-term heavy cannabis use. However, CHS is a rare syndrome that does not occur in all long-term heavy cannabis users. Researchers don’t know why CHS would occur in some long-term heavy cannabis users, but not in others.
Marijuana interacts with the body in complex ways that scientists don’t yet fully understand, which makes understanding the pathophysiology of CHS more challenging. On top of that, CHS is newly observed and understudied, so CHS research offers little insight on how marijuana could cause the syndrome. With that said, there are some theories on how marijuana may cause CHS in certain cases.
A 2020 review published in Cannabis and Cannabinoid Research examined the potential causes of cannabinoid hyperemesis syndrome. They looked at seven potential causes:
- A Dysfunctional Endocannabinoid System
- Acute Cannabinoid-Induced Nausea and Vomiting
- A Dysregulated Stress Response to Nausea and Vomiting
- Hypothalamus Pituitary Adrenal Axis Dysregulation
- Sympathetic Nervous System Dysregulation
- Dysregulation of TRPV1 Receptors in Endocannabinoid System
- Gut Motility Regulation
- Predisposing Factors (Such as Genetics and Mood Disorders)
- Cannabis Contamination
The authors of this review noted that the first of these potential causes, a dysfunctional endocannabinoid system (ECS), is generally considered the most likely cause of CHS. According the reviews, “the prevailing theory about how CHS develops is that extended activation of the CB1 receptor by prolonged exposure to tetrahydrocannabinol (THC) leads to desensitization and/or downregulation of the CB1 receptor and changes to endocannabinoid-related enzymes, resulting in endocannabinoid dysfunction.” To put that in layman’s terms, some scientists think that long-term heavy THC consumption may cause CB1 receptors, which are activated by THC and play a role in regulating nausea, to go haywire.
While endocannabinoid system dysfunction is considered a likely factor in CHS, we still don’t know if that’s the cause of the syndrome or if other factors may affect the disorder. We need far more research to understand how all of the potential causes of CHS may or may not affect who gets this rare syndrome.
What Are the Symptoms of Cannabinoid Hyperemesis Syndrome?
Scientists theorize that cannabinoid hyperemesis syndrome has three phases: a prodrome stage, an acute hyperemetic phase, and a recovery phase. Each of these phases is associated with different symptoms.
Prodromal Phase of CHS
The prodromal phase of an illness is the period of time after initial symptoms first appear, but before the illness is fully developed. It’s thought that the prodromal phase of cannabinoid hyperemesis syndrome may last for months or years.
The symptoms of the prodromal phase of cannabinoid hyperemesis syndrome include:
- Morning Nausea
- Abdominal Discomfort or Pain
- Urge to Vomit
- Fear of Vomiting
Hyperemetic Phase of CHS
The hyperemetic phase of cannabinoid hyperemesis syndrome occurs when the syndrome reaches its full onset. The symptoms of this phase include:
- Severe, Ongoing Nausea
- Repeated Vomiting
- Abdominal Pain
- Decreased Food Intake
- Weight Loss
- Compulsive Hot Bathing and/or Hot Showering
Frequently taking hot showers and baths is a hallmark symptom of CHS. This action occurs because it appears to reduce the nausea and vomiting that’s associated with the hyperemetic phase of CHS. Scientists don’t know why taking hot baths and showers alleviates vomiting and nausea in CHS, but one theory is that it’s because the heat sensation from the hot water is overriding nausea and pain sensation in the central nervous system.
Recovery Phase of CHS
The recovery phase of cannabinoid hyperemesis syndrome occurs when the affected person stops using marijuana. The symptoms of this phase include:
- Ease of Nausea and Vomiting Symptoms
- Return to Normal Eating Patterns
- Return to Normal Showering and Bathing Habits
How to Diagnose Cannabinoid Hyperemesis Syndrome
There’s no single test for cannabinoid hyperemesis syndrome. To diagnose the syndrome, a doctor needs to determine that a patient meets all four of these criteria:
- Long-Term Daily or Weekly Cannabis Use
- Abdominal Pain
- Severe, Ongoing Nausea and Emesis (Vomiting)
- Relief of Symptoms After Taking Hot Shower or Bath
In addition to looking for these symptoms, a doctor needs to rule out other possible causes of a patient’s symptoms before making a cannabis hyperemesis syndrome diagnosis. The symptoms of CHS can also be caused by other conditions, including serious or life threatening conditions. To rule out other potential causes of a patient’s symptoms, a doctor may order blood tests, electrolyte tests, urine analysis, a gastric emptying scan, a head or abdominal CT scan, or an endoscopy, among other things.
Is CHS New?
It’s probably more accurate to say that cannabinoid hyperemesis syndrome is newly observed or newly discovered than it is to say it’s new. It’s possible that CHS is new, but we can’t know for sure, since so little is known about why the adverse effects of CHS occur. Some scientists have theorized that CHS has been around for some time, but has been misdiagnosed as cyclic vomiting syndrome (CVS). CVS and CHS have very similar symptoms, so it would be easy for an emergency medicine provider or other healthcare practitioner to mistake one for the other.
Possible Complications of Cannabinoid Hyperemesis Syndrome
When left untreated, the persistent nausea and vomiting that people experience during the acute hyperemesis phase of CHS can lead to complications. Some of these complications may be more mild, while others may require urgent treatment and hospitalization. Examples of the complications of extreme, persistent nausea and vomiting include:
- Dehydration Symptoms, Such As:
- Muscle Spasms
- Muscle Weakness
- Kidney Failure
- Heart Rhythm Abnormalities
- Brain Swelling (In Rare Cases)
- Injury to Food Tube
- Tooth Decay
Possible Treatments for Cannabinoid Hyperemesis Syndrome
According to the current research on cannabinoid hyperemesis syndrome, the only way to stop CHS permanently is to stop using marijuana. Apart from that, there are some supportive treatment options an emergency department clinician or other healthcare provider may suggest during the acute phase of hyperemesis. Possible options for the treatment of cannabinoid hyperemesis syndrome include:
- Capsaicin Cream
- Frequent Hot Showers
- Intravenous Fluid For Dehydration
- Pain Medications
- Medications With Antiemetic Effects (Such as Ondansetron or Metoclopramide)
- Anti-Nausea Medications
- Proton-Pump Inhibitors
Some doctors suggest using capsaicin cream because a recent study showed that rubbing topical capsaicin cream on the abdomen decreased pain and nausea in CHS patients. It’s theorized that topical capsaicin may work to relieve nausea and pain in the same way taking a hot shower or bath does: by overriding pain and nausea sensation in the central nervous system with heat sensation.
Final Thoughts: Is CHS Real?
Marijuana is known for its ability to ease nausea, so the idea of it causing nausea can seem paradoxical. This idea seems so strange to some that they wonder whether or not cannabinoid hyperemesis syndrome is actually real. So, is cannabinoid hyperemesis syndrome real? And is it really caused by cannabinoids?
There’s some evidence that suggests the long-term heavy use of marijuana causes CHS in rare cases, but the data on CHS is very limited at this time. The current studies on CHS have also been very small and, some may argue, poorly designed. For example, one 2006 review heavily criticized the design of the defining 2004 study on CHS, calling its conclusions “unduly presumptive.” That review also pointed out that there was no blinding in the study rechallenge. A more recent 2016 review noted that follow up data on CHS was “sparse” and further stated that “evidence supporting the hypothesis of cannabinoid hyperemesis is weak.”
For now, it’s hard to say whether or not cannabinoid hyperemesis syndrome is really caused by cannabinoids. It’s possible, but we need far more evidence to understand what causes cannabinoid hyperemesis. If heavy marijuana use alone is the cause of CHS, we also need research that can help us understand how CHS could occur in some heavy cannabis users, but not in most heavy cannabis users.
With that said, if you are experiencing extreme, persistent nausea and vomiting, seek medical care no matter what you think may be causing your condition. Chronic nausea and vomiting can lead to serious health complications regardless of their cause. These symptoms may also sometimes be a sign of a more serious health condition. So, if you’re experiencing severe nausea and vomiting, take care of your health and seek the advice of a medical professional as soon as possible.