Here's Why Chronic Cannabis Use Can Cause Hyper-Vomiting

You’ve likely heard that cannabis can relieve nausea and prevent vomiting. Perhaps this is evident through personal experience. After all, Dronabinol is a synthetic version of D9-THC that is approved for the treatment of nausea and vomiting in patients undergoing chemotherapy. So when a chronic cannabis user is admitted to the emergency room because of repeated bouts of vomiting that last for days, weeks, or even years, it’s perplexing.

Especially for Charlfonte LeNee Queen of San Diego, who experienced these periodic episodes of violent retching for 17 years. Severe abdominal pain and a clouded mind led her to think she had cancer. Her bouts of vomiting made her lose a modeling job when her employer thought she was an alcoholic. But she wasn’t an alcoholic, nor did she have cancer. Instead, Ms. Queen suffered from Cannabinoid Hyperemesis Syndrome, which some doctors in states with legal cannabis are claiming is becoming increasingly common.  

What is cannabinoid hyperemesis syndrome?

Let’s first break down the terms. 'Cannabinoid' refers to the chemicals in cannabis, like D9-THC or cannabidiol, that cause this syndrome. 'Hyperemesis' means to vomit a lot (note: the term “emesis” means to vomit in medical-speak). And 'syndrome' indicates tat excessive vomiting defines this particular disorder.

Cannabinoid Hyperemesis Syndrome (CHS) was first described in 2004 by a group of Australian physicians who distinguished it from Cyclic Vomiting Syndrome (CVS) on the basis that chronic cannabis use preceded the repeated bouts of vomiting that defined CHS. So CHS is probably not a new syndrome but one that has recently differentiated as a separate syndrome.

Many physicians that diagnose patients with Cyclic Vomiting Syndrome still note cannabis as a possible culprit. Because of that, it’s difficult to track how common Cannabinoid Hyperemesis Syndrome is among cannabis users.

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CHS mostly occurs in young adults with a long history of cannabis use. While there’s variation in the latency before the pain and vomiting begin, one study found that the average duration of use before vomiting started was 16 years, but there are several cases where patients began the cyclic vomiting bouts after only 3 years or less. An additional common feature is that CHS sufferers smoke a lot of weed, on average consuming more than 3-5 times per day.

The hyperemetic phase, characterized by excessive vomiting, usually doesn’t last for more than 48 hours and sufferers often learn that taking a warm bath or shower can relieve symptoms. Between 50% and 90% of CHS patients display compulsive bathing behavior as a way to relieve abdominal pain and nausea.  

How does CHS develop?

It’s a paradox that an anti-nausea/vomit-suppressing drug like cannabis can cause vomiting. While scientists are not entirely clear how or why CHS develops, there are currently three leading hypothesis (and it could be a combination of them) that may explain this paradoxical syndrome.

Hypothesis 1: Over time, THC’s effect on type I cannabinoid receptors (CB1) in the brain is weakened, while its impact on CB1 receptors in the intestines is unaffected.

When you consume cannabis — whether through joints, vapes or edibles — THC enters the bloodstream and activates CB1 receptors wherever they’re present in the body. Two relevant regions are the intestines and the brain. By acting on CB1 receptors in the intestines, THC reduces the stomach’s ability to empty its contents into the small intestine. On its own, this actually has a pro-vomiting effect.

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But THC also activates CB1 receptors in the brain, which have a strong anti-nausea and anti-vomiting effect. THC’s actions in the brain override its actions in the intestines, leading cannabis to have well-recognized anti-emetic abilities.

Despite repeated cannabis consumption over many days, months, and years, CB1 receptors in the intestines remain remarkably resilient to repeated activation by THC. However, THC’s power to activate CB1 receptors in the brain is greatly reduced, and in some cases, has the opposite effect: blocking CB1 receptors in the brain from functioning. The consequence is that THC has a pro-vomiting effect by continuing to activate CB1 receptors in the gut, but has lost its anti-emetic effect in the brain. Vomiting results.

Support for this hypothesis comes from the fact that patients soon recover after 1-2 weeks when they stop using cannabis.

Hypothesis 2: There’s a shift in the impact of additional phytocannabinoids such as cannabidiol (CBD) and cannabigerol (CBH).

THC isn’t the only cannabinoid that gets into your bloodstream when you consume cannabis. There's a host of additional cannabinoids that can act on targets throughout the brain and body.

Two prominent cannabinoids are CBD and CBG, which vary in potency from strain to strain. While low doses of CBD are thought to be anti-emetic, high doses are thought to induce vomiting. CBG is also thought to have pro-emetic effects and could block the anti-emetic effects of THC and low-dose CBD.

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Support for this hypothesis comes from the relief of symptoms that some patients achieve by switching cannabis strains.

Hypothesis 3: The buildup of pesticides and molds on the cannabis flowers have toxic effects that cause pain and vomiting.

Regulating pesticides and molds in the cultivation, processing, and packaging of cannabis continues to be a challenge even in states with legal cannabis access. The buildup of these toxins in the body from many years of cannabis use may contribute to the symptoms of CHS. So the violent retching could actually be the body’s attempt to rid the toxin.

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Similar to Hypothesis 2, some support for this hypothesis comes from the success that some CHS sufferers have achieved by switching strains which may have lower levels of pesticides and molds.

Treatment Strategies

One of the defining features of Cannabinoid Hyperemesis Syndrome is that traditional anti-emetic drugs are ineffective at reducing symptoms. So what are your options if you develop CHS?

First, go seek medical attention! Repeated bouts of vomiting can be dangerous and could lead to dehydration and electrolyte imbalances. Therefore, you should seek care.

The second and most obvious step should be to stop consuming cannabis, which can be difficult for consumers to accept.

“These patients can initially be reluctant to see cannabis as contributing to their symptoms, which is justifiable, considering its reputation for treating nausea or persistent vomiting rather than causing them," says Dr. Tom Hutch, a Seattle-based physician who observed several cases of CHS in the emergency department last November. "[T]his is a tough strategy to sell to someone who’s not open to the possibility of chronic substance use as the cause of their problem.”

Many CHS sufferers self-soothe with frequent hot baths or showers. This remedy can effectively relieve symptoms in the short-term because heating the body activates heat-sensitive receptors in the brain called TRPV1 receptors. Activating these receptors is thought to have an anti-emetic effect by depleting a specialized group of brain chemicals, called neurotransmitters, that are involved in inducing nausea and vomiting.

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Recent case studies have revealed that capsaicin cream can also be an effective treatment for CHS. Capsaicin is the chemical in spicy foods that gives them their “heat” by activating TRPV1 receptors (normally, TRPV1 receptors are activated by hot temperatures but capsaicin lowers the temperature at which they’re active by tricking your brain into thinking your mouth is on fire).

Capsaicin cream relieves symptoms in a similar manner as a hot bath by activating TRPV1 receptors and reducing the power of the brain’s emetic response. Therefore, it could be a valuable strategy to reduce CHS symptoms during the initial period of cannabis abstinence in recovery.

A Healthy Dose of Skepticism

We still don't know how prevalent CHS is, but a paper published this week claimed that nearly 33% of heavy cannabis users (defined as using more than 20 times a month) reported experiencing symptoms of CHS in the last 6 months.

This prevalence is alarming, but there are several caveats to their report. First, data were collected from a survey of emergency room patients in a New York City hospital and therefore may represent a biased sample of patients who have additional underlying health issues that could exacerbate the negative effects of cannabis.

Additionally, a patient's sole criterion for being diagnosed with CHS was that their nausea and vomiting were relieved by a hot shower, and therefore included individuals whose symptoms may have abated despite continuing to use cannabis. They also didn't exclude people who found relief from anti-emetic drugs, which would preclude a CHS diagnosis.

Combined, these issues could artificially increase the perceived prevalence of CHS. But despite these shortcomings, this study does raise an important red flag that CHS is likely more common than people think and should be aware of the symptoms.

The Future of CHS 

CHS is an emerging condition that remains largely off the radar of scientists and physicians. As access to cannabis continues to increase, we’ll likely see an increase in the number of CHS cases. But that should also trigger more research into understanding and treating the syndrome, which will be easier when the de-stigmatization of cannabis use makes patients less likely to seek medical care.

So don't feel embarrassed about going to the hospital with a case of cannabis-induced vomiting. Your condition could help break stigmas and lead toward a cure.

Josh Kaplan, Ph.D. is a neuroscientist at the University of Washington and freelance science writer specializing in the science of cannabis. Visit neurokaplan.com to learn more. 

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