When Weed Turns Deadly: Inside Cannabis Hyperemesis Syndrome and Why the World Just Gave It an Official Name
A “mysterious vomiting disorder tied to long-term marijuana use” has just been formally recognized by global health officials. That disorder is cannabis (cannabinoid) hyperemesis syndrome (CHS)—a condition that can push otherwise healthy people into repeated emergency room visits, severe dehydration, and even kidney failure. With a new World Health Organization (WHO) diagnostic code and alarming new data showing skyrocketing emergency-room cases, CHS has moved from medical curiosity to urgent public-health warning.
What Exactly Is Cannabis Hyperemesis Syndrome?
Cannabis hyperemesis syndrome is characterized by:
Recurrent waves of severe nausea
Intense, often uncontrollable vomiting
Cramping abdominal pain
A striking behavior: patients often stand in very hot showers or baths for relief
It almost always appears in people who use cannabis frequently (often daily) and for months to years, especially with high-potency products.
Clinically, CHS is tricky because it mimics many other conditions—food poisoning, stomach flu, gallbladder disease, even surgical emergencies. Patients often undergo battery after battery of tests before someone connects the dots between their vomiting and their cannabis use.
The underlying mechanism is still not fully understood, but leading theories include:
Overstimulation or dysregulation of the endocannabinoid system after prolonged, heavy use
Interaction with TRPV1 (heat/pain) receptors, which may explain why hot water and capsaicin cream sometimes bring temporary relief
A paradoxical shift where cannabis, usually anti-nausea at low doses, becomes pro-emetic (vomit-triggering) at sustained high exposure
From Mystery to Official Diagnosis: WHO and the New Global Code
For years, CHS was described under vague labels such as “cyclical vomiting” or “vomiting, unspecified,” making it hard to track and easy to overlook.
That has now changed.
October 1, 2025 – The World Health Organization formally standardized “cannabis hyperemesis syndrome” in the International Classification of Diseases (ICD). In the ICD-10 family, CHS is now coded as R11.16 (Cannabis hyperemesis syndrome), listed under symptoms and abnormal findings.
In ICD-11, CHS appears as a synonym under DD90.4 – Functional nausea or vomiting, meaning it is recognized across the WHO’s most up-to-date disease framework.
In the U.S., the new ICD-10-CM code R11.16 also went into effect on October 1, 2025, giving hospitals and payers a specific label for CHS rather than forcing them to lump it into generic vomiting codes.
Why that matters:
Doctors can now formally diagnose CHS instead of coding it as a vague gastrointestinal complaint.
Health systems, researchers, and policymakers can track how often and where it occurs, which populations are most affected, and what outcomes patients experience.
Insurers and governments can better measure the financial and clinical burden of cannabis-related harms.
This shift from “mysterious syndrome” to official WHO-coded diagnosis is exactly what public-health experts said was needed to get serious about the problem.
A Quiet Explosion: How Common Is CHS Becoming?
CHS is still considered “rare but relevant” on a population level—but within certain subgroups (heavy, long-term users of high-potency cannabis), it is far from rare.
Recent data are sobering:
A large JAMA Network Open study of U.S. emergency department (ED) visits from 2016–2022 documented a sharp increase in CHS-consistent cases, especially after 2020.
Researchers found that the estimated probability that a vomiting-related ED visit was actually CHS more than tripled, peaking at about 13% in 2021 before settling around 10% in 2023—still far above pre-pandemic levels.
Media analyses of that work suggest CHS-related ER visits may have risen around 650% from 2016 through their pandemic peak, with the steepest increases among 18- to 35-year-olds.
Other research and surveillance systems echo this trend:
National Geographic reported that CHS cases in the U.S. have roughly doubled in recent years, describing it as a “strange syndrome” now seen regularly in emergency departments.
A 2024 UCHealth summary called CHS the leading cause of marijuana-related ER visits at their system, largely among daily users with several years of heavy consumption.
The CDC has documented significant increases in cannabis-involved ED visits among youth, especially since legalization and during the COVID-19 pandemic, raising concerns that CHS and other cannabis-related harms are hitting adolescents and young adults hard.
A Canadian study in JAMA Network Open found that ED visits for CHS increased after recreational legalization and commercialization, underscoring that policy liberalization can have measurable downstream effects on acute cannabis-related harms.
All of this reinforces a simple reality: as cannabis use becomes more frequent, more potent, and more normalized, CHS is emerging as a serious, measurable consequence.
The Human Cost: Why This Can Be Life-Threatening
On paper, CHS is “just” vomiting. In the real world, it can be devastating.
Patients with CHS often:
Vomit dozens of times per day during flare-ups
Become severely dehydrated and electrolyte-depleted
May develop acute kidney injury or even kidney failure from repeated dehydration and rhabdomyolysis (muscle breakdown)
Miss work or school, cycle through multiple ER visits, and rack up substantial medical bills
Because early presentations look like common GI illnesses, patients frequently undergo:
CT scans, ultrasounds, endoscopies
Extensive blood work
Empiric treatments for ulcers, gallbladder disease, or infections
—all while the real culprit (chronic high-dose cannabis) goes unaddressed.
And there’s a psychological hurdle: many patients do not want to accept that cannabis—the substance they may use for relaxation, anxiety, sleep, or nausea—could be the very thing making them desperately sick.
This denial delays diagnosis, prolongs suffering, and in extreme cases can escalate to life-threatening complications.
Who Is Most at Risk?
Patterns emerging from recent research and clinical reports suggest CHS is most common among:
Daily or near-daily cannabis users
People using high-potency (high-THC) products, including concentrates, dabs, and modern flower with THC levels far above historical norms
Young adults (18–35), particularly men, though women are increasingly represented in ED data
Those who started using cannabis in adolescence and escalated to heavy, chronic use over time
Importantly, not everyone who uses cannabis heavily gets CHS. It appears to affect a susceptible subset of users—one reason some clinicians refer to it as “rare but highly consequential.”
How Is CHS Treated—and Can It Be Cured?
In the emergency department, clinicians focus on stabilizing the patient:
IV fluids and electrolyte correction
Pain management
Antiemetics (though common drugs like ondansetron often work poorly)
Several studies and case reports suggest:
Haloperidol may be significantly more effective than standard anti-nausea medications for acute CHS episodes.
Topical capsaicin cream and hot showers activate similar receptors and can meaningfully ease symptoms for some patients.
But there’s a crucial bottom line:
The only consistently effective long-term “cure” is stopping cannabis use.
Patients who completely stop using cannabis typically see their symptoms resolve and remain in remission. Those who resume heavy use frequently relapse.
Because many people use cannabis to cope with anxiety, trauma, pain, or insomnia, quitting often requires addiction-informed support, counseling, and, in some cases, treatment for underlying mental health or substance use disorders.
Why Formal Global Recognition Is a Big Deal
The new WHO recognition and ICD code might sound bureaucratic, but it changes the landscape in several critical ways:
Clinical Awareness
A named, coded syndrome pushes CHS into medical curricula, clinical guidelines, and continuing education.
Emergency physicians and primary-care providers are more likely to ask about cannabis use and to connect chronic vomiting plus hot-shower behavior with CHS.
Data and Surveillance
With a dedicated code (R11.16), hospitals and public-health agencies can track CHS trends across countries and regions.
Researchers can better study risk factors, outcomes, and effective treatments, instead of piecing together indirect signals from generic vomiting codes.
Policy and Prevention
Policymakers can no longer claim there is “no hard data” on severe cannabis-related vomiting; the code will generate that data.
Jurisdictions that have legalized cannabis—or are considering it—can incorporate CHS data into public-health messaging, product regulation, and harm-reduction strategies.
Patient Education and Safety
The new classification helps validate patients’ experiences: CHS is real, recognized by the WHO, and potentially life-threatening.
Clear naming can save lives by prompting earlier diagnosis, fewer unnecessary tests, and faster counseling on cessation.
The Bigger Picture: Cannabis, Potency, and Public Health
The formal recognition of CHS lands amid a broader debate: as cannabis is legalized, commercialized, and marketed as “natural” or “harmless,” are we underestimating its risks—especially at high doses and over years?
Emerging evidence suggests:
Legalization and commercialization have been associated with increased adult cannabis use, more frequent use, and higher rates of cannabis use disorder in some regions.
Health-care utilization for cannabis-related harms—including psychosis, accidental pediatric ingestions, and CHS—has clearly risen in both the U.S. and Canada.
CHS does not mean that every cannabis user is in danger or that all medicinal uses are invalid. But it does shatter the myth that cannabis is a risk-free, one-size-fits-all solution. For a growing number of chronic users, it can be violently toxic.
Moving Forward: What Needs to Happen Now
In light of WHO’s formal recognition and the surge in cases, several steps are urgent:
Integrate CHS into medical and nursing education so new clinicians recognize it quickly.
Embed CHS screening (asking specifically about chronic cannabis use and hot-shower behavior) into ED workflows for patients with recurrent vomiting.
Launch public-health campaigns—particularly in high-use, high-potency markets—warning that heavy, long-term cannabis use can cause severe vomiting and may require cessation.
Expand addiction and mental-health services that address cannabis-use disorder, not only opioids or alcohol.
Fund mechanistic research to understand why some users develop CHS and others do not, potentially identifying genetic or metabolic susceptibility factors.
Conclusion
The official recognition of cannabis hyperemesis syndrome by global health authorities is more than a new code in a manual. It is an acknowledgment that, in an era of potent, normalized cannabis, there is a real and rising cost for a subset of users—a cost paid in IV lines, hospital beds, missed work, and, sometimes, organ damage.
For clinicians, the message is simple: think CHS when chronic cannabis users present with relentless vomiting—especially if they live in the shower.
For policymakers and the public, it’s a warning: legalization and commercialization must be matched with honest education, careful regulation, and real support for those harmed by a drug that is far from harmless for everyone.
References
Allen, J. H., de Moore, G. M., Heddle, R., & Twartz, J. C. (2004). Cannabinoid hyperemesis: Cyclical hyperemesis in association with chronic cannabis abuse. Gut, 53(11), 1566–1570. JAMA Network
Centers for Disease Control and Prevention. (2023). Cannabis-involved emergency department visits among persons aged <25 years — United States, 2019–2022. MMWR Weekly, 72(28), 761–768. CDC
Find-A-Code / WHO. (2025). R11.16 – Cannabis hyperemesis syndrome (ICD-10 and ICD-10-CM). AAPC Alpha Coding Experts
Loganathan, P., Gajendran, M., & Goyal, H. (2024). A comprehensive review and update on cannabis hyperemesis syndrome. Pharmaceuticals, 17(11), 1549. ResearchGate
Myran, D. T., Roberts, R., Pugliese, M., Taljaard, M., Tanuseputro, P., & Pacula, R. L. (2022). Changes in emergency department visits for cannabis hyperemesis syndrome following recreational cannabis legalization and commercialization in Ontario, Canada. JAMA Network Open, 5(9), e2231937. JAMA Network
National Geographic. (2024, November 11). This strange syndrome is linked to regular cannabis use—and cases have doubled. National Geographic
Ruberto, A. J., Sivilotti, M. L. A., Forrester, S., Hall, A. K., Crawford, F. M., & Day, A. G. (2021). Intravenous haloperidol versus ondansetron for cannabis hyperemesis syndrome (HaVOC): A randomized, controlled trial. Annals of Emergency Medicine, 77(6), 613–619. JAMA Network
Ruffle, J. K., Bajgoric, S., Samra, K., Chandrapalan, S., Aziz, Q., & Farmer, A. D. (2015). Cannabinoid hyperemesis syndrome: An important differential diagnosis of persistent unexplained vomiting. European Journal of Gastroenterology & Hepatology, 27(12), 1403–1408. JAMA Network
Swartz, J. A., & Franceschini, D. (2025). Cannabinoid hyperemesis syndrome, 2016 to 2022. JAMA Network Open, 8(11), e2545310. https://doi.org/10.1001/jamanetworkopen.2025.45310 JAMA Network
UCHealth. (2024, October 26). What is CHS? The leading cause of marijuana-related ER visits. UCHealth
World Health Organization / ICD-11 MMS. (2025). DD90.4 – Functional nausea or vomiting (includes cannabinoid hyperemesis syndrome). FindACode
(Additional news coverage summarizing the WHO coding decision and the 650% increase in CHS-related ED visits: Fox News Digital; University of Washington School of Medicine news releases; Axios; ScienceDaily.) Addictions, Drug & Alcohol Institute KOMO Fox News
