The Most Comprehensive Systematic Review of CHS: 183 Studies, 14 Diagnostic Features, and Treatment Options | Research

The takeaway

A systematic review of 183 studies identified 14 diagnostic characteristics of CHS, confirmed that cannabis cessation is the only definitive treatment, and found that hot bathing provided relief in virtually all reported cases.

Anyone experiencing cyclical vomiting who uses cannabis regularly.

100% had regular cannabis use, 96.8% resolved with cessation, 92.3% relieved by hot baths

The Backstory

The emergency department physician has seen this before. A young man, mid-twenties, doubled over the toilet in triage. He has been vomiting for twelve hours straight. His skin is flushed and dehydrated. He is begging — not for medication, not for fluids — for a hot shower. The hotter the better. Scalding, if possible.

The standard anti-nausea medications have already failed. Ondansetron did nothing. Promethazine did nothing. He has been to the ER three times in the past four months with the same presentation. Each time, tens of thousands of dollars in workup — CT scans, endoscopies, blood panels — found nothing wrong. One doctor suggested it was anxiety. Another suspected cyclic vomiting syndrome. Nobody asked the right question until now.

"How much cannabis do you use?"

"Every day. Multiple times a day. For about six years."

The diagnosis writes itself. But it is also one of the cruelest ironies in all of pharmacology: the most effective anti-nausea substance known to medicine is causing uncontrollable vomiting.

The Systematic Review

Cecilia Sorensen and colleagues — an interdisciplinary team spanning emergency medicine, pharmacy, psychology, and toxicology at the University of Colorado and Denver Health — conducted the most comprehensive systematic review of cannabinoid hyperemesis syndrome (CHS) to date.

Study Design

The Definitive Systematic Review of CHS

2,178

Articles screened

from MEDLINE, Embase, Web of Science, and Cochrane

183

Studies included

in cumulative synthesis after screening

Diagnostic features

identified across the literature

GRADE

Evidence framework

used to evaluate pathophysiology and treatment claims

Sorensen et al. (2017), J Med Toxicol 13(1):71-87

The review searched five major databases from January 2000 through September 2015, screened 2,178 articles, removed duplicates to review 1,253 abstracts, and ultimately included 183 studies. The majority were case reports and case series — the nature of a syndrome that had only been formally named thirteen years earlier.

The Diagnostic Profile

The cumulative synthesis produced the clearest clinical picture of CHS available anywhere in the medical literature.

Diagnostic Criteria

The 14 Features of Cannabinoid Hyperemesis Syndrome

Regular cannabis use

Present in 100% of cases — any duration, but at least weekly (97.4% used weekly or more)

Cyclic nausea and vomiting

Present in 100% — episodic, not constant, often with predictable periodicity

Resolution with cessation

96.8% of patients saw complete resolution after stopping cannabis

Compulsive hot bathing

92.3% reported relief from hot showers or baths — the most distinctive and recognizable feature

Abdominal pain

85.1% — often severe, epigastric or periumbilical, driving expensive diagnostic workups

Male predominance

72.9% of reported cases were male — likely reflecting higher rates of heavy daily use

Sorensen et al. (2017), J Med Toxicol

The diagnostic pattern is striking in its consistency. CHS is not a vague, subjective diagnosis. It is a syndrome with a nearly pathognomonic feature — compulsive hot bathing — that no other common cause of cyclic vomiting produces. Emergency physicians who know to ask about cannabis use and hot shower behavior can make the diagnosis at the bedside in minutes, potentially saving thousands of dollars in unnecessary testing.

The Three Phases

The review confirmed that CHS follows a characteristic three-phase pattern first described in the early case literature:

Process

The Clinical Course of CHS

Study methodology

The Paradox: Why Does Cannabis Cause Vomiting?

This is the question that makes CHS so scientifically fascinating. Cannabis is among the most effective anti-emetics known — it has been used for chemotherapy-induced nausea since the 1970s and is FDA-approved for this purpose (as dronabinol and nabilone). How can the same substance that prevents vomiting also cause uncontrollable vomiting?

Biological Mechanism

The Paradox of Cannabinoid Hyperemesis

▼

Proposed mechanism

The Sorensen review was candid about the limits of understanding: the pathophysiology section concluded that the mechanisms remain "unclear" with a "dearth of research dedicated to investigating its underlying mechanism." This honesty is important — CHS is a clinical reality whose biological explanation is still being worked out.

The Treatment Landscape

Treatment

What Works for CHS

Cannabis cessation

The only definitive cure. Resolution in 96.8% of cases. Reducing use does not work — complete abstinence is required.

Hot water

Temporary relief during acute episodes via TRPV1 activation. Not a treatment — a coping mechanism that can cause burns and dehydration.

Topical capsaicin

Applied to the abdomen, provides relief through the same TRPV1 mechanism as hot water. Emerging as a first-line acute treatment in EDs.

Haloperidol

Dopamine antagonist that has shown promise where standard anti-emetics fail. Small studies and case reports support its use.

Standard anti-emetics

Ondansetron (Zofran), promethazine, and metoclopramide are frequently INEFFECTIVE for CHS — a key diagnostic clue.

IV fluids

Supportive care for dehydration. Essential but does not address the underlying syndrome.

Sorensen et al. (2017), J Med Toxicol

The failure of standard anti-emetics is itself a diagnostic feature. When a chronic cannabis user presents with cyclic vomiting that does not respond to ondansetron but improves dramatically with hot water, the diagnosis is almost certainly CHS. This pattern distinguishes it from cyclic vomiting syndrome and virtually all other causes of recurrent vomiting.

From Obscure Case Report to Emergency Department Epidemic

When J.H. Allen first described the syndrome in 2004 — a case series of 19 patients in South Australia, 9 of whom met criteria for the full syndrome — it was a medical curiosity. Most physicians had never heard of it. Many did not believe it was real.

Research Timeline

The Rise of CHS Recognition

2004

2009-2012

2017

2018-2022

2024

Historical research record

The numbers are stark. CHS-related emergency department visits in the United States increased roughly seven-fold between 2016 and 2020. In states with legalized recreational cannabis, rates were more than double those in non-legalized states. The increasing potency of modern cannabis products — concentrates, vapes, edibles with precise high doses — appears to be a key driver. CHS is no longer rare. It is a routine part of emergency medicine practice in any state with legal cannabis.

What People Get Wrong

Myth vs. Reality

✕Myth

CHS only affects people who smoke enormous amounts of cannabis

✓Reality

While heavy daily use is the typical pattern, the Sorensen review found that 'regular cannabis for any duration of time' was present in 100% of cases, and the specific threshold for developing CHS is unknown. Some patients develop CHS after relatively modest use — the susceptibility appears to involve individual genetic and metabolic factors, not just quantity consumed.

The Evidence

Sorensen et al. (2017); Russo (2022) genomic investigation

The most dangerous misconception about CHS is the belief that it cannot happen to you. Many patients with CHS initially refuse to accept the diagnosis because they have used cannabis for years without problems. The prodromal phase — increased nausea treated with more cannabis — can last months or years before the full hyperemetic crisis hits. During this phase, patients are often told by fellow cannabis users (and sometimes by uninformed healthcare providers) that cannabis should help their nausea, creating a vicious cycle of increasing use and worsening symptoms.

The Bigger Picture

CHS matters far beyond the emergency department. It is a natural experiment in what happens when the endocannabinoid system is chronically overstimulated — a living demonstration of receptor desensitization, dose-response reversal, and the difference between acute pharmacology and chronic adaptation.

For the broader cannabis conversation, CHS serves as a corrective to the notion that cannabis is entirely benign. It is not. At high doses over extended periods, it can produce a syndrome so severe that patients end up in the emergency department repeatedly, undergo unnecessary surgeries, lose weight dangerously, and in rare documented cases, die from complications including dehydration-related kidney failure and cardiac events.

But CHS is also treatable — with the simplest intervention imaginable: stop using cannabis. The recovery rate approaches 97%. For a syndrome that can be utterly debilitating, the cure is complete and available to everyone.

How do I know if I have CHS versus regular food poisoning or a stomach bug?

The key distinguishing features: CHS is cyclical (it comes back), it occurs exclusively in regular cannabis users, standard anti-nausea medications do not work, and hot showers or baths provide dramatic temporary relief. If you use cannabis regularly and have had multiple episodes of severe vomiting that seem to defy diagnosis, CHS should be strongly considered. Our full CHS guide walks through the diagnosis step by step.

Can I keep using cannabis if I reduce my intake?

The evidence from this systematic review is clear: reducing cannabis use does not resolve CHS. Complete cessation was required in essentially all successfully treated cases. Even patients who reduced to occasional use frequently relapsed into the hyperemetic cycle. The syndrome resolves only with full abstinence.

Why do hot showers help?

The leading theory involves the TRPV1 receptor — the same receptor activated by capsaicin (chili pepper heat). TRPV1 is coexpressed with CB1 cannabinoid receptors in the gut. Hot water activates TRPV1 in a way that may temporarily restore the balance disrupted by chronic CB1 desensitization. This is also why topical capsaicin cream applied to the abdomen can provide similar relief.

How common is CHS?

More common than previously thought and increasing. One study found that approximately 32.9% of daily or near-daily cannabis smokers in an urban ED met criteria for CHS. Emergency department visits for CHS increased roughly seven-fold in the US between 2016 and 2020. As cannabis potency and availability increase, CHS rates are expected to continue rising.

Cannabinoid Hyperemesis Syndrome: Diagnosis, Pathophysiology, and Treatment — a Systematic Review

Sorensen CJ, DeSanto K, Borgelt L, Phillips KT, Monte AA (2017) · Journal of Medical Toxicology

PubMed DOI

Related Research

Key studies in this area

Cannabinoid Hyperemesis: The First Description

Allen et al. (2004)

Cannabinoid Hyperemesis: A Case Series of 98 Patients

Simonetto et al. (2012)

Cannabinoid Hyperemesis Syndrome Survey and Genomic Investigation

Russo et al. (2022)

CHS Emergency Department Visits After Cannabis Legalization in Ontario

Myran et al. (2022)

What the researchers found

This extensive systematic review analyzed 2,178 articles, ultimately including 183 studies with cumulative case data. The diagnostic profile of CHS was characterized by 14 features, with the major ones being:

100% had a history of regular cannabis use. 100% had cyclic nausea and vomiting. 96.8% had resolution of symptoms after stopping cannabis. 92.3% reported compulsive hot bathing with symptom relief. 97.4% used cannabis at least weekly. 85.1% had abdominal pain. 72.9% were male.

The pathophysiology remained unclear despite extensive review, with no single mechanism adequately explaining why only some chronic users develop CHS. For treatment, the evidence was strongest for cannabis cessation as the definitive cure. In the acute setting, supportive care with IV fluids, dopamine antagonists (like haloperidol), topical capsaicin cream, and avoidance of narcotic medications showed some benefit. Standard antiemetics were frequently ineffective.

Why it matters

This is the most comprehensive systematic review of CHS published to date, providing clinicians with the best available evidence for diagnosis and treatment. The high specificity of the diagnostic criteria (particularly the hot bathing behavior at 92.3%) gives clinicians a clear clinical picture to recognize.

The numbers in context

2,178 articles screened. 183 included. 14 diagnostic characteristics identified. Regular cannabis use: 100%. Cyclic vomiting: 100%. Resolution with cessation: 96.8%. Hot bathing relief: 92.3%. Weekly+ use: 97.4%. Abdominal pain: 85.1%. Male predominance: 72.9%.

How the study worked

Systematic review searching MEDLINE, Ovid MEDLINE, Embase, Web of Science, and the Cochrane Library from 2000 to September 2015. Articles were evaluated using GRADE criteria. Data from case reports and series were combined in a cumulative synthesis.

What this study cannot tell us

Most included studies were case reports and case series (low-quality evidence by GRADE standards). Publication bias likely favors reporting of classic CHS presentations, potentially inflating the frequency of diagnostic features. The search ended in 2015, and CHS knowledge has continued to evolve. No randomized treatment trials existed at the time of review.

How to read the evidence

Strong evidence from a comprehensive systematic review, though underlying studies are mostly case-level evidence.

When this study was published

Published in 2017. Landmark systematic review providing the diagnostic framework for CHS.

The bigger picture

CHS has evolved from an obscure case report curiosity to a well-characterized clinical entity. This systematic review provided the diagnostic framework that clinicians needed to confidently identify and manage CHS. The male predominance (72.9%) may reflect higher rates of heavy cannabis use among males rather than true biological susceptibility differences.

Questions still open

Why do only some chronic cannabis users develop CHS? What is the minimum duration or quantity of cannabis use that can trigger CHS? Will the increasing potency of cannabis products change CHS prevalence or presentation?

Common questions

How do I know if I have CHS?

The key features from this review: regular cannabis use (at least weekly), cyclical episodes of nausea and vomiting, abdominal pain, characteristic relief from hot baths or showers, and resolution when you stop using cannabis. If you experience these together, CHS should be strongly considered.

Is there a cure for CHS besides quitting cannabis?

Based on this comprehensive review, cannabis cessation was the only treatment that consistently resolved CHS (96.8% of cases). In the acute setting, hot baths, haloperidol, IV fluids, and topical capsaicin cream provided temporary relief. No medication permanently resolved CHS while cannabis use continued.

Read the original research

Cannabinoid Hyperemesis Syndrome: Diagnosis, Pathophysiology, and Treatment-a Systematic Review.

Journal of medical toxicology : official journal of the American College of Medical Toxicology, 13(1), 71-87

View on PubMed ↗Publisher’s paper ↗

Citation

Sorensen, Cecilia J; DeSanto, Kristen; Borgelt, Laura; Phillips, Kristina T; Monte, Andrew A. (2017). Cannabinoid Hyperemesis Syndrome: Diagnosis, Pathophysiology, and Treatment-a Systematic Review.. Journal of medical toxicology : official journal of the American College of Medical Toxicology, 13(1), 71-87. https://doi.org/10.1007/s13181-016-0595-z