What Is Cannabis Hyperemesis Syndrome

Cannabis hyperemesis syndrome was first documented in 2004 by Allen and colleagues in South Australia, though it remained relatively obscure for nearly a decade afterward. That has changed. U.S. emergency department data show CHS prevalence rose from 4.4 per 100,000 visits in 2016 to 33.1 per 100,000 by mid-2020, with rates staying elevated through 2022. Among patients reporting chronic marijuana use of 20 or more days monthly, one study found 32.9% met CHS criteria — far from the "rare" label the condition once carried.

The syndrome presents a paradox: cannabinoids are known antiemetics, yet in certain long-term users, they produce the opposite effect. What follows covers the clinical definition, pathophysiology, symptom phases, diagnosis, and treatment.

Key Takeaways

• CHS affects roughly 1 in 3 heavy cannabis users. Among daily users presenting to emergency departments, 32.9% meet diagnostic criteria.
• Most patients wait years for a correct diagnosis. Average time from symptom onset to diagnosis: 3–6 years, often after repeated ED visits and invasive testing.
• Hot showers help—but don't confirm the diagnosis. 50% of cyclic vomiting syndrome patients without cannabis use report the same relief.
• Standard anti-nausea medications fail. Ondansetron works in under 2% of cases. Haloperidol reduces symptoms twice as effectively.
• Cannabis cessation is the only cure. No medication prevents episodes. Symptoms resolve within weeks of quitting; no permanent damage remains.
• Relapse means recurrence. Patients who resume cannabis, even years later, experience symptom return in nearly every documented case.

CHS — Clinical Definition and Diagnostic Classification

Cannabis hyperemesis syndrome is a condition of recurrent nausea, vomiting, and abdominal pain caused by prolonged cannabis use. Symptoms resolve completely when use stops and return if it resumes.

The Rome IV criteria formalized CHS as a functional gastrointestinal disorder, requiring three elements: episodic vomiting resembling cyclic vomiting syndrome, onset after prolonged cannabis consumption, and resolution following sustained abstinence.

Typical patient profile — based on the Mayo Clinic's 98-patient case series (Simonetto et al., 2012):

• Age at symptom onset: 25.3 years (mean); all patients under 50
• Cannabis use frequency: 95% used more than once weekly
• Duration before symptoms appeared: 68% had used cannabis for 2+ years
• Sex distribution: 67% male

One behavioral marker appears frequently: compulsive hot water bathing during episodes. Patients report spending hours in showers or baths, sometimes to the point of injury. However, this behavior also occurs in roughly 50% of cyclic vomiting syndrome patients who do not use cannabis, making it suggestive but not definitive.

CHS vs. cyclic vomiting syndrome: Both conditions share episodic vomiting patterns. The differentiator is straightforward — CHS resolves with cannabis cessation; CVS does not. When a patient stops using cannabis and symptoms disappear within days to weeks, CHS is confirmed. When symptoms persist despite abstinence, the diagnosis shifts to CVS.

Pathophysiology: Why Cannabis Triggers Paradoxical Vomiting

Chronic cannabis use causes vomiting by desensitizing the same receptors that make THC an effective antiemetic in the short term. The shift from antiemetic to pro-emetic effect appears to result from CB1 receptor downregulation in the central nervous system combined with continued activation of peripheral CB1 receptors in the gut.

The biphasic effect:

	Short-term cannabis use	Chronic marijuana use
CB1 receptor state	Activated normally	Downregulated/desensitized
Central effect	Inhibits emetic neurotransmitters in brainstem	Reduced antiemetic signaling
Gut effect	Slowed gastric motility	Pro-emetic gut receptors dominate
Net result	Nausea relief	Vomiting, nausea, abdominal cramping

THC is highly lipophilic and accumulates in adipose tissue over months of regular use. During stress or fasting, lipolysis releases stored THC back into circulation, potentially re-triggering symptoms even without recent consumption.

Why hot water provides relief:

The compulsive bathing behavior points to the transient receptor potential vanilloid 1 (TRPV1) channel. TRPV1 responds to heat above 43°C, capsaicin, and certain cannabinoids. Chronic cannabis exposure desensitizes TRPV1 alongside CB1. Hot water temporarily restores TRPV1 signaling; topical capsaicin cream works through the same mechanism.

Not everyone who uses cannabis heavily develops CHS. Genetic variations in cannabinoid-metabolizing enzymes and TRPV1 receptor genes may explain individual susceptibility, though this research remains early-stage.

Clinical Presentation Across Three Phases

CHS follows a predictable progression through three phases explained below.

Prodromal Phase

Duration: Weeks to years

The earliest signs are subtle: morning-predominant nausea, vague abdominal discomfort, and sometimes a fear of vomiting without actual emesis. Patients typically maintain normal eating patterns during this phase.

A counterproductive pattern often emerges: patients increase cannabis use, believing it will relieve their nausea. This escalation accelerates progression to the hyperemetic phase. Compulsive bathing behavior is rare at this stage.

Hyperemetic Phase

Duration: 24–48 hours per episode; episodes recur every few weeks to months

This is the crisis point. Symptoms include:

• Profuse vomiting — up to five times per hour during peak episodes
• Severe abdominal cramping — diffuse, colicky pain often centered around the umbilicus
• Compulsive hot water bathing — patients may shower for hours; some report scalding themselves attempting to find relief
• Dehydration and weight loss — oral intake becomes nearly impossible
• Retching — persistent dry heaving even when the stomach is empty

Standard antiemetics (ondansetron, metoclopramide, promethazine) typically fail. Emergency department visits are common; patients often undergo repeated imaging and lab workups before CHS is considered.

Recovery Phase

Duration: Days to weeks following cannabis cessation

Symptoms begin improving within 24–48 hours of stopping cannabis. Full resolution may take 7–10 days, though some patients report lingering symptoms for up to three months.

During recovery:

• Appetite returns
• Bathing behavior normalizes
• Weight stabilizes

The critical variable: sustained abstinence. Patients who resume cannabis use, even occasionally, experience near-certain symptom recurrence. This relapse pattern often confirms the diagnosis retrospectively.

Diagnostic Approach and Criteria

No blood test, imaging study, or biomarker confirms CHS. Diagnosis is clinical, and it’s based on history, symptom pattern, and response to cannabis cessation.

Rome IV diagnostic criteria require all three:

1. Episodic vomiting resembling cyclic vomiting syndrome
2. Onset after prolonged, heavy cannabis use
3. Relief following sustained cannabis abstinence

Criteria must be present for at least three months, with symptom onset at least six months before diagnosis.

The diagnostic challenge

Average time from symptom onset to diagnosis: 3–6 years. This delay stems from multiple factors:

Barrier	Consequence
Patients underreport cannabis use	Clinicians miss the connection
Cannabis is perceived as antiemetic	CHS seems paradoxical; not considered
Symptoms mimic other conditions	Extensive workups for CVS, gastroparesis, pancreatitis
Hot bathing relief isn't pathognomonic	50% of CVS patients also report it
Standard antiemetics fail	Ondansetron, metoclopramide provide little relief

Patients frequently undergo endoscopy, CT imaging, and metabolic panels before CHS enters the differential. Some are misdiagnosed with hyperemesis gravidarum during pregnancy, only to have symptoms persist postpartum.

What confirms the diagnosis

Ultimately, CHS is confirmed retrospectively: symptoms resolve after cannabis cessation and return upon re-exposure. A thorough substance use history, including frequency, duration, product type, and potency, remains the single most useful diagnostic tool. Clinicians who ask directly about cannabis use in patients with unexplained cyclic vomiting can shorten the years-long path to diagnosis.

Evidence-Based Treatment Protocols

Cannabis cessation is the only definitive treatment for CHS. All other interventions, which are medications, hot showers, topical agents, provide temporary symptom relief but do not prevent recurrence. Until the patient stops using cannabis, episodes will continue.

Acute Symptom Management

Emergency treatment targets hydration, electrolyte correction, and symptom control. The approach differs from standard nausea protocols because traditional antiemetics largely fail.

Medication	Reported Efficacy	Notes
Ondansetron	~2%	First-line in most EDs; frequently ineffective
Metoclopramide	~4%	Minimal benefit in case reports
Haloperidol	Superior to ondansetron	Twice the nausea/pain reduction in RCT; 0.05 mg/kg IV recommended
Benzodiazepines	Frequently effective	Lorazepam addresses anxiety component; addiction risk
Topical capsaicin	Adjunctive benefit	0.025% cream to periumbilical area; activates TRPV1

The HaVOC trial (2021) remains the only randomized controlled study directly comparing CHS treatments. Haloperidol reduced nausea scores by 5.0 points versus 2.4 for ondansetron, cut rescue medication use from 76% to 31%, and shortened ED stays from 5.6 to 3.1 hours.

Why Hot Showers Work

Hot water (>43°C) activates cutaneous TRPV1 receptors, redirecting blood flow to the skin and away from visceral circulation. This provides temporary relief—but patients may shower for hours, risking burns and compulsive behavior. In clinical settings, hydrothermotherapy should be limited to water temperatures below 100°F (38°C).

Long-Term Management

No FDA-approved pharmacotherapy prevents CHS episodes. Some clinicians prescribe tricyclic antidepressants (amitriptyline) off-label, extrapolating from cyclic vomiting syndrome protocols, but evidence specific to CHS is lacking.

The critical intervention is cannabis withdrawal counseling. Symptoms of cannabis withdrawal (irritability, sleep disturbance, decreased appetite) peak within 2–6 days and resolve within 2–3 weeks for most patients. These withdrawal effects are mild compared to opioid or alcohol cessation and do not require medical supervision in uncomplicated cases.

Patients who achieve sustained abstinence experience complete resolution. Those who resume use face a near-certain recurrence.

Prevention and Risk Mitigation

CHS cannot be prevented except by avoiding chronic marijuana use entirely. No dose, product type, or consumption method has been proven safe for susceptible individuals.

High-risk profile:

• Daily or weekly use for multiple years
• Early age of initiation (adolescence)
• Escalating intake over time
• Use of high-potency concentrates or synthetic cannabinoids

For those unwilling to quit, harm reduction remains unproven. Reducing frequency or switching to lower-THC products may theoretically decrease cumulative exposure, but clinical evidence does not support partial reduction as protective. Once CHS has developed, even intermittent use typically triggers recurrence.

Public health measures—mandatory labeling of high-potency products, educational campaigns targeting heavy users—may improve early recognition but cannot eliminate the syndrome in genetically susceptible populations.

Prognosis and Long-Term Outcomes

CHS is fully reversible with sustained cannabis abstinence. Symptoms typically resolve within two weeks to three months after cessation, though THC's lipophilic storage in adipose tissue can extend this timeline in heavy users.

The challenge is maintaining abstinence. A 2018 systematic review found only 54% of outpatients remained cannabis-free for two or more weeks. Of those who achieved short-term abstinence, 71% relapsed within six months, and over 70% of relapsers returned to their previous consumption levels. Each relapse typically triggers symptom recurrence. These statistics underscore why structured support matters—our team at the Canadian Centre for Addictions provides evidence-based programs that address both the physical dependency and behavioral patterns driving continued use.

Untreated or undertreated CHS carries real risks. Severe dehydration can cause acute kidney injury and electrolyte imbalances. In 2016, the first documented fatalities from CHS-related hyponatremic dehydration were reported. Repeated vomiting also risks esophageal injury and aspiration pneumonia.

For patients who achieve lasting cessation, prognosis is excellent. Unlike cyclic vomiting syndrome, CHS does not persist once the offending agent is removed. The condition leaves no known permanent gastrointestinal damage.

The Paradox That Points to the Exit

CHS represents one of medicine's clearer cause-and-effect relationships: remove cannabis, and the syndrome resolves. Yet that simplicity masks real difficulty—years of habitual use, withdrawal discomfort, and the counterintuitive reality that a drug known for suppressing nausea is causing it. Recognition is the first step; sustained abstinence, often with professional support, is the only path to lasting relief.

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