Introduction

Cannabinoid Hyperemesis Syndrome (CHS) is a condition characterized by recurrent, stereotypical episodes of severe nausea and vomiting that develop in the setting of prolonged, heavy cannabis use and resolve with sustained abstinence from cannabis. First described in the medical literature in 2004 by Allen and colleagues in a case series from South Australia, CHS has rapidly emerged as one of the most common identifiable causes of recurrent vomiting in emergency departments, particularly in regions where cannabis use is prevalent or legalized.

Despite the seeming paradox of cannabis, which is widely recognized for its antiemetic properties, causing severe vomiting, the clinical entity is now well established. The Rome IV classification, published in 2016, formally incorporated CHS into its framework for functional gastroduodenal disorders as category B3c within the nausea and vomiting disorders, alongside chronic nausea vomiting syndrome (B3a) and cyclical vomiting syndrome (B3b). This formalization provided the first consensus-based diagnostic criteria for CHS, giving clinicians a structured framework for identifying the condition and distinguishing it from other causes of recurrent vomiting.

The clinical importance of recognizing CHS cannot be overstated. Patients with undiagnosed CHS frequently undergo extensive, costly, and invasive diagnostic workups (repeated CT scans, endoscopies, gastric emptying studies, exploratory surgeries) before the diagnosis is made. The average time from symptom onset to diagnosis has been reported as 3 to 7 years in multiple case series, during which patients accumulate significant healthcare costs, miss work, and suffer substantial impairment in quality of life. Prompt recognition using the Rome IV criteria can dramatically shorten this diagnostic odyssey.

Classification Within the Rome IV Framework

CHS is classified under Rome IV Category B: Gastroduodenal Disorders, within the B3 subcategory of nausea and vomiting disorders:

Code	Disorder	Key Distinguishing Feature
B3a	Chronic Nausea Vomiting Syndrome	Chronic nausea and/or vomiting without a cyclical pattern; not episode-based
B3b	Cyclical Vomiting Syndrome (CVS)	Stereotypical episodes of intense vomiting separated by symptom-free intervals; no cannabis causation
B3c	Cannabinoid Hyperemesis Syndrome (CHS)	CVS-like pattern occurring in the context of prolonged cannabis use; resolves with cannabis cessation

The placement of CHS alongside CVS is deliberate and clinically significant. CHS and CVS share a nearly identical clinical phenotype during active episodes (severe nausea, protracted vomiting, stereotypical pattern, prodromal phase, emetic phase, recovery phase). The distinguishing factor is the etiological relationship to cannabis: CHS is caused by cannabis, while CVS occurs independently of cannabis use. This distinction has direct therapeutic implications, as the definitive treatment for CHS is cannabis cessation, whereas CVS management centers on prophylactic and abortive pharmacotherapy.

The Rome IV Diagnostic Criteria for CHS

The diagnosis of CHS under Rome IV requires that all of the following criteria be met:

1. Stereotypical episodic vomiting resembling cyclical vomiting syndrome (CVS) in onset and duration
2. Presentation after prolonged, excessive cannabis use
3. Relief of vomiting episodes after sustained cessation of cannabis use

Temporal Requirements

The diagnostic criteria must be fulfilled for the last 3 months, with symptom onset at least 6 months prior to diagnosis. This temporal gate ensures that the diagnosis captures a chronic, established pattern rather than an isolated or self-limited episode of cannabis-associated vomiting.

Supportive Criterion

Rome IV identifies one supportive feature that, while not required for diagnosis, strongly supports the clinical diagnosis when present:

• Pathological bathing behavior: The patient engages in compulsive, prolonged hot baths or showers specifically to relieve nausea and vomiting symptoms.

Pathological bathing behavior is considered nearly pathognomonic for CHS when present in the appropriate clinical context. While it is not universal (estimates suggest it occurs in 70 to 90 percent of CHS patients), its presence in a patient with recurrent vomiting and cannabis use history should immediately raise suspicion for CHS.

Detailed Examination of Each Criterion

Criterion 1: Stereotypical Episodic Vomiting Resembling CVS in Onset and Duration

This criterion defines the vomiting pattern that characterizes CHS. The episodes are not random or variable; they follow a recognizable, repeating pattern that the patient can often describe in detail. The key features of the stereotypical pattern include:

Prodromal Phase

Most CHS episodes begin with a prodromal phase lasting hours to days before the onset of overt vomiting. During this phase, patients typically report:

• Escalating nausea, often described as "waves" of nausea that become progressively more intense
• Vague epigastric or periumbilical discomfort
• Anorexia and aversion to food
• Early-morning predominance (nausea and discomfort are characteristically worst in the early morning hours, often waking the patient from sleep)
• Anxiety or a sense of impending illness that the patient recognizes from prior episodes

Some patients learn to recognize their prodromal symptoms and may escalate cannabis use during this phase in an attempt to self-treat the nausea, paradoxically worsening the cycle.

Emetic (Hyperemetic) Phase

The emetic phase is the most clinically dramatic component and the phase that most commonly brings patients to medical attention. It is characterized by:

• Intense, protracted vomiting: Patients may vomit dozens of times per day, often every 15 to 30 minutes during the peak of an episode. The vomiting is typically forceful and often described as "uncontrollable."
• Intractable nausea: Nausea persists continuously between vomiting episodes and is often described by patients as the most distressing symptom.
• Abdominal pain: Diffuse or epigastric abdominal pain, often described as crampy or colicky, accompanies the vomiting in most patients.
• Retching: Dry heaving persists even after the stomach is empty.
• Duration: The emetic phase typically lasts 24 to 48 hours but can persist for up to 7 to 10 days in severe cases.
• Dehydration: Profound fluid and electrolyte losses from vomiting, poor oral intake, and often excessive bathing (hot water exposure promotes insensible losses) can produce clinically significant dehydration requiring intravenous fluid resuscitation.

Recovery Phase

Following the emetic phase, patients enter a recovery phase during which vomiting and nausea gradually subside over hours to days. Appetite returns, and the patient resumes normal eating and activity. Between episodes, patients are typically entirely asymptomatic (aside from mild residual nausea in some cases), which is a hallmark feature shared with CVS and a key distinction from chronic nausea vomiting syndrome.

Episode Frequency and Intervals

CHS episodes recur at variable intervals, ranging from weekly to monthly in most patients. The inter-episode intervals are generally shorter and more predictable than those seen in CVS. Some patients report identifiable triggers for individual episodes, including particularly heavy cannabis use sessions, alcohol consumption, fasting, physical or emotional stress, and menstruation in women.

Criterion 2: Presentation After Prolonged, Excessive Cannabis Use

This criterion establishes the necessary temporal and dose-response relationship between cannabis exposure and symptom development. Several key points require emphasis:

What Constitutes "Prolonged" Use?

CHS typically develops after years (not weeks or months) of regular cannabis use. The majority of patients in published case series report daily or near-daily cannabis use for at least 1 to 2 years before symptom onset, with many reporting use histories exceeding 5 to 10 years. The onset of CHS does not correlate with recent initiation of cannabis use; rather, it appears after a prolonged period of chronic exposure during which the endocannabinoid system has been subjected to sustained, supraphysiological stimulation.

What Constitutes "Excessive" Use?

There is no universally defined threshold for "excessive" cannabis use in the context of CHS. However, the overwhelming majority of described CHS patients report heavy use patterns, including:

• Daily use (most commonly multiple times per day)
• Use of high-potency cannabis products (concentrates, dabs, edibles with high THC content)
• Cannabis use that the patient acknowledges as exceeding casual or occasional recreational use

CHS has been described most commonly with inhaled (smoked or vaporized) cannabis but has also been reported with edible cannabis products. The relationship to specific cannabinoid profiles (THC-dominant vs. CBD-rich products) is not fully characterized, though most cases involve THC-predominant preparations.

All Routes and Forms of Cannabis

Clinicians should inquire about all forms of cannabis use, including smoked flower, vaporized concentrates (wax, shatter, dabs), edibles, tinctures, and topical preparations. Patients may not volunteer information about all routes of use, and some may not consider certain products (such as CBD oils or delta-8 THC) to be "cannabis." A comprehensive substance history is essential.

Criterion 3: Relief of Vomiting Episodes After Sustained Cessation of Cannabis Use

This criterion is both the most diagnostically powerful and the most clinically challenging to establish. Complete and sustained resolution of vomiting episodes following cannabis abstinence is the definitive confirmation of the CHS diagnosis. However, several practical challenges complicate its application:

• Achieving sustained abstinence is difficult. Cannabis use disorder is present in many CHS patients, and achieving complete abstinence may require addiction treatment support. Patients who reduce but do not eliminate cannabis use may experience partial but not complete symptom resolution, making the criterion difficult to assess.
• Adequate duration of abstinence is required. THC is highly lipophilic and can be stored in adipose tissue for weeks. Clinical resolution of CHS typically requires 1 to 3 months of complete abstinence before the emetic episodes cease, though some patients report improvement within 1 to 2 weeks. A trial of at least 2 to 4 weeks of verified abstinence is generally recommended before concluding that cessation did not help.
• Relapse confirms the diagnosis. Patients who achieve remission with abstinence and then resume cannabis use frequently experience return of the vomiting episodes, often within days to weeks. This relapse pattern, while distressing for the patient, provides strong confirmatory evidence for CHS.
• Prospective vs. retrospective assessment. In some patients presenting for the first time, the diagnosis must be made prospectively by recommending cannabis cessation and observing for symptom resolution. In other patients, a history of prior episodes that resolved during periods of abstinence can retrospectively satisfy this criterion.

Temporal Requirements

The Rome IV temporal requirements (criteria fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis) ensure that the diagnosis captures a chronic, recurrent pattern. A single episode of vomiting in a cannabis user, even if severe, does not meet Rome IV criteria for CHS. The temporal gate also allows time for the characteristic stereotypical pattern to become apparent and for alternative diagnoses to be considered and excluded.

Pathological Bathing Behavior: The Signature Feature

Although classified as a supportive rather than required criterion, pathological bathing behavior is one of the most recognizable and clinically distinctive features of CHS. It is present in approximately 70 to 90 percent of patients in published case series and is rarely seen in other causes of recurrent vomiting, making it nearly pathognomonic for CHS when present in the appropriate clinical context.

Characteristics of Pathological Bathing

• Compulsive hot water immersion: Patients take prolonged hot baths or showers, often lasting 1 to 3 hours, specifically to relieve nausea and vomiting. The water temperature is characteristically as hot as tolerable.
• Multiple sessions per day: During active emetic episodes, patients may bathe 5 to 10 or more times per day, spending the majority of the episode in the bathroom.
• Immediate symptom relief: Patients consistently report that hot water immersion produces rapid (within minutes) and marked relief of nausea, though symptoms return soon after exiting the bath or shower.
• Learned behavior: Patients discover the hot-water relief effect independently and develop a compulsive pattern of bathing as a self-treatment strategy. Many patients are able to describe exactly when they discovered this remedy.
• Interference with daily function: The time spent bathing during active episodes is substantial and interferes with work, social activities, and sleep. Some patients report scalding injuries from excessively hot water.

Proposed Mechanisms for Hot Water Relief

The mechanism by which hot water immersion relieves CHS symptoms is not definitively established, but several hypotheses have been proposed:

• TRPV1 receptor activation: Transient receptor potential vanilloid 1 (TRPV1) receptors, which are activated by both capsaicin and heat (>43 degrees C), are expressed on visceral afferent neurons in the gastrointestinal tract and in the central nervous system. Hot water activates cutaneous TRPV1 receptors, which may produce a counter-irritant or competing sensory signal that attenuates the nausea mediated by visceral TRPV1 activation. This hypothesis is supported by the observation that topical capsaicin (which also activates TRPV1) has been reported to relieve CHS symptoms.
• Thermoregulatory redistribution of blood flow: Hot water immersion causes peripheral vasodilation and redistribution of blood flow from the splanchnic circulation to the cutaneous circulation. Reduced splanchnic blood flow may decrease gastrointestinal motility and sensory input, attenuating nausea.
• Hypothalamic effects: Cannabinoids influence thermoregulation through hypothalamic CB1 receptors. CHS may involve hypothalamic thermoregulatory dysfunction, and external heat application may compensate for this dysregulation.

Pathophysiology of CHS

The pathophysiology of CHS is incompletely understood but is believed to involve a complex interaction between the exogenous cannabinoids from chronic cannabis use and the endogenous endocannabinoid system that regulates gastrointestinal motility, nausea, and vomiting.

The Cannabis Paradox: Antiemetic Becomes Emetogenic

Cannabis contains over 100 identified cannabinoids, of which delta-9-tetrahydrocannabinol (THC) is the most pharmacologically active. At typical doses, THC acts as an antiemetic by activating CB1 receptors in the brainstem vomiting centers (nucleus tractus solitarius, area postrema) and in the enteric nervous system. This antiemetic property is the basis for the clinical use of dronabinol and nabilone as antiemetic agents in chemotherapy-induced nausea and vomiting.

The paradox of CHS is that chronic, heavy cannabis exposure eventually produces the opposite effect: severe, intractable vomiting. Several mechanisms have been proposed to explain this paradox:

Desensitization and Downregulation of Central CB1 Receptors

Chronic exposure to exogenous cannabinoids leads to progressive desensitization and downregulation of CB1 receptors in the brain, particularly in areas involved in nausea and vomiting regulation. As central CB1 signaling becomes impaired, the antiemetic effects of cannabis diminish. Eventually, the loss of central CB1-mediated antiemesis may unmask or be overwhelmed by pro-emetic effects mediated through other pathways.

Peripheral CB1 Receptor Effects on Gastric Motility

In the enteric nervous system, CB1 receptor activation inhibits gastric motility and slows gastric emptying. With chronic high-dose cannabis use, paradoxical effects on gastric motility may develop, including gastric stasis and dysmotility that trigger nausea and vomiting through mechanoreceptor activation and vagal afferent stimulation. Some studies have demonstrated delayed gastric emptying during CHS episodes, which normalizes after cannabis cessation.

Hypothalamic-Pituitary Axis Disruption

The hypothalamus, which contains a high density of CB1 receptors, plays a central role in regulating nausea, thermoregulation, and stress responses. Chronic cannabinoid overstimulation may disrupt hypothalamic function, contributing to both the emetic episodes and the thermoregulatory dysfunction (the intense desire for hot water) that characterizes CHS.

Genetic Susceptibility

Not all heavy, chronic cannabis users develop CHS; in fact, the majority do not. This observation suggests a genetic susceptibility component. Polymorphisms in genes encoding cannabinoid receptors (CNR1, CNR2), endocannabinoid-metabolizing enzymes (FAAH, MAGL), hepatic cytochrome P450 enzymes involved in THC metabolism (CYP2C9, CYP3A4), and TRPV1 receptors have been proposed as potential genetic modifiers, though no specific genetic marker has been validated for CHS risk prediction.

Accumulation of Lipophilic Cannabinoids

THC and its metabolites are highly lipophilic and accumulate in adipose tissue with chronic use. During periods of stress, fasting, or lipolysis, stored cannabinoids may be released from fat stores back into the circulation, producing unpredictable fluctuations in cannabinoid levels that may trigger emetic episodes. This "mobilization" hypothesis could explain why CHS episodes often occur during fasting or periods of physiological stress and why resolution after cannabis cessation requires weeks (the time needed for tissue stores to be depleted).

Epidemiology

The epidemiology of CHS has evolved rapidly alongside the changing landscape of cannabis legalization and use patterns worldwide.

Prevalence

• Studies in emergency department populations in states with legalized cannabis have found that 6 to 33 percent of patients presenting with recurrent vomiting meet criteria for CHS.
• Among self-identified regular cannabis users surveyed in primary care and emergency department settings, approximately 25 to 33 percent report experiencing vomiting symptoms that may be consistent with CHS, though many do not meet full Rome IV criteria.
• Emergency department visits for cyclic vomiting have increased significantly in regions that have legalized recreational cannabis, with some studies reporting a near-doubling of such visits in the years following legalization.

Demographics

• Age: CHS most commonly presents in young adults between 20 and 40 years of age, corresponding to the peak demographic for heavy cannabis use. However, it has been described across a wide age range, from adolescents to older adults.
• Sex: Most case series report a male predominance (approximately 60 to 70 percent male), likely reflecting the higher prevalence of heavy cannabis use among men.
• Cannabis use history: The median duration of cannabis use before CHS onset is approximately 3 to 5 years of daily or near-daily use, though cases have been reported after as little as 1 year and as long as 20 or more years of use.

Impact of Cannabis Legalization

The legalization of recreational cannabis in multiple US states and other jurisdictions has been associated with increased CHS incidence, likely driven by several factors: increased overall cannabis use prevalence, increased access to high-potency products (concentrates with THC content exceeding 80 to 90 percent), normalization and de-stigmatization of heavy daily use, and the perception that cannabis is entirely safe. Emergency department visits coded for CHS-related diagnoses have risen substantially in Colorado, Washington, California, and other legalized states.

Clinical Phases of CHS

The natural history of CHS in patients who continue to use cannabis follows a characteristic three-phase pattern that often repeats cyclically over months to years.

Phase	Duration	Key Features
Prodromal Phase	Hours to days before emesis onset	Early-morning nausea, epigastric discomfort, anorexia, anxiety, fear of impending episode. Patients may increase cannabis use to self-treat, paradoxically worsening the cycle.
Hyperemetic Phase	24 to 48 hours (up to 7-10 days)	Intense, protracted vomiting (up to dozens of times per day), severe nausea, abdominal pain, dehydration, compulsive hot bathing, frequent ED visits. This is the phase that prompts medical attention.
Recovery Phase	Days to weeks	Gradual resolution of vomiting, return of appetite, resumption of normal activities. Patients are typically asymptomatic between episodes if cannabis use continues.

Without cannabis cessation, this cycle repeats at intervals ranging from weekly to monthly. With each subsequent episode, the hyperemetic phase may become more severe and more resistant to symptomatic treatment, and the inter-episode intervals may shorten.

Differential Diagnosis

CHS must be distinguished from other causes of recurrent episodic vomiting, several of which share overlapping clinical features.

Cyclical Vomiting Syndrome (CVS)

CVS is the single most important differential diagnosis for CHS, as the two conditions are clinically nearly indistinguishable during active episodes. The distinguishing factors are:

Feature	CHS	CVS
Cannabis use	Required: prolonged, heavy use precedes symptoms	May use cannabis (for symptom relief) but not causative
Response to cannabis cessation	Episodes resolve completely	Episodes persist despite cessation
Pathological bathing	Present in 70-90%	Rare (<10%)
Age of onset	Typically 20-40 years (adult onset)	Often childhood onset with potential persistence into adulthood
Family history of migraine	No specific association	Strong association (up to 80% in pediatric CVS)
Response to migraine prophylaxis (amitriptyline, topiramate)	Ineffective (if cannabis use continues)	Effective in 50-70% of patients

The diagnostic challenge is compounded by the fact that some CVS patients use cannabis specifically to treat their nausea and vomiting symptoms, creating a scenario in which cannabis use is secondary to, rather than causative of, the vomiting. In these cases, a trial of cannabis cessation is essential: if episodes resolve, the diagnosis shifts to CHS; if episodes persist, CVS is confirmed.

Gastroparesis

Gastroparesis produces nausea, vomiting, bloating, early satiety, and abdominal pain, and can be confused with CHS, particularly since cannabis itself can slow gastric emptying. Key distinguishing features include: gastroparesis symptoms are typically postprandial and chronic (not episodic), vomiting characteristically contains recognizable food eaten hours earlier, and gastric emptying studies demonstrate objective delay. However, CHS and gastroparesis can coexist, and cannabis-induced gastroparesis has been described.

Gastroesophageal Reflux Disease (GERD)

Severe GERD can produce nausea and vomiting, but it is typically associated with heartburn, acid regurgitation, and esophageal symptoms rather than the stereotypical episodic pattern of CHS. Vomiting from GERD is usually postprandial and positional, not cyclical.

Peptic Ulcer Disease and Upper GI Obstruction

Gastric outlet obstruction from peptic ulcer disease can cause recurrent vomiting that resolves between obstructive episodes. Endoscopy and imaging readily distinguish structural causes from CHS.

Pregnancy (Hyperemesis Gravidarum)

In women of reproductive age presenting with recurrent vomiting, pregnancy must always be excluded. Hyperemesis gravidarum shares several features with CHS, including severe nausea, protracted vomiting, and dehydration. A pregnancy test should be obtained in all female patients of childbearing age presenting with recurrent vomiting.

Increased Intracranial Pressure

Central causes of vomiting, including intracranial mass lesions, hydrocephalus, and pseudotumor cerebri, can produce episodic vomiting (particularly morning vomiting). The presence of headache, papilledema, focal neurological deficits, or personality changes should prompt neuroimaging.

Adrenal Insufficiency

Addisonian crisis and chronic adrenal insufficiency can present with recurrent nausea, vomiting, and abdominal pain. Morning cortisol and cosyntropin stimulation testing should be considered when the clinical picture is atypical for CHS.

Metabolic Causes

• Diabetic ketoacidosis: Can cause severe nausea, vomiting, and abdominal pain, particularly in young adults with type 1 diabetes.
• Acute intermittent porphyria: Episodic abdominal pain and vomiting in young adults, often triggered by fasting or hormonal changes.
• Uremia: Advanced chronic kidney disease produces chronic nausea and vomiting.

The Diagnostic Challenge: Cannabis Use Disclosure

A major barrier to timely CHS diagnosis is patient non-disclosure of cannabis use. Patients may not volunteer their cannabis use history for several reasons:

• Social stigma, particularly in jurisdictions where cannabis remains illegal
• Belief that cannabis is "natural" and therefore harmless, leading patients to dismiss it as medically relevant
• Unawareness that cannabis can cause vomiting (the paradox is counterintuitive to most users)
• Reluctance to consider that their preferred substance is the cause of their suffering
• Use of cannabis specifically to self-treat the nausea, creating cognitive dissonance about its role

Clinicians should routinely and non-judgmentally ask about cannabis use in all patients presenting with recurrent vomiting. Framing the question in terms of frequency, route of administration, and product type (rather than simply "do you use marijuana?") tends to elicit more complete information. Urine drug screening can confirm recent cannabis use when clinical suspicion is high and the history is uncertain, though a positive test alone does not confirm CHS.

Emergency Department Management of Acute CHS Episodes

Patients with CHS frequently present to the emergency department during the hyperemetic phase with severe dehydration, electrolyte abnormalities, and intractable vomiting. Acute management focuses on symptom control, volume resuscitation, and initiation of the diagnostic process.

Intravenous Fluid Resuscitation

Aggressive crystalloid administration (normal saline or lactated Ringer's solution) is first-line therapy for the dehydration that accompanies CHS episodes. Patients may require 2 to 4 liters or more of intravenous fluids during the initial resuscitation. Electrolytes (potassium, magnesium, calcium, phosphorus) should be monitored and repleted as needed, as protracted vomiting frequently produces hypokalemia, hypomagnesemia, and metabolic alkalosis.

Antiemetic Therapy

Standard antiemetic agents have variable and often limited efficacy in CHS. The response to antiemetics in CHS differs from that seen in other vomiting syndromes:

Agent	Class	Efficacy in CHS
Ondansetron	5-HT3 antagonist	Limited; often ineffective or provides only modest relief. This poor response to ondansetron is itself a clinical clue to CHS.
Promethazine, prochlorperazine	Dopamine antagonists / phenothiazines	Moderate; may provide partial relief but often insufficient alone.
Haloperidol (0.5-2 mg IV)	Butyrophenone / D2 antagonist	Good; increasingly recognized as one of the most effective acute antiemetics for CHS. Low doses are usually sufficient.
Droperidol (0.625-1.25 mg IV)	Butyrophenone / D2 antagonist	Good; similar to haloperidol. Requires QTc monitoring.
Topical capsaicin (0.075% cream)	TRPV1 agonist	Good to excellent; applied to the periumbilical area. Activates the same TRPV1 pathway as hot water. Increasingly used as a first-line adjunct.
Benzodiazepines (lorazepam 1-2 mg IV)	GABA-A agonist	Moderate; may reduce anxiety-driven nausea amplification and provide sedation during severe episodes.

Topical Capsaicin

Topical capsaicin (0.075% cream applied to the periumbilical abdomen) has emerged as a distinctive and effective adjunctive therapy for acute CHS episodes. The mechanism is believed to involve activation of cutaneous TRPV1 receptors, mimicking the thermoreceptor activation produced by hot bathing. Multiple case reports and small series have described rapid symptom improvement with capsaicin application. Its favorable safety profile and ease of use make it an attractive first-line adjunct in the emergency department.

Long-Term Management: Cannabis Cessation

The definitive treatment for CHS is complete and sustained cessation of all cannabis products. This is the only intervention that produces lasting remission of emetic episodes. All other treatments, including antiemetics, hot bathing, and capsaicin, provide only temporary symptomatic relief without addressing the underlying cause.

Counseling and Motivational Interviewing

Many CHS patients are ambivalent about cannabis cessation. Motivational interviewing techniques that explore the patient's own reasons for considering cessation, acknowledge the difficulty of behavior change, and build intrinsic motivation are more effective than directive advice or scare tactics. Key counseling points include:

• CHS will recur with continued cannabis use and may worsen over time
• No medication can prevent CHS episodes while cannabis use continues
• Symptoms typically resolve within 1 to 3 months of complete abstinence
• Even a single relapse into cannabis use can trigger a recurrent episode
• Successful cessation eliminates the need for repeated emergency department visits and costly workups

Cannabis Use Disorder Treatment

Many CHS patients meet DSM-5 criteria for cannabis use disorder, which is defined by impaired control over use, social impairment, risky use, and/or pharmacological tolerance and withdrawal. Treatment options include:

• Cognitive behavioral therapy (CBT): The most evidence-based psychotherapy for cannabis use disorder. Helps patients identify triggers for use, develop coping strategies, and manage cravings.
• Motivational enhancement therapy: A brief, structured intervention that strengthens the patient's internal motivation for change.
• Contingency management: Provides tangible rewards for verified abstinence (negative urine drug tests).
• Pharmacotherapy: No FDA-approved medication exists specifically for cannabis use disorder, but several agents are under investigation (gabapentin, N-acetylcysteine, oxytocin). N-acetylcysteine has shown the most promise in adolescents.
• Cannabis withdrawal management: Cannabis withdrawal syndrome (irritability, anxiety, insomnia, decreased appetite, restlessness, depressed mood) occurs in approximately 50 percent of daily users who abruptly discontinue. Symptoms typically peak within the first week and resolve by 2 to 4 weeks. Supportive management (sleep hygiene, exercise, short-term use of non-addictive anxiolytics or sleep aids) can improve tolerance of the withdrawal period.

Complications of CHS

While CHS is not inherently life-threatening, repeated severe emetic episodes can produce serious complications:

• Severe dehydration and acute kidney injury: Prolonged vomiting with inadequate fluid intake can produce prerenal acute kidney injury. Rhabdomyolysis from prolonged hot-water immersion has also been reported.
• Electrolyte abnormalities: Hypokalemia, hyponatremia, hypochloremic metabolic alkalosis, and hypomagnesemia from protracted vomiting can cause cardiac arrhythmias, muscle weakness, and seizures.
• Mallory-Weiss tears: Forceful, repeated vomiting can cause mucosal lacerations at the gastroesophageal junction, presenting as hematemesis.
• Boerhaave syndrome: Although rare, esophageal perforation from severe retching has been reported in CHS patients and represents a life-threatening surgical emergency.
• Dental erosion: Chronic exposure of dental enamel to gastric acid from repeated vomiting produces progressive dental erosion, particularly affecting the lingual surfaces of the upper anterior teeth.
• Malnutrition and weight loss: Frequent emetic episodes with prolonged periods of anorexia can produce clinically significant weight loss and nutritional deficiencies.
• Thermal burns: Compulsive hot-water bathing at extreme temperatures can cause first- and second-degree thermal burns.
• Psychosocial consequences: Repeated emergency department visits, missed work, social isolation, and the frustration of recurrent unexplained illness take a significant toll on mental health and social functioning.

CHS vs. CVS: The Diagnostic Overlap and the Cannabis Question

The relationship between CHS and CVS is one of the most debated topics in functional gastroenterology. The two conditions share a nearly identical clinical phenotype, raising the question of whether CHS is truly a distinct entity or simply CVS triggered by cannabis in susceptible individuals.

Arguments for CHS as a distinct entity include:

• The definitive response to cannabis cessation (CVS does not resolve with cannabis cessation)
• The high prevalence of pathological bathing behavior (uncommon in CVS)
• The absence of the migraine association that characterizes CVS
• The different age of onset (CHS in young adults; CVS often begins in childhood)
• The poor response to standard CVS prophylaxis (amitriptyline, topiramate) when cannabis use continues

Arguments for a shared pathophysiology include:

• The identical episodic pattern (prodrome, hyperemesis, recovery)
• Some CVS patients use cannabis and may be misclassified as CHS
• Some CHS patients continue to have occasional episodes even after verified cannabis cessation, suggesting an underlying CVS predisposition
• Both conditions may involve shared genetic susceptibility in the endocannabinoid system or mitochondrial pathways

The practical approach, as codified by Rome IV, is pragmatic: if the vomiting resolves with cannabis cessation, the diagnosis is CHS; if it persists despite cessation, the diagnosis is CVS. A cannabis cessation trial is therefore not just therapeutic but diagnostically essential.

Special Populations

Adolescents

CHS is increasingly recognized in adolescents as cannabis use among teenagers remains prevalent. The diagnosis may be particularly challenging in this age group due to reluctance to disclose substance use to parents or healthcare providers. Pediatric and adolescent medicine clinicians should maintain a high index of suspicion for CHS in teenagers presenting with recurrent vomiting and should create a confidential environment for substance use screening.

Pregnant Patients

Cannabis use during pregnancy is increasing, with some women using it specifically to treat pregnancy-related nausea. CHS during pregnancy presents a diagnostic challenge, as hyperemesis gravidarum is a common alternative explanation for severe vomiting in pregnancy. However, the presence of pathological bathing behavior, a history of pre-pregnancy CHS episodes, and a cannabis use history exceeding typical pregnancy-related use should raise suspicion. Cannabis cessation is strongly recommended during pregnancy for both CHS management and fetal safety.

Patients Using Synthetic Cannabinoids

Synthetic cannabinoids (K2, Spice, and related products) are potent CB1 receptor agonists that have been associated with a CHS-like syndrome. Because synthetic cannabinoids are often more potent and have longer half-lives than natural THC, the hyperemetic syndrome they produce may be more severe and more resistant to treatment. Standard urine drug screens may not detect synthetic cannabinoids, requiring specialized testing when clinical suspicion is high.

Medical Cannabis Users

Patients who use cannabis for legitimate medical indications (chronic pain, epilepsy, chemotherapy-induced nausea, multiple sclerosis spasticity) face a particularly difficult dilemma when they develop CHS. The treating clinician must weigh the benefits of continued medical cannabis use against the morbidity of recurrent CHS episodes. In most cases, the severity of CHS warrants cessation, with alternative therapies substituted for the medical indication.

Historical Context

CHS was first formally described in 2004 by Allen and colleagues, who published a case series of 19 patients in South Australia with recurrent vomiting and heavy cannabis use, 10 of whom achieved remission with cannabis cessation. Before this description, CHS was likely misdiagnosed as CVS, psychogenic vomiting, or unexplained recurrent vomiting in many patients.

The recognition of CHS expanded rapidly in the following decade, driven by increasing cannabis potency, expanding legalization, and growing clinical awareness. The inclusion of CHS in the Rome IV classification in 2016 represented a formal acknowledgment of the entity by the global gastroenterology community and provided the first standardized diagnostic criteria.

Limitations of the Rome IV Criteria for CHS

• Retrospective confirmation bias: Criterion 3 (relief with cannabis cessation) is often assessed retrospectively based on patient report, which is subject to recall bias and placebo effect. Prospective confirmation requires a period of verified abstinence that many patients find difficult to achieve.
• Difficulty verifying abstinence: Self-reported cannabis cessation is unreliable. Urine drug testing can confirm recent use but cannot distinguish heavy from light use or determine whether the patient has achieved the sustained complete abstinence needed for symptom resolution. Urine THC metabolites can remain positive for 2 to 4 weeks (or longer in heavy users) after true cessation.
• No dose or duration thresholds: The criterion "prolonged, excessive cannabis use" lacks specific quantitative thresholds. There is no defined minimum amount or duration of use required, making the criterion somewhat subjective and dependent on clinical judgment.
• Overlap with CVS in cannabis users: Patients with true CVS who also use cannabis may be misdiagnosed with CHS. If they happen to stop cannabis use coincidentally during a natural CVS remission period, the apparent resolution of symptoms may be falsely attributed to cannabis cessation.
• Temporal criteria may delay diagnosis: Requiring 3 months of symptom duration and 6 months of symptom onset can delay formal diagnosis in patients presenting early in the course of CHS. However, clinical suspicion should still be high even before formal criteria are met.
• Pathological bathing is only supportive: Despite being one of the most distinctive and recognizable features of CHS, pathological bathing behavior is classified as a supportive rather than required criterion. In practice, its presence substantially increases diagnostic confidence and should be actively sought in the history.
• Evolving cannabis landscape: The Rome IV criteria were developed when smoked cannabis flower was the predominant form of use. The dramatic increase in high-potency concentrates, edibles, and synthetic cannabinoids since 2016 may alter the clinical presentation and time course of CHS in ways not anticipated by the original criteria.

Practical Pearls for Clinical Use

• Ask every patient with recurrent vomiting about cannabis use. This should be a routine screening question, not reserved for patients who "look like" cannabis users. CHS occurs across all demographics.
• Ask about hot bathing specifically. "Do you find that hot showers or baths help your nausea?" is a single question that, when answered affirmatively in a cannabis user with recurrent vomiting, essentially makes the diagnosis. Many patients will not volunteer this information unless specifically asked.
• Poor response to ondansetron is a clinical clue. When a patient with recurrent vomiting does not respond to ondansetron (which is highly effective for most other causes of emesis), CHS should move up on the differential diagnosis.
• Try topical capsaicin in the emergency department. Applying 0.075% capsaicin cream to the periumbilical abdomen is a simple, low-risk intervention that can provide rapid symptom relief in CHS. A positive response to capsaicin further supports the diagnosis.
• Consider low-dose haloperidol early. Haloperidol (0.5 to 2 mg IV) has shown superior efficacy to traditional antiemetics in acute CHS episodes. Its early use can reduce ED length of stay and improve patient comfort.
• Do not diagnose CHS after a single episode. The Rome IV criteria require a chronic, stereotypical pattern. A single vomiting episode in a cannabis user may represent an unrelated viral illness, food poisoning, or other acute cause. However, the possibility of CHS should be documented and the patient counseled to monitor for recurrence.
• Minimize unnecessary testing in classic presentations. When the clinical picture is classic (young adult, daily cannabis use for years, stereotypical episodic vomiting, hot-water bathing, poor response to ondansetron), extensive diagnostic testing is unlikely to reveal an alternative diagnosis and delays the critical therapeutic step: cannabis cessation counseling.
• Recommend a minimum 2 to 4-week abstinence trial. Explain to the patient that THC takes weeks to clear from the body and that a brief reduction in use is insufficient. Complete abstinence for at least 2 to 4 weeks (ideally 1 to 3 months) is needed to assess response. Verified abstinence with urine drug testing strengthens the diagnostic assessment.
• Anticipate and manage cannabis withdrawal. Warn patients that irritability, insomnia, decreased appetite, and anxiety may occur during the first 1 to 2 weeks of abstinence. Providing supportive strategies (sleep hygiene, physical activity, short-term sleep aids) increases the likelihood of successful cessation.
• Warn about relapse. Patients should understand that even occasional cannabis use after a period of remission can trigger a recurrent CHS episode, sometimes within the first one or two uses. Complete, lifelong abstinence is the only reliable way to prevent recurrence.
• Document the diagnosis clearly. Recording "Cannabinoid Hyperemesis Syndrome (Rome IV B3c)" in the medical record ensures that the diagnosis is visible to all future providers and reduces the likelihood of repeated unnecessary workups during future emergency department presentations.
• Address the paradox directly with patients. Many patients struggle to accept that cannabis, which they perceive as helping their nausea, is in fact the cause of their vomiting. Acknowledging this paradox openly, explaining the proposed mechanism (chronic use desensitizes the very receptors that produce the antiemetic effect), and framing cannabis cessation as a diagnostic and therapeutic trial rather than a judgment can improve patient receptiveness.