What is cannabis hyperemesis syndrome?

What is Cannabis Hyperemesis Syndrome?

Cannabis Hyperemesis Syndrome (CHS) is a condition of recurrent, stereotypical episodes of severe nausea and vomiting that occurs in chronic, heavy cannabis users and resolves only with complete and sustained cannabis cessation. 1, 2

Clinical Definition and Diagnostic Criteria

CHS is characterized by three essential diagnostic features that must all be present: 1, 2

• Stereotypical episodic vomiting occurring ≥3 times annually with acute onset and duration typically less than 1 week per episode 1, 2
• Prolonged cannabis exposure with >1 year of regular use before symptom onset and frequency >4 times per week 1, 2
• Complete symptom resolution after at least 6 months of continuous cannabis abstinence (or duration equal to at least 3 typical vomiting cycles for that specific patient) 1, 2

The syndrome presents with cyclic episodes of intense nausea, intractable vomiting, and abdominal pain that occur during active, ongoing cannabis use—not after stopping. 1

Pathognomonic Clinical Feature

Compulsive hot water bathing or showering is the hallmark behavioral feature of CHS, reported in 44-71% of cases. 1, 3 Patients exhibit pathological use of hot showers or baths for temporary symptom relief, often spending hours in scalding water. 1, 3 However, this behavior is not exclusively diagnostic, as it also occurs in 44% of cyclic vomiting syndrome cases. 3

Underlying Pathophysiology

The syndrome results from dysregulation of the endocannabinoid system's control over emesis: 3, 4

• CB1 receptors are densely distributed in the dorsal vagal complex, the critical brain area controlling emesis 3
• Chronic high-dose THC exposure causes loss of negative feedback on the hypothalamic-pituitary-adrenal axis, resulting in increased vagal nerve discharges that trigger vomiting 3
• Cannabis exhibits a biphasic effect: antiemetic at low doses but pro-emetic at higher chronic doses 4
• Altered gastric motility and emptying occur through peripheral CB1 receptor activation 3

Risk Factors and High-Risk Populations

Patients at highest risk for developing CHS include those with: 1

• Daily cannabis consumption, which occurred in 68% of confirmed CHS cases 3
• Consumption of >1.5 g/day of inhaled cannabis 1
• Use of >20 mg/day of THC-dominant cannabis oil 1
• Cannabis use >2-3 times daily with products of unknown THC/CBD content 1
• Modern high-potency cannabis products with dramatically elevated THC concentrations compared to historical formulations 3

The route of administration does not matter—edible cannabis causes CHS just as effectively as smoking or vaping, because total THC dose and duration of exposure are the critical factors, not the delivery method. 3

Critical Distinction from Cannabis Withdrawal Syndrome

CHS must be differentiated from Cannabis Withdrawal Syndrome (CWS), as they require opposite management strategies despite both causing vomiting: 1

• CHS: Vomiting occurs during active chronic cannabis use; treatment requires cessation 1
• CWS: Vomiting occurs after stopping cannabis (24-72 hours post-cessation); may require supportive care or cannabinoid substitution 1

Diagnostic Biomarker

Urinary THC-COOH (carboxy-THC) concentrations measured by gas chromatography mass-spectrometry can support the diagnosis: 5

• CHS patients typically exhibit urinary THC-COOH levels >100 ng/mL (laboratory cutoff is 3.0 ng/mL) 5
• In one adolescent/young adult case series, 14 of 15 CHS patients had levels >100 ng/mL, with seven exceeding 500 ng/mL 5
• This biomarker indicates significant chronic cannabis exposure and can help guide diagnostic evaluation, reducing unnecessary workup 5

Clinical Burden and Diagnostic Challenges

CHS is frequently underdiagnosed or misdiagnosed due to limited clinician awareness, leading to: 1, 3

• Extensive unnecessary diagnostic testing including repeated endoscopies, imaging, and laboratory workups 1
• Average diagnostic delay of several years 1
• Frequent emergency department visits and significant healthcare system burden 4
• Patient denial of the cannabis-symptom link, as many attribute vomiting to food, alcohol, or stress 1

When esophagogastroduodenoscopy is performed soon after a CHS episode, findings such as mild gastritis, erythematous streaking, Mallory-Weiss tears, or esophagitis are consequences of vomiting, not primary pathology. 1

Definitive Treatment

Complete and permanent cannabis cessation is the only curative treatment for CHS. 1, 2, 3 Key management principles include:

• Symptom resolution requires at least 6 months of continuous abstinence or duration equal to 3 typical vomiting cycles 1, 2
• Partial reduction of cannabis use or switching to edible forms does not lead to symptom improvement; full abstinence is mandatory 1
• Relapse rates exceed 40% in reported series, underscoring the need for ongoing addiction medicine support 1
• Tricyclic antidepressants (amitriptyline 75-100 mg at bedtime) serve as the mainstay of long-term preventive pharmacotherapy 1, 2, 3