What is cannabis hyperemesis syndrome in a young to middle-aged adult with a long history of heavy cannabis use, presenting with severe vomiting, abdominal pain, and weight loss?

What is Cannabis Hyperemesis Syndrome?

Cannabis hyperemesis syndrome (CHS) is a paradoxical condition occurring in chronic, heavy cannabis users characterized by stereotypical cyclic episodes of severe nausea, vomiting, and abdominal pain that are temporarily relieved by compulsive hot water bathing, with complete resolution only achieved through sustained cannabis cessation. 1

Clinical Presentation

CHS presents with a distinctive triad of features that distinguish it from other causes of cyclic vomiting:

• Stereotypical episodic vomiting occurring at least 3 times annually, with acute onset and duration typically less than 1 week 1, 2
• Severe abdominal pain often with morning predominance, accompanied by significant weight loss from recurrent episodes 1, 3
• Pathognomonic hot water bathing behavior where patients compulsively take hot showers or baths for symptom relief, present in 44-71% of cases 4, 2

The syndrome occurs exclusively in young to middle-aged adults (typically under 50 years) with prolonged cannabis exposure 1, 3.

Required Cannabis Exposure Pattern

CHS requires specific cannabis use criteria to establish the diagnosis:

• Duration of use >1 year before symptom onset 1, 2
• Frequency >4 times weekly on average, with particularly high risk in those consuming >1.5 g/day of inhaled cannabis or >20 mg/day of THC-dominant products 1, 4
• The syndrome occurs regardless of route of administration—smoking, vaping, or edibles all deliver sufficient THC systemically to trigger CHS 2

Pathophysiology

The mechanism involves paradoxical dysregulation of the endocannabinoid system after chronic high-dose THC exposure:

• CB1 receptors densely distributed in the dorsal vagal complex become dysregulated, losing their normal antiemetic function and instead promoting emesis 2, 5
• Loss of negative feedback on the hypothalamic-pituitary-adrenal axis results in increased vagal nerve discharges contributing to vomiting 2
• Altered gastric motility occurs through peripheral CB1 receptor activation 2
• Cannabinoids produce a biphasic effect where low doses are antiemetic but high chronic doses become proemetic 5

Diagnostic Criteria

The definitive diagnosis requires all three of the following elements:

• Stereotypical episodic vomiting (≥3 episodes annually) 1
• Cannabis use pattern meeting the exposure criteria above 1
• Complete symptom resolution after at least 6 months of continuous cannabis abstinence, or abstinence duration equal to at least 3 typical vomiting cycles for that patient 1, 4, 2

This last criterion—sustained symptom resolution with abstinence—is the only reliable feature that definitively separates CHS from cyclic vomiting syndrome (CVS), as both conditions present identically during acute episodes. 2

Critical Diagnostic Pitfall

CHS remains severely underdiagnosed despite being described over 15 years ago, leading to extensive medical wandering with repeated, expensive, and sometimes invasive investigations 6, 3, 7. The syndrome is frequently missed because:

• Limited clinician awareness of the condition 6
• Patients may not volunteer cannabis use history unless specifically asked 6
• Hot water bathing behavior, while highly suggestive, also occurs in 44% of CVS patients and is not pathognomonic 2

Always rule out life-threatening conditions first (acute abdomen, bowel obstruction, mesenteric ischemia, pancreatitis, myocardial infarction) before attributing symptoms solely to CHS 1, 2.

Distinction from Cannabis Withdrawal Syndrome

CHS must be differentiated from cannabis withdrawal syndrome, as they present oppositely but both can cause vomiting:

• CHS: Vomiting occurs during active chronic cannabis use 4
• Cannabis withdrawal syndrome: Vomiting occurs after stopping cannabis use, with symptoms beginning 24-72 hours after cessation and resolving within 1-2 weeks 4

Definitive Treatment

Complete and permanent cessation of all cannabis use is the only intervention that leads to long-term resolution of CHS symptoms—there is no alternative definitive treatment. 1, 7

• Symptoms require at least 6 months of continuous abstinence for complete resolution, or duration equal to 3 typical vomiting cycles 1, 4
• Patients must be counseled that any resumption of cannabis use will trigger symptom recurrence 8
• A minimum of 3 months cessation is needed to even begin seeing symptom improvement and confirm the diagnosis 8