What are the likely underlying etiologies for a patient with cyclic vomiting, episodic nausea, abdominal pain, tachycardia, anxiety, and psychotic‑like symptoms who denies cannabis use?

Differential Diagnosis for Cyclic Vomiting Without Cannabis Use

When a patient presents with cyclic vomiting, episodic nausea, abdominal pain, tachycardia, anxiety, and psychotic-like symptoms but denies cannabis use, the primary diagnosis is Cyclic Vomiting Syndrome (CVS), and you must systematically evaluate for its common comorbidities and triggers. 1

Core Diagnostic Framework

The Rome IV criteria for CVS require stereotypical episodes of vomiting with acute onset and duration less than 1 week, at least 3 discrete episodes in the previous year and 2 episodes in the past 6 months occurring at least 1 week apart, and absence of nausea and vomiting between episodes. 1

Key Clinical Features to Assess

• Episodic pattern: CVS is characterized by discrete vomiting episodes separated by completely asymptomatic periods, though approximately 15% of patients experience episodes lasting longer than 7 days. 1

• Hot water bathing behavior: Approximately 48% of CVS patients who do NOT use cannabis find relief from hot bathing or showering, so this behavior is not pathognomonic for cannabinoid hyperemesis syndrome and should not mislead you. 1

• Severity stratification: Patients with fewer than 4 episodes per year, each lasting less than 2 days without ED visits, have mild CVS; those with 4 or more episodes per year lasting more than 2 days requiring ED visits have moderate-severe CVS. 1

Essential Comorbid Conditions to Evaluate

Psychiatric Comorbidities (Most Common)

Mood disorders are present in 50-60% of adult CVS patients and must be systematically assessed. 1

• Anxiety disorders: Including generalized anxiety, panic disorder, and depression collectively affect the majority of CVS patients. 1

• Psychotic-like symptoms: The anxiety and panic features in CVS can manifest as severe distress that may appear psychotic, particularly during acute episodes. 1

Neurological Associations

• Migraine headaches: Present in 20-30% of adult CVS patients, and a personal or family history of migraine is a supportive diagnostic criterion in Rome IV. 1

• Seizure disorders: Occur in approximately 3% of CVS patients, suggesting shared pathophysiological mechanisms across episodic conditions. 1

Autonomic Dysfunction

Postural orthostatic tachycardia syndrome (POTS) is observed in a substantial subgroup of CVS patients and directly explains the tachycardia you describe. 1

• Autonomic imbalances may relate to the underlying pathophysiologic mechanisms of CVS. 1

• Treating POTS can improve patients' overall functional status and may decrease CVS episode frequency. 1

Critical Diagnostic Pitfalls

Rule Out Life-Threatening Conditions First

Before confirming CVS, you must exclude acute abdomen, bowel obstruction, mesenteric ischemia, pancreatitis, and myocardial infarction. 2, 3

Verify Cannabis Abstinence

• Patient denial is common: Many patients attribute vomiting to food, alcohol, or stress rather than cannabis, which can impede appropriate diagnosis. 3

• Definitive distinction: Complete and persistent resolution of all symptoms after at least 6 months of continuous cannabis abstinence is the only reliable criterion that separates CHS from CVS. 2

• If the patient truly has no cannabis exposure, CVS is the diagnosis; if they are concealing use, symptoms will only resolve with 6+ months of abstinence. 2, 3

Cannabis Withdrawal Syndrome Consideration

• Cannabis withdrawal syndrome occurs in approximately 47% of regular cannabis users after cessation, with symptoms including anxiety, irritability, insomnia, and gastrointestinal symptoms beginning 24-72 hours after cessation and peaking between days 2-6. 1, 3

• If the patient recently stopped cannabis (even if denying current use), withdrawal could explain some symptoms, but withdrawal does not cause cyclic vomiting—it causes symptoms AFTER stopping, not during active use. 3

Management Algorithm for CVS

Acute Episode Treatment

• Benzodiazepines: Lorazepam 0.5-2 mg every 4-6 hours provides both antiemetic effects and addresses the anxiety component. 2, 3

• Antipsychotics: Haloperidol or promethazine can be used as second-line agents. 2, 3

• Avoid opioids entirely: They worsen nausea, carry high addiction risk, and do not address underlying pathophysiology. 2, 3

Long-Term Prophylaxis

Tricyclic antidepressants, specifically amitriptyline, are the mainstay of preventive therapy for CVS. 1, 2, 3

• Start at 25 mg at bedtime and titrate weekly by 25 mg increments to reach a minimal effective dose of 75-100 mg. 2, 3

• This addresses both the CVS episodes and the common comorbid anxiety and depression. 1

Address Comorbidities

• Treat anxiety and mood disorders: Improving anxiety may decrease the frequency of CVS episodes and improve inter-episodic symptoms. 1

• Evaluate and treat POTS: This can improve overall functional status and may reduce tachycardia and episode frequency. 1

• Consider migraine prophylaxis: If migraine is a comorbidity, standard migraine preventive strategies may help. 1

Coalescent CVS Warning

A subset of patients with severe CVS experience worsening over years, with increased episode length and frequency, progressively fewer asymptomatic days, and eventual daily nausea and vomiting. 1 These patients lose the prototypical "well periods" between episodes and pose a major diagnostic challenge, potentially meeting criteria for chronic nausea vomiting syndrome rather than CVS. 1