Cannabis hyperemesis syndrome is a growing gut-brain disorder with limited treatment options

CHS is characterized by cyclic nausea and vomiting worsened by cannabis, with compulsive hot bathing/showers for relief. The endocannabinoid system (ECS) plays a central role: cannabis has a biphasic effect (anti-emetic at low doses, pro-emetic at higher doses). Desensitization and downregulation of CB1 receptors in chronic users may shift the balance toward pro-emetic effects. Traditional antiemetics are often ineffective; capsaicin cream (activating TRPV1 receptors) and haloperidol show some benefit.

Narrative review elaborating on the pathophysiology of the endocannabinoid system in CHS, clinical management, and current knowledge gaps.

As cannabis use increases with legalization, CHS presentations to emergency departments are rising. Understanding the ECS mechanisms helps explain why standard antiemetics fail and guides development of targeted treatments.

CHS is paradoxical: a substance famous for treating nausea causes severe vomiting in chronic users. The biphasic dose-response and CB1 receptor downregulation explain this paradox and highlight the danger of assuming "more is better" with cannabis.

Narrative review (not systematic); no formal diagnostic criteria for CHS exist; most treatment evidence from case reports; pathophysiology partly theoretical; prevalence data limited.