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

The takeaway

An updated review of cannabis hyperemesis syndrome describes it as a functional gut-brain axis disorder driven by the endocannabinoid system, with increasing cases and limited effective treatments beyond cannabis cessation.

Emergency physicians, gastroenterologists, and chronic cannabis users experiencing cyclical vomiting.

Cannabis is anti-emetic at low doses but pro-emetic at higher doses

What the researchers found

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.

Why it matters

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.

The numbers in context

First described in 2004; increasing cases worldwide; cannabis biphasic effect: anti-emetic at low doses, pro-emetic at higher doses; capsaicin and haloperidol show benefit in case reports.

How the study worked

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

What this study cannot tell us

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

How to read the evidence

Moderate: comprehensive narrative review with mechanistic detail, though not systematic and limited by case-report-level treatment evidence.

When this study was published

Published 2020.

The bigger picture

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.

Questions still open

Why do only some chronic cannabis users develop CHS? Could genetic variation in CB1 receptors explain susceptibility? Would gradual dose reduction prevent CHS in at-risk users?

Common questions

What is cannabis hyperemesis syndrome?

A condition in chronic cannabis users characterized by episodes of severe nausea and vomiting, often relieved by hot baths or showers. It results from changes in how the endocannabinoid system processes cannabinoids after prolonged heavy use.

Why does cannabis cause vomiting if it is supposed to prevent nausea?

Cannabis has a biphasic effect: anti-emetic at low doses but pro-emetic at higher doses. In chronic users, CB1 receptor downregulation and desensitization may shift the balance toward the pro-emetic effect.

Read the original research

Cannabis hyperemesis syndrome: an update on the pathophysiology and management.

Annals of gastroenterology, 33(6), 571-578

View on PubMed ↗Publisher’s paper ↗

Citation

Perisetti, Abhilash; Gajendran, Mahesh; Dasari, Chandra Shekhar; Bansal, Pardeep; Aziz, Muhammad; Inamdar, Sumant; Tharian, Benjamin; Goyal, Hemant. (2020). Cannabis hyperemesis syndrome: an update on the pathophysiology and management.. Annals of gastroenterology, 33(6), 571-578. https://doi.org/10.20524/aog.2020.0528