CHS causes cyclical severe nausea and vomiting in heavy cannabis users through mechanisms that may involve receptor desensitization, TRPV1 activation, and disrupted gut motility.
Heavy daily cannabis users experiencing unexplained cyclical vomiting, or ER doctors who keep seeing it.
What the researchers found
Cannabinoid hyperemesis syndrome is one of the most counterintuitive conditions in medicine: cannabis, widely known for treating nausea, causing severe cyclical vomiting in heavy users. This review examined what was known about why.
The leading theories centered on the biphasic nature of cannabinoids. At low doses, cannabinoids are antiemetic through CB1 receptor activation in the brainstem. But chronic high-dose exposure appears to desensitize these receptors and shift the balance toward pro-emetic pathways. TRPV1 receptors — the same receptors that respond to capsaicin (hot pepper) — emerge as key players, which explains the characteristic symptom of CHS: patients find relief from hot showers and baths, which activate TRPV1 externally.
The review also highlighted that CHS shares features with cyclical vomiting syndrome and anticipatory nausea from chemotherapy, suggesting overlapping brain mechanisms. Standard antiemetics typically don't work for CHS. Anxiolytics, sedatives, hot showers, and ultimately cannabis cessation are the only consistently effective treatments.
Why it matters
CHS is underdiagnosed because most patients — and many doctors — don't connect vomiting with cannabis use. It's the opposite of what both parties expect cannabis to do. This review laid out the biology behind the paradox: the same receptor system that suppresses nausea at one dose can promote vomiting when chronically overstimulated.
The hot shower finding is medically important beyond CHS. It points to TRPV1 as a central player, which opens potential pharmacological targets. And the fact that standard antiemetics don't work means emergency departments need to recognize CHS specifically rather than treating it as generic vomiting.
The numbers in context
• Only permanent cure: complete cannabis cessation
• Hot showers/baths provide temporary relief (TRPV1 mechanism)
• Standard antiemetics: ineffective for CHS
• Effective treatments: anxiolytics, sedatives, hot water, cessation
• Prevalence unknown due to underdiagnosis and symptom overlap
How the study worked
Narrative review of clinical case literature, preclinical cannabinoid pharmacology, and proposed pathophysiological mechanisms for CHS. Published in Cannabis and Cannabinoid Research.
Who was studied
Review of existing literature on cannabinoid hyperemesis syndrome (CHS)
What this study cannot tell us
CHS prevalence remains unknown due to underdiagnosis. Most evidence comes from case reports and case series rather than controlled studies. The proposed mechanisms (receptor desensitization, TRPV1) are plausible but not definitively proven. The review cannot explain why only some heavy users develop CHS while others don't.
How to read the evidence
Narrative review synthesizing case literature and pharmacological theory. Mechanisms are plausible but not confirmed by controlled studies.
When this study was published
Published in 2020. CHS awareness and diagnosis have improved since, and topical capsaicin has been increasingly used as treatment.
The bigger picture
As cannabis potency and use frequency have both increased, CHS has gone from a medical curiosity to a recognized emergency department presentation. Some estimates suggest it affects a meaningful minority of daily heavy users. The condition serves as a concrete example of the dose-dependent paradox that runs through cannabis pharmacology: the same compound can heal or harm depending on dose and duration.
Replication
Not stated in abstract.
Funding
Not reported in abstract.
Conflicts of interest
Not reported in abstract.
Questions still open
- What percentage of daily heavy cannabis users eventually develop CHS?
- Is there a genetic predisposition to CHS?
- Could topical capsaicin cream replace hot showers as a TRPV1-based treatment?
Common questions
Why does cannabis make some people vomit when it's supposed to help nausea?
Why do hot showers help CHS?
Read the original research
Cannabinoid Hyperemesis Syndrome: A Review of Potential Mechanisms.
Cannabis and cannabinoid research, 5(2), 132-144
Cannabis and Cannabinoid Research is a peer-reviewed journal focusing on the science and clinical applications of cannabis.
Citation
DeVuono, Marieka V; Parker, Linda A. (2020). Cannabinoid Hyperemesis Syndrome: A Review of Potential Mechanisms.. Cannabis and cannabinoid research, 5(2), 132-144. https://doi.org/10.1089/can.2019.0059