Cannabis Hyperemesis Syndrome May Depend on More Than Cannabis Exposure Alone
A 2019 study published in the Canadian Journal of Emergency Medicine found that people with cannabis hyperemesis syndrome (CHS) did not have substantially higher long-term cannabinoid exposure than other frequent cannabis users. The finding challenges the idea that CHS is simply the predictable result of consuming the largest amounts of cannabis.
CHS is associated with recurring episodes of severe nausea, vomiting, and abdominal pain in people who use cannabis regularly. Some patients also report temporary relief from hot showers or baths. Repeated vomiting can cause dehydration, electrolyte abnormalities, and acute kidney injury, making emergency evaluation important when symptoms are severe or persistent.
What the study examined
Researchers from Queen’s University and the Hospital for Sick Children analyzed hair and urine samples from emergency-department patients. The study included adults who had experienced at least two episodes of severe vomiting during the previous year and had used cannabis at least three days a week for six months or longer.
The researchers compared patients meeting those criteria for suspected CHS with two control groups: frequent cannabis users without a history of hyperemesis and emergency-department patients being treated for unrelated conditions. People using synthetic cannabinoids, chronic opioids, or acutely misusing alcohol were excluded.
Hair samples were tested for several cannabinoids, including delta-9-tetrahydrocannabinol (THC), cannabinol (CBN), cannabidiol (CBD), and the THC metabolite 11-nor-9-carboxy-THC. Hair testing was used to estimate exposure over a longer period than a single urine test can provide.
Exposure levels overlapped
THC and CBN concentrations in hair showed considerable overlap among the CHS and control groups. After adjustment for age and sex, the differences in cannabinoid concentrations were small and not statistically significant. CBD and THC-COOH were frequently below the laboratory’s limit of quantification.
The researchers did observe a lower THC-to-CBN ratio among CHS patients compared with the recreational-user control group, largely because CBN concentrations were higher in the CHS group. That difference was not seen when CHS patients were compared with the emergency-department controls.
Overall, the results suggest that heavy cannabis use may be necessary for CHS in many patients but is not sufficient by itself to explain who develops the syndrome. The study was small, and its observational design cannot establish what causes CHS. Its findings instead point to the possibility that individual susceptibility, product characteristics, metabolism, or other unidentified triggers may influence risk.
Treatment remains centered on stopping cannabis
Because the underlying mechanism remains uncertain, there is no universally established medication that prevents CHS. The most consistently supported long-term approach is sustained cannabis cessation. Patients who have difficulty stopping may benefit from medical follow-up and support for cannabis use disorder; the Canadian Centre on Substance Use and Addiction’s briefing on CHS discusses barriers to quitting and the need for ongoing support.
During an acute episode, clinicians may provide intravenous fluids, correct electrolyte abnormalities, and use medications for nausea or vomiting. Topical capsaicin and dopamine-blocking medicines such as haloperidol or droperidol are sometimes used in emergency care, but the evidence remains limited and mixed. A 2024 systematic review from the Society for Academic Emergency Medicine found potentially beneficial evidence for dopamine antagonists and mixed evidence for capsaicin, while emphasizing the need for better clinical trials. Earlier reviews likewise concluded that cannabis cessation is the most effective established treatment.
The Queen’s University study does not show that cannabis exposure is unrelated to CHS. Instead, it indicates that cannabinoid levels alone may not explain why some frequent users develop repeated vomiting while others do not. More research is needed to identify the biological and behavioral factors that determine susceptibility and to improve treatment for patients who experience this debilitating condition.
