Cannabis and Nausea: The Controversial Connection

For years, cannabis has been hailed as a miracle medicine for nausea, with cancer patients using it during chemotherapy and everyday users swearing by its stomach-settling powers. But what if cannabis itself could actually cause unrelenting bouts of nausea and vomiting? This idea may have seemed absurd in the past, but doctors have now identified a condition that appears to do just that: cannabinoid hyperemesis syndrome (CHS).

Is CHS Real?

While CHS remains rare, awareness of this condition is increasing among doctors and regulators. The first clear description of CHS appeared in a 2004 case series from Adelaide, Australia. Doctors reported patients who had been long-term, heavy cannabis users experiencing cyclical bouts of nausea, abdominal pain, and vomiting that would only resolve once they stopped using cannabis. What caught their attention was the strange behavior patients developed, taking repeated hot showers for temporary relief. This “compulsive bathing” became one of the syndrome’s clinical hallmarks, although it is not relevant for the current diagnosis of CHS.

For years, skeptics argued that CHS was a coincidence, a misdiagnosis, or the result of contaminated cannabis. However, case after case, across continents, something resembling a cannabis-related syndrome has been documented. In the 2010s, emergency departments in legalization states like Colorado and California began reporting sharp increases in vomiting-related hospital visits that correlated with rising cannabis availability. Large epidemiological studies have also confirmed that heavy, daily use is strongly associated with recurrent vomiting episodes, and that cessation of cannabis use resolves the problem.

Even Vermont’s Department of Health has tracked an increase in CHS-related emergency visits after legalization. In a 2019 systematic review, Dr. Thangam Venkatesan and others analyzed 25 case series and 105 individual reports. They found that while only a minority of cases met rigorous follow-up standards, most patients’ symptoms remitted with abstinence. The authors urged for stricter diagnostic criteria.

The overall picture is clear: CHS is reproducible and cannot be explained away by contamination. However, it may still be a subset of cyclic vomiting syndrome, which is not cannabis-related. In response, the American Gastroenterological Association issued a 2024 clinical practice update formally recognizing CHS as a subtype of cyclic vomiting syndrome and providing diagnostic criteria.

The exact mechanism of CHS remains unclear, but leading theories suggest that chronic high-THC exposure overstimulates CB1 receptors and involves TRPV1 pathways (the same receptors triggered by capsaicin and heat, which explains why hot showers may bring relief). So while CHS may be real, it is still very uncommon. Nonetheless, it has been scientifically sustained in case series, hospital data, and now formal guidelines.

 

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