Nice, eh? And yes, it goes completely against the grain of what we think we know about marijuana: Ironically, cannabis is frequently employed to prevent the nausea and vomiting frequently associated with chemotherapy.
So what gives? The answer is that, so far, nobody really knows.
First things first: It appears to be a very rare side effect of regular marijuana use, and it was not documented in the medical literature until 2004. Given the long history of pot-smoking the world over, it is reasonable to ask where the cannabis emesis syndrome has been hiding all these years. A fair question, but one which, at this stage, has no satisfying answer.
Cannabinoid hyperemesis, as it's known, was first brought to wider attention earlier this year by the anonymous biomedical researcher who calls himself Drugmonkey. Posting on his eponymous blog, Drugmonkey documented cases of hyperemesis that had been reported in Australia and New Zealand, as well as Omaha and Boston in the U.S.
"There were two striking similarities across all these cases," Drugmonkey reported. "The first is that patients had discovered on their own that taking a hot bath or shower alleviated their symptoms. So afflicted individuals were taking multiple hot showers or baths per day to obtain symptom relief. The second similarity is, as you will have guessed, they were all cannabis users."
Heavy, regular cannabis users, most of them. And hot baths? Where did THAT come from?
More evidence was not long in coming. In February, researchers in the Division of Gastroenterology at William Beaumont Hospital in Royal Oak, Michigan, identified eight patients in their gastroenterology wards who were suffering from "otherwise unexplained refractory, recurrent vomiting." As the researchers reported in the journal Digestive Diseases and Sciences , there were two other significant features the eight patients shared: They were all chronic cannabis smokers--and they were all compulsive bathers.
The connection between uncontrolled vomiting and heavy toking seemed unequivocal: "Four out of five patients who discontinued cannabis use recovered from the syndrome," according to the published report, "while the other three patients who continued cannabis use, despite recommendations for cessation, continued to have this syndrome."
There is precious little anecdotal evidence to support this surprising finding. Occasionally, naive marijuana smokers will ingest too much and become sick to their stomach. And it is possible to incur the (brief) wrath of cyclic vomiting by eating way too many marijuana brownies, or other cannabis foodstuffs. Short of that, I am not familiar with vomiting as a documented side effect of regular cannabis use, and I venture to guess that most readers aren't, either.
However, the reports haven't stopped. This summer, an intriguing account appeared in Clinical Correlations , the official blog of New York University's Division of General Internal Medicine. Sarah A. Buckley and Nicholas M. Mark, 4th year medical students at the NYU School of Medicine, speculated on the cannabis hyperemesis phenomenon, and offered a formal definition: "A clinical syndrome characterized by intractable vomiting and abdominal pain associated with the unusual learned behavior of compulsive hot water bathing, occurring in the setting of long-term heavy marijuana use."
After reviewing 16 published papers on the syndrome, Buckley and Mark asked the obvious question: "How can marijuana, which is used in cancer clinics as an anti-emetic, cause intractable vomiting? And why would symptoms abate in response to high temperature?"
One possible mechanism involves marijuana's penchant for fats. Theoretically, this "lipophilicity" could cause increasingly toxic concentrations of THC over time, in susceptible people. "The abdominal pain and vomiting are explained by the effect of cannabinoids on CB-1 receptors in the intestinal nerve plexus," they write, "causing relaxation of the lower esophageal sphincter and inhibition of gastrointestinal motility." The authors speculate that low doses of THC might be anti-emetic, whereas in certain people, the high concentrations produced by long-term use could have the opposite effect.
As for the hot baths, Buckley and Mark note that "cannabis disrupts autonomic and thermoregulatory functions of the hippocampal-hypothalamic-pituitary system," which is loaded with CB-1 receptors. The researchers conclude, however, that the link between marijuana and thermoregulation "does not provide a causal relationship" for what they refer to as "this bizarre learned behavior."
These questions, like many questions having to do with regular marijuana use, are not likely to be answered definitively anytime soon, for a number of good reasons, some of which are delineated by the authors:
--"The legal status of marijuana makes eliciting an accurate drug history challenging."
--"The bizarre hot water bathing is likely often attributed to psychological conditions such as obsessive-compulsive behavior."
--"The knowledge of the anti-emetic effects of cannabis likely disguise cases of cannabinoid hyperemesis, leading to the erroneous belief that cannabis is treating cyclic vomiting rather than causing it."
--"The fact that this syndrome is so recently described and relatively unknown outside an esoteric subset of the GI [gastrointestinal] literature means that most clinicians are unaware of its existence."
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