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Cannabinoid hyperemesis syndrome: a remote hypothetical threat, or all-too-real and personal?

 •  • by Paul Ingraham
Weekly nuggets of pain science news and insight, usually 100-300 words, with the occasional longer post. The blog is the “director’s commentary” on the core content of a library of major articles and books about common painful problems and popular treatments. See the blog archives or updates for the whole site.

I recently announced a new article about cannabis for pain. New pages often get updated quickly as reactions pour in and I try to tie up loose ends and wind up dangling from them. But this one? The mother of all loose ends!

When doing my homework for the original version of the article, I learned about cannabinoid hyperemesis syndrome (CHS) and included a horrified token paragraph about it.

And then, the next day, a friend went to the hospital with constant vomiting. I know that he’s a chronic THC user, likely substantial daily dosages for years. I connected the dots and thought, “Hmm, what are the odds? Does he know about CHS?”

The odds were good. His symptoms are classic for severe CHS, the diagnosis is mainly by elimination, and no other cause has been identified. He is over a week into his ordeal, and has been back to the hospital to treat dehydration. He has lost about 16 pounds… so far.

It’s hard to imagine such suffering.

I returned to the topic for a closer look, and now my article has been updated with much more info about puke-your-guts-out-for-days-at-a-time syndrome. Which is beyond awful, and wish I could un-know. My sympathies are with my friend, but this also has implications for me as well — as it probably should for all cannabis users.

This is an abridged version of the new section. If you’re keen to know more, switch to the cannabis page and read the full version.

Cannabinoid hyperemesis syndrome is all-too real and not nearly rare enough

One of the most alarming side effects of THC/CBD is cannabinoid hyperemesis syndrome (CHS): escalating episodes of chills, nausea, and painful projectile vomiting. CHS is usually worse in the morning, and patients often alternate between vomiting and self-treating the chills with hot baths and showers.

How bad is CHS? Episodes tend to recur with increasing frequency and ferocity over time, and it can get so extreme that dehydration is a serious threat, even lethal — like in the case of Brian Denny, who died that way in 2019, a tragic story told by his mother. Even when it’s not deadly, this condition wrecks lives. Even mild nausea is a hard symptom to live with.

Is CHS rare? It’s not “common,” but probably “rare” isn’t really the right word either. Many emergency room docs and nurses are familiar with it. Support groups have been multiplying. It’s hard to connect the dots. And syndromes like this are often the tip of a pathological iceberg. For each severe case, there are probably many minor ones (a disturbing possibility). And it also probably isn’t limited to hardcore usage (though most patients probably were using a lot). While CHS isn’t common, its alleged rarity is probably wishful thinking — the evidence points the other way.

Is this fear-mongering? If only! But CHS is all-too real. Many cannabis fans deny the existence of CHS, and resistance to the diagnosis can be fierce: some people really don’t want to hear a “discouraging word” about cannabis. It’s easy to make a simplistic case against it because cannabinoids are often used for their anti-emetic properties. has lots of well-presented information about CHS, and is a good place to start if you want more information.

The tip of an iceberg

What if a cannabis user just felt mysteriously gross for days at a time, never actually puking but often wanting to? What if she could barely look at food? Woke up every day wondering if it was going to be a bad morning? What if she lost 4 pounds in one episode, then 10 pounds, then 6? What if she had abdominal pain that was “just” a smoldering campfire for days at a time? What if she didn’t live in the shower like so many classic CHS sufferers, but still shivered under the blankets at 4 AM even on hot nights, miserably wondering what the hell could possibly be wrong with her?

And what if every other non-exotic cause was eliminated? Every test was negative?

Could she have a mild version of cannabinoid hyperemesis syndrome? Cannabis nausea syndrome?

I don’t know that CHS actually has mild and atypical forms, but I do know this much: if it does, it’s next to impossible to diagnose. And it would make life grim and miserable even without the drama of projectile vomiting and rehydration nights at the hospital.

Yet another health theory

I just described the last year of my life. As all my regular readers know, I have had a lot of weird health problems since 2015. But my six years of chronic pain and malaise took a distinctive turn for the worse last April. I lost about 12 pounds.

It did not seem like an escalation of my usual bullshit. It seemed like a nasty new thing. Although I never threw up, I was living on the edge of it. I have never been so sick, and it was unlike anything I had ever experienced.

There have been three more similar episodes since then (though less severe, thank gawd). I am at the tail end of the fourth right now. CHS doesn’t seem “likely,” but it seems plausible:

It’s just a theory, and there are several other possible explanations for my troubles, but this mild CHS hypothesis has the great advantage of being easy and harmless to test. Quitting cannabis is the cure, and trying doesn’t cost me much (a valuable sleep aid, but not my only sleep aid). I will stop using THC right now and we’ll see if my episodes stop.

CHS is a pot deal-breaker in any case

Even if nothing I’ve experienced so far has anything to do with CHS, I also have zero tolerance for the risk of tangling with it in the future. For years I have been under the impression that THC is almost perfectly harmless. That belief has now been shattered. That doesn’t mean I think it’s reckless for people to use it in moderation, far from it.

But we must all do our own risk math. And I have had enough medical weirdness for three lifetimes already. Any risk of compounding my troubles with CHS is a deal-breaker for this guy. I will live without cannabis.

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