When I was a budding new cannabis activist, it was difficult for me to acknowledge any potential downside to cannabis use. As the medical cannabis industry in Arizona was beginning to take shape, I was in my early twenties volunteering at the co-op, attending events, and soaking up information like the young sponge I was. I learned about the historical and pharmaceutical history of cannabis, and the subsequent fear mongering and outlawing of what I thought of as everyone’s favorite plant. The turning tides were exciting, but I’ve never been one for peer pressure, so even as I had essentially turned into a chimney, I did my best to keep an attitude of “it may not be for everyone”. Sure, sometimes I fantasize about every single person in the world knowing the exact strain, dosage, cannabinoid mix and consumption method that works best for them, but that’s just not the reality we live in. Currently, we live in a reality where we still have a ton to learn about cannabis, not just the potential benefits but also the potential risks.
One of the potential risks, and a subject of debate among the medical and cannabis communities, is cannabinoid hyperemesis syndrome, or CHS. Abdominal pain, nausea and cyclical vomiting experienced by ‘chronic cannabis users’ is another to add to our list of things we don’t quite fully understand yet, and that some people think is a myth. Once again we are delving into the murky waters of cannabis science and how little we still understand about all of the ways it might interact with our bodies, but knowledge is power so let’s see what kind of knowledge we can get about a phenomena that some say is on the rise.
What is Cannabinoid Hyperemesis Syndrome
As the name suggests, cannabinoid hyperemesis syndrome (CHS) is hyperemesis - severe or prolonged vomiting - caused by cannabis use, though cannabinoid hyperemesis syndrome is a fairly new term. Often credited to a 2004 study out of South Australia that identified 19 South Australian patients who had a history of what they referred to as “chronic cannabis abuse” in conjunction with a “cyclical vomiting illness”. While a 2004 study may seem a tad outdated, the diagnostic criteria and conclusion formed in this study appears to be the same criteria cited in more modern descriptions of CHS, and gives us about as much information on the phenomenon as we have available today.
The first piece of the diagnostic puzzle that is CHS is the patient's history with cannabis. Patients are often described as having a history of “prolonged, excessive cannabis use” for years prior to the onset of CHS symptoms. As is common for these kinds of cannabis studies, there is no real baseline that I could find for what is considered “prolonged” or “excessive”. Using myself as an example, I have been an almost daily cannabis flower smoker for years, not to mention the edibles, dabs, vapes and other consumables I’ve, well, consumed throughout those years. Would I be amongst those they consider an excessive user? Is there consideration made for those of us who use cannabis daily the way many use prescriptions? As far as I could tell, those specifics are unclear.
Despite the lack of specific information on what might qualify someone as an “excessive” cannabis user in relation to a CHS diagnosis, it seems reasonable to deduce that daily use over several years is the general consensus.
Cyclical Vomiting Episodes
This may not be the first time you’ve heard about cannabis and hyperemesis in the same sentence before, as cannabis is often used as a tool to help ease nausea and vomiting from chemotherapy or in cases of hyperemesis gravidarum - extreme and persistent nausea and vomiting during pregnancy. Cannabis has often been touted as an effective antiemetic. However, in suspected cases of CHS, patients are experiencing a pattern of “hyperemesis every few weeks or months” while they are still actively consuming cannabis. It’s noted in some sources that patients continue using cannabis during episodes in an effort to ease symptoms but are unaware that it may be exacerbating them.
Aside from CHS, there is something called cyclical vomiting syndrome, which the Mayo Clinic describes as “episodes of severe vomiting that have no apparent cause”. Episodes can occur every few days, weeks or months, last hours or days, and often have periods of symptom-free time between occurrences. The Mayo Clinic website lists possible causes as anything from physical exhaustion to allergies or sinus problems. From what I can gather, cyclical vomiting syndrome is distinct from CHS, though “excessive” cannabis use is listed as a possible risk factor.
Very rarely do I write one of these pieces where I get to present you with a cure but today we have one! The cure for cannabinoid hyperemesis syndrome is quitting cannabis. No, really, it does appear to be that simple. According to the 2004 study, “cessation of cannabis abuse led to cessation of the cyclical vomiting illness in seven patients” and that three of the patients that continued to use cannabis also continued to experience cyclical vomiting episodes. A few patients in that study attempted to use cannabis again and their symptoms returned. A study on CHS last updated earlier this year explains that the “only definitive treatment of cannabis hyperemesis syndrome is the removal of cannabis exposure, which may ultimately require extensive coordination between the committed patient, an empathic and dedicated primary care physician, and appropriate substance use counseling and resources”.
So, What Do We Know?
There’s still much to learn about the cause, or causes, of cannabinoid hyperemesis syndrome, but unsurprisingly there are a number of theories as to what the etiology of CHS might be. First and foremost, we know that the endocannabinoid system has receptors all throughout our bodies, on both neurologic and endocrinologic pathways which “informs its unique ability to be both pro- and anti-emetic”. That being said, it’s theorized that one cause of CHS may be “chronic overstimulation of endocannabinoid receptors, leading to derangements in the body’s intrinsic control of nausea and vomiting”. The 2004 study theorizes that, as cannabinoids are lipophilic and “bind to cerebral fat”, a toxic level of cannabinoid “build up” may be affecting sensitive patients and causing the cyclical vomiting episodes.
Besides the unintentional dysregulation of our endocannabinoid system, another theorized cause of CHS is increased levels of THC that are readily available in regulated markets. There is anecdotal evidence to suggest that people who dab may be more likely to develop CHS, and that higher levels of THC available in products, combined with lower concentrations of CBD and other cannabinoids, may contribute to cases of CHS. The 2023 study suggests that the trend of increased levels of THC and decreased CBD “correlates with increased cannabis use” and that some patients reported consuming up to 2000 mg of THC per day.
But the theories don’t stop there. One interesting theory is that Hop Latent Viroid (HLVd) may be the culprit behind CHS. According to one source, a study reported the 90% of California cannabis crops are infected with HLVd and that another study had found 40% of Canadian dispensary flower was infected with HLVd, though they also mention that it is not harmful to humans. Despite this articles assertion, I found a conflicting piece on the National Library of Medicine’s website suggesting that the writer noticed the first cases of HLVd in California’s cannabis crops in 2004, the same year as a noted uptick in cases of CHS, and that failure to eradicate this plant disease may still be a contributing factor.
The Wrap Up
Let’s try to summarize what we know real quick, cause this one was a little all over the place, even for me. Cannabinoid hyperemesis syndrome occurs in people with a history of regular (often referred to as excessive) cannabis use for usually years, before the onset of the illness. Symptoms include nausea, abdominal pain, and bouts of severe or prolonged vomiting that can last for hours or days. These episodes of hyperemesis usually have periods of symptom free periods between episodes. Some episodes may be severe enough that medical intervention is necessary to avoid dehydration and malnutrition. Episodes also occur while the patient is still actively using cannabis and symptoms stop with the cessation of cannabis use, with symptoms returning with resumed use. Causes of CHS are as of yet unknown, but theories abound and are quite varied.
One researcher described the topic of CHS research as a “backwater data area”, which is a lot when you consider how much we still have to learn about cannabis as a whole, but I think there are a few important things I want to note here at the end.
First, part of my cannabis advocacy has to be understanding the possible risks of cannabis use. It’s always been easy for me to be aware and informed about obvious fear mongering or misinformation, but I also want to make an effort to understand the potential risks that are still being worked out in science and hypotheses.
That brings me to my second point, which is that although it’s October, my favorite time of the year, my intention is never to scare anyone. I’ve been seeing an increase in anecdotal reports of CHS on my social media feeds and decided to do a deeper dive into the subject. In my opinion, having all of the information is often a good thing, even if I don’t necessarily like or know what to do with that information initially. In this case, I have every intention of keeping an ear to the ground for more information or scientific developments when it comes to CHS, although I’m not convinced after the last 20 years of stagnation on the subject. One researcher called this a “backwater data area” of cannabis science, which even as a layman, says a lot.