It’s estimated that around 277 million people use cannabis worldwide (Sorensen et al., 2017). That’s about 5% of the whole population (Sorensen et al., 2017)! In 2014, 22.2 million Americans who were 12 years old or older were active cannabis users (that’s a little more than 8% of America’s population at that time) (Sorensen et al., 2017). But what happens when a drug used by so many people has a chance to make them sick. And by sick, I’m not referring to addiction, which is a disease, but rather a sickness like when you get the flu. Specifically, a sickness that makes you constantly vomit! That type of sickness is known as cyclic hyperemesis syndrome (Abell et al., 2008; Allen et al., 2004; Parker, 2017; Sorensen et al., 2017). Cyclic hyperemesis syndrome is when people experience periods of intense vomiting that can last anywhere from hours to days (Abell et al., 2008; Allen et al., 2004). It typically is followed by periods of non-vomiting that can last weeks or months, only to be followed up by the routine vomiting periods, hence the “cyclic” part of its name (Abell et al., 2008; Allen et al., 2004). Cyclic hyperemesis syndrome is something that exists without the presence of cannabis and is it’s own sickness, but there are findings that cannabis might cause something called cannabinoid hyperemesis syndrome which is effectively a type of cyclic hyperemesis syndrome related to cannabis (Abell et al., 2008; Allen et al., 2004; Sorensen et al., 2017). 

So, how do we know cannabis can have anything to do with vomiting? Doesn’t smoking weed just go to your head (literally)? There are many studies that point to how cannabis can act as an antiemetic (stopping vomiting) (Allen et al., 2004; Hu et al., 2007; Parker, 2017; Sorensen et al., 2017). For example, one study looked at how cannabis can help relieve vomiting caused by Staphylococcal enterotoxin (the bacteria that typically gives you food poisoning!) (Hu et al., 2007). Hu et al. (2007) tested to see how activation of cannabinoid receptors (specifically CB-1 receptors) could affect vomiting in shrews. What they found was that CB-1 receptor activation with agonists (like THC in cannabis) reduced vomiting caused by Staphylococcal enterotoxin and that antagonists to those receptors increased vomiting. What these findings show is that there is a link between cannabis and vomiting.

But you may be asking yourself, how would cannabis cause vomiting in cannabinoid hyperemesis syndrome if it usually decreases vomiting? The short answer is we don’t really know how, but we know that it certainly seems to. One theory is that it may have to do with change of the number of CB-1 receptors after chronic cannabis use, but scientists are still unsure (Parker, 2017). The reason we seem to know it’s related, however, is through cases of cannabinoid hyperemesis syndrome. In a study by Allen et al. (2004), they tracked 10 cases of what they thought to be cannabinoid hyperemesis syndrome. In all 10 cases, chronic cannabis use preceded the syndrome and in seven of the cases, stopping cannabis use stopped the cyclic vomiting syndrome. The three other participants who continued to experience cyclic vomiting did not stop using cannabis. Additionally, three of the seven people who did stop using cannabis went back to using cannabis and their vomiting returned. Then, two of those three that returned to cannabis stopped again and their vomiting did too! These findings seem to show that cannabis causes cyclic vomiting in cannabinoid hyperemesis syndrome, since we see those that use cannabis experience cyclic vomiting and as soon as they stop using cannabis, vomiting goes away. And to further  demonstrate cannabis’ role, once they start using again, their vomiting returns! A review paper on cannabinoid hyperemesis syndrome supports these findings noting that ~74% of those with cannabinoid hyperemesis syndrome had been using cannabis for over a year, and that in ~97% of them, symptoms stopped after cannabis cessation (Sorensen et al., 2017)

So, does this mean that if you use cannabis you’re going to start vomiting a lot? No. Almost all cases of cannabinoid hyperemesis syndrome were in chronic users and not all users develop it, only a small percentage (Sorensen et al., 2017). Also, if you’re a woman, you’re in luck! ~73% of people with cannabinoid hyperemesis syndrome were found to be men (Sorensen et al., 2017). Cannabis is a great drug that can do great things for people and shouldn’t be avoided just because of the chance that you could develop cannabinoid hyperemesis syndrome, but it’s important to be aware of the possibility of it and to also know that if you are experiencing sickness while using cannabis, cannabis might be the cause. As always, if you’re sick and not sure what’s going on, go check with your doctor.

Citations:

Abell, T. L., Adams, K. A., Boles, R. G., Bousvaros, A., Chong, S. K. F., Fleisher, D. R., Hasler, W. L., Hyman, P. E., Issenman, R. M., Li, B. U. K., Linder, S. L., Mayer, E. A., Mccallum, R. W., Olden, K., Parkman, H. P., Rudolph, C. D., Taché, Y., Tarbell, S., & Vakil, N. (2008). Cyclic vomiting syndrome in adults. Neurogastroenterology & Motility, 20(4), 269–284. https://doi.org/10.1111/j.1365-2982.2008.01113.x

Allen, J. H., de Moore G M, Heddle R, & Twartz J C. (2004). Cannabinoid hyperemesis: Cyclical hyperemesis in association with chronic cannabis abuse. Gut, 53(11), 1566–1570. https://doi.org/10.1136/gut.2003.036350

Hu, D.-L., Zhu, G., Mori, F., Omoe, K., Okada, M., Wakabayashi, K., Kaneko, S., Shinagawa, K., & Nakane, A. (2007). Staphylococcal enterotoxin induces emesis through increasing serotonin release in intestine and it is downregulated by cannabinoid receptor 1. Cellular Microbiology, 9(9), 2267–2277. https://doi.org/10.1111/j.1462-5822.2007.00957.x

Parker, L. A. (2017). Cannabinoids and the Brain. MIT Press.

Sorensen, C. J., DeSanto, K., Borgelt, L., Phillips, K. T., & Monte, A. A. (2017). Cannabinoid Hyperemesis Syndrome: Diagnosis, Pathophysiology, and Treatment—a Systematic Review. Journal of Medical Toxicology, 13(1), 71–87. https://doi.org/10.1007/s13181-016-0595-z