Last updated : May 12, 2025
Doctors throughout Denver are warning of a significant increase in a mysterious illness linked to frequent marijuana use. The condition is called Cannabinoid Hyperemesis Syndrome (CHS) and doctors say the number of patients contracting this little-known condition has doubled since marijuana was legalized in Colorado. Here’s what researchers have discovered about CHS so far.
Marijuana typically functions as an anti-emetic, meaning it reduces feelings of nausea. This is one of the biggest arguments for the legalization of marijuana for medical use, because the drug could reduce the nausea associated with chemotherapy in cancer patients. It often works better for this purpose than many pharmaceutical drugs. But for some reason, chronic marijuana use triggers a paradoxical effect in certain patients: A constant feeling of nausea that lasts for days (hyperemesis) accompanied by frequent bouts of vomiting.
These are the main symptoms of CHS. Researchers with the National Institutes of Health, who first helped identify CHS as a clinical condition in 2004, report that patients can vomit as much as five times per hour. It frequently involves severe stomach pain. The condition commonly leads to hospitalization and an IV drip to rehydrate. The NIH reports that patients can often lose 5 pounds of water weight during a bout with CHS. Thinking that marijuana will reduce the feelings of nausea, patients with CHS will often smoke more marijuana than usual, not realizing that it was the trigger for the condition. Doctors can also misdiagnose CHS, thinking that it is a similar condition known as Cyclic Vomiting Syndrome.
These symptoms are sometimes an employers first clue that an employee may be using drugs, and would, in conjunction with other signs, be a legitimate reason to conduct reasonable suspicion drug testing.
Researchers have found that CHS primarily occurs in males. Other risk factors include being separated, divorced or widowed. Doctors don’t know if this is because single men are more likely to use marijuana, or if there is a psychological component tied to ending a relationship that contributes to the condition. They say more research is needed.
The only patients who do develop CHS tend to be those who use marijuana frequently—two to five times daily—for a period of years. The most common sufferers have been heavy marijuana users who have done so for more than a decade, although a few cases have been discovered in which CHS developed in as little as three years.
People suffering from a bout of CHS often discover on their own that taking a hot bath or shower is the only thing that will temporarily relieve the symptoms of vomiting and nausea. Taking a hot bath can ease the symptoms for about 15 minutes at a time, so they’ll take frequent baths.
The hyper-emetic phase will usually go away on its own after 48 hours. Doctors will prescribe fluid resuscitation and anti-emetic medications to help keep the nausea at bay. Patients can usually go back to a regular bathing schedule at that point as well. However, according to doctors at the University of Colorado Hospital who have been studying the condition, this can go on for months at a time. The symptoms of one bout will clear up, the patient goes home and resumes smoking marijuana, and then they end up back in the emergency room hooked up to an IV.
So, what triggers CHS in chronic marijuana users? Doctors still don’t know. Humans have cannabinoid receptors in the brain and in the gastrointestinal system. With the small amount of research that’s been done on CHS so far, doctors still aren’t sure what exact cause of the condition is. For some reason, it impacts a small number of frequent marijuana users when it triggers that paradoxical symptom of constant nausea and frequent vomiting.
Researchers with the University of Colorado Hospital have been tracking emergency room visits for CHS. During the 2008-2009 period, 41 patients checked into the emergency room while suffering from the condition. The number jumped up to 87 visits, more than doubling, during the 2010-2011 period of “post-liberalization” for medical marijuana. Many patients suffer with the condition and never go to the hospital. Doctors will sometimes have difficulty diagnosing CHS because a lot of patients are still nervous about letting their doctor know of their marijuana use. Doctors across Colorado now say they’re seeing cases of CHS on a weekly or even daily basis.
The only certain method of making sure that CHS symptoms go away and don’t come back is to completely stop using marijuana. Once a person begins suffering from CHS, they can relieve the symptoms by no longer smoking marijuana. But as soon as they start using it again, the symptoms automatically come back.
