What is..Cannabinoid Hyperemesis Syndrome?, By Dario Sabaghi

Cannabis can treat several pathologies and relieve patients suffering from chronic pain. Moreover, scientific research on cannabis has produced thousands of studies over the years that confirmed the UN’s vote. But as cannabis is going mainstream and the demand for its medical use increases, it’s essential to understand the possible side effects that may occur in the long-term.

Cannabinoid Hyperemesis Syndrome (CHS) is a medical condition related to long-term cannabis use that leads to repeated and severe bouts of vomiting. As this syndrome has not been covered much over the years, studies differ on how many patients show symptoms directly related to CHS.

A study published in the Basic & Clinical Pharmacology & Toxicology1 journal shows that around 32.9% of long-term cannabis users meet the criteria of the definition of CHS. However, this percentage seems bigger than the figures of other studies, which show only 6%-9% of patients suffering from this syndrome.

Besides episodic cyclic vomiting, CHS also involves nausea, treated with conventional antiemetic therapy, that is often accompanied by abdominal pain. Those who suffer from it may also experience sweating, flushing, thirst, weight loss and changes in body temperature. CHS can be under-recognized because its diagnosis may be confused with cyclical vomiting disorder, which is a health problem that causes similar symptoms.

Also, the stigma associated with cannabis use, and the illegal status of cannabis in many countries may lead patients to under-report cannabis use, making CHS diagnosis more difficult. CHS is a newly-discovered pathology. One of the first cases was reported by doctor James Hugh Allen in 20042. However, professor Mitch Earleywine found evidence of similar symptoms in Arab writings from the 11th century3.

The causes4 that bring some regular cannabis users to develop the CHS are not so clear. Some researchers suggest that genetics might play a role. Other researchers think that the effects of cannabis can change with chronic use. Another theory identifies the two receptors of the endocannabinoid system, called CB1 and CB2, as the cause of CHS. Receptors respond to specific stimuli or changes in the environment.

The CB1 receptors are mainly present in the brain, but they are also in other organs. Most CB2 receptors are present on cells of the immune system at high density, including macrophages, mast cells and in the spleen. In the central nervous system, they are primarily located in the spinal cord. In CHS, the receptors that cannabinoids bind to may become altered. Some may turn more active, while others may be deactivated.

These changes may be responsible for the symptoms of CHS. Although these theories lack evidence and require further study, experts agree on regular cannabis use as the first point of responsiblity for CHS.

Most cannabis users don’t suffer from CHS. Although the cannabis compound cannabidiol (CBD) and cannabigerol (CBG) might contribute to CHS, tetrahydrocannabinol (THC) is a necessary component of the syndrome. Using CBD in the absence of THC hasn’t been linked to CHS. People with CHS suffer from repeated bouts of vomiting, but between these episodes, there are no other symptoms. Experts divide these symptoms into three different stages: the prodromal phase, the hyperemetic phase, and the recovery phase.

In the prodromal phase, the main symptoms are often nausea and abdominal pain. In the hyperemetic phase, symptoms may include ongoing nausea and repeated vomiting, as well as abdominal pain, decreased food intake and weight loss and dehydration. During this phase, symptoms are often intense and overwhelming. CHS may continue until the person completely stops using cannabis.

When the recovery phase starts, symptoms disappear. However, they can last days or months, and they may come back if the person uses cannabis again. A study published in the American Journal of Gastroenterology reports two cases of death5 associated with CHS. However, such deaths are not directly related to cannabis use but to complications of CHS.

The majority of researchers agree that the best treatment for CHS is to cease using cannabis. However, a complete absence of cannabis might not be possible for patients that use medical cannabis.  Experts explored many treatment options for symptom resolution and disease management.

The emergency department set intravenous hydration and antiemetics for symptom relief. However, antiemetics are infrequently effective in relieving nausea and vomiting of CHS patients. As a result, alternative therapies are now being used for symptomatic management. For instance, CHS patients turn to hot showers and baths for symptomatic relief before seeking medical care. Thus, hot water should be considered as one of the standard therapies for CHS.

Hot water bathing provides significant relief in many cases and reports indicate that showers/baths are now considered a learned behaviour pattern of CHS, according to a study published in The American Journal of Therapeutics6. As CHS remains a poorly understood complication of regular cannabis users, more research is needed on this syndrome due to the rise of cannabis use around the world.

Doctors and nurses should remain up-to-date on the diagnosis as it can be easily confused with cyclical vomiting disorder. Information and scientific research on CHS should work together to treat a syndrome that can be debilitating for patients that use cannabis for medical purposes and for all other people that use recreational cannabis.