According to a story from LA Weekly, a lot of media coverage concerning cannabis has been largely positive in recent years. The medicinal value of CBD, for instance, has seen increased recognition, with it having gained approval for rare epilepsy disorders such as Dravet syndrome. Furthermore, medicinal and even recreational uses of cannabis come with relatively few negative side effects, at least when compared to other drugs.

However, as with so many other things in life, it’s definitely possible to have too much of a “good thing.” One rare side effect of long-term heavy use of cannabis is a condition called cannabinoid hyperemesis syndrome (CHS).

Cannabinoid hyperemesis syndrome is a condition characterized by frequent vomiting, stomach pain, and nausea. The condition is caused by frequent (at least weekly, if not daily) use of cannabis at a relatively high dose. The method of use does not appear to impact CHS. While heavy cannabis use is the cause, the mechanism behind this is unclear; typically, cannabis use can have antiemetic effects, meaning that it reduces nausea and vomiting. Therefore, the symptoms of CHS are paradoxical.

The symptom trajectory of the condition can be broken down into three phases:

1. Prodromal – This is the first phase of symptoms in which relatively mild nausea, increased thirst, sweating, and anxiety appear. In this phase, cannabis users may increase their use in an attempt to relieve their persistent nausea. This phase can last as long as several months or even years.
2. Hyperemetic – Characteristic symptoms of retching, vomiting, nausea, and abdominal pain begin. These symptoms are remarkably persistent, with retching occurring as frequently as five times an hour. These symptoms are similar to cyclic vomiting syndrome. Patient may develop weight loss and dehydration, as ingesting food or medication during this period is almost impossible. Acute symptoms may last for as long as two days and can recur without warning.
3. Recovery – This phase begins after diagnosis, when the patient halts their cannabis use. Full recovery can take weeks or months. Patients will usually revert to the hyperemetic phase if they use cannabis during recovery, so an accurate diagnosis and patient education is critical.

Traditional approaches for relieving nausea and vomiting are ineffective for cannabinoid hyperemesis syndrome. The only way to completely halt symptoms is cessation of cannabis use. Attempts to begin use again after symptoms have resolved runs the risk of them returning. Mental health support for patients may be necessary to help with cessation of use. Hot showers or baths can also provide temporary relief of acute symptoms. Antipsychotic medications like olanzapine have provided total relief of symptoms in some case reports.

While the condition is still generally rare, particularly considering how widespread cannabis use has become, it’s still nevertheless an adverse effect that regular users of cannabis, either for medical or recreational purposes, should be aware of.