Cannabinoid Hyperemesis Syndrome: Paradoxical Effects of THC?

There’s one way to die from cannabis, it's called cannabinoid hyperemesis syndrome (CHS). According to the Official Journal of the American College of Gastroenterology, there have been about 2217 reported deaths from CHS. The figure is probably higher considering that most cases are never diagnosed and hence never reported. CHS is a rather new diagnosis that is often confused with cyclic vomiting syndrome (CVS). Both conditions are characterized by cyclic episodes of excessive vomiting (hyperemesis) that may eventually lead to death. Even though exact mechanisms are yet to be confirmed, THC (the psychoactive cannabinoid) has been implicated in CHS. On the flip side, one of the approved uses of THC is in the treatment of chemotherapy-induced nausea and vomiting (CINV). Isn't it paradoxical that THC would both trigger CHS and be an effective cure for CINV nonetheless? 

CHS was first described in a 2004 paper by Allen and colleagues  as cyclical hyperemesis (vomiting) as a result of chronic cannabis abuse. Apart from the vomiting, the researchers also noted that the patients were taking frequent hot baths for relief, as a learned behavior. It is hypothesized that CHS may be as a result of overstimulation of endocannabinoid receptors. Genetics may also have a role to play in the development of CHS, according to preliminary research.

CHS is often divided into three phases. The first is the prodromal phase where the patient experiences early morning nausea and slight abdominal discomfort. This  phase may last for several years. The second is the hyperemetic phase that's characterized by severe nausea and vomiting, abdominal pain and the learned behavior of taking hot baths. Left untreated, the patient can deteriorate quite fast during this stage due to electrolyte imbalance and dehydration. The next stage is the recovery phase.

Most of the patients who’ve been diagnosed with CHS are young adults with a history of chronic cannabis use (16 years on average). They reported daily use of cannabis, up to three or five times per day. Chronic cannabis use is what differentiates CHS from cyclic vomiting syndrome. In addition, the behavior of taking compulsive hot showers is only observed in CHS. 

Treatment for CHS revolves around treating nausea and vomiting and preventing a relapse during the recovery phase. Even with the proven anti-emetic properties of cannabis, this is one case where offering it as a form of treatment may cause more harm than good.