Cannabis hyperemesis syndrome: the rare case of a valid diagnosis plus hypersensitization hypothesis for development and chronification of this severe somatic cannabis use disorder.

Cannabis hyperemesis syndrome (CHS) is a serious physical consequence of long-term, high-dose cannabis use, and a regional increase in incidence appears to be an indicator of an increase in cannabis use there. In addition to gradually increasing nausea, which escalates into cyclical vomiting attacks, and resistance to classic antiemetics, relief by hot showers is one of the diagnostic criteria. However, the same symptoms are also found in cyclic vomiting syndrome (CVS), which in turn can also be associated with cannabis use, but unlike CHS, cannabis is not causal for CVS. The only diagnostic criterion that can distinguish CHS from CVS is the persistent disappearance of nausea/hyperemesis during cannabis abstinence. Observation periods of 12 months are diagnostically reliable. Most CHS cases described in the literature have a significantly shorter observation period and can therefore only be considered as suspected CHS cases. Since diagnostically safe (i.e. verified by long periods of abstinence) CHS cases have rarely been documented, this case report of an adult cannabis user should be added. Even after 3 weeks of abstinence, blood cannabinoid-levels (tetrahydrocannabinol and tetrahydrocannabinol-carboxylic acid) were relevantly elevated, indicating previous prolonged and higher dose cannabis use. Remarkably, each CHS episode was stronger than the previous one, indicating ongoing sensitization, even in cannabis relapse after prolonged abstinence. The pathophysiology of CHS is still largely unclear. This case history and other previously observed cases provided the impetus for the hypersensitization hypothesis of CHS development and maintenance presented here, which also takes into account the recently published reports of possible relief of severe nausea and vomiting by haloperidol (or droperidol) or by topical capsaicin.