Dear Editor,

I read with great interest the systematic review by Senderovich et al. [1] on cannabis hyperemesis syndrome (CHS) and its treatment. This systematic review was well-conducted; however, some general concerns on the validity/rigor of diagnoses of CHS should be considered. Were the symptoms of the included samples really based upon CHS itself? In this context, it should be outlined that only the ROME-IV criterion “complete CHS-remission alongside sustained cannabis cessation” [2] can be considered to be a pathognomonic CHS-sign [3, 4, 5]. All other signs (including prolonged cannabis use, stereotypical episodes of nausea/vomiting, prodromal abdominal pain as well as pathological hot bathing/showering behavior) are shared by CHS with the cyclic vomiting syndrome (CVS), supporting the common view that CHS is a subset of CVS [2, 4]. As a rule, a rigorous differentiation between these two conditions has failed due to a paucity of published studies lasting longer than a few days or weeks of cannabis abstinence to reliably exclude a breakthrough of episodic vomiting/emesis as a prerequisite for clearly distinguishing CHS from CVS [4]. The same applies to the samples/cases evaluated in the review of Senderovich et al. [1].

At this juncture, it remains to be clarified, how long an abstinence period should last to be reasonably sure that the condition is indeed CHS and not CVS. Certainly, the longer the better. There are only 2 case reports in the literature demonstrating a symptom-free period longer than 5 years after stopping long-term cannabis use, thereby strongly supporting the concept of CHS as disease entity, i.e., as a specific cannabis use disorder [5]. Taking into account that the ROME-IV Chapter Committee previously has not defined a minimum duration of cannabis abstinence required for diagnosing with CHS [2], there is now some evidence that a period of approximately 12 months of complete symptom resolution after cessation of long-term cannabis use should be appropriate to definitely distinguish between CHS and CVS [3]. All other cases should be regarded as “suspected CHS” or simply, as cannabis-related cyclic/episodic hyperemesis conditions, covering both, CHS and CVS. Of course, the differentiation between CVS and CHS is simple in patients without regular cannabis use [4].

CHS prevalence is expected to rise along with the increasing cannabis use and potency in the shadow of cannabis liberalization and legalization trends [6]. In this regard, the prevalence of CVS in Colorado, USA, has nearly doubled since the liberalization of medical marijuana in 2009, suggesting a broad overlap of CHS and CVS [7]. Vice versa, the samples included in this review were likely to be not representative for CHS populations alone as a “contamination” with a good portion of CVS cases could not be excluded considering the lack of attention given to the duration of symptom-free periods post-cessation [1]. This concern can be extended to most studies and case reports which have dealt with CHS.