Suspected cannabinoid hyperemesis syndrome ED visits nearly tripled in Northern California over 11 years

Using a narrow CHS definition, annual prevalence increased by 175% from 2009 to 2019 (prevalence ratio=2.75). A broader definition showed a 134% increase (PR=2.34). ED visit rates also increased substantially (rate ratio=2.35 for the narrow definition). Over 57,000 patients had at least one CHS visit under the narrow definition.

Retrospective observational cohort using Kaiser Permanente Northern California electronic health records (2009-2019). Two CHS case definitions applied: a narrow definition based on prior studies and a broader exploratory definition. Both required a primary vomiting diagnosis. Log-link Poisson models estimated trends.

This is one of the largest CHS prevalence studies ever conducted, using a defined health system population rather than emergency department surveillance. The near-tripling of cases over a decade tracks with increasing cannabis availability and potency in California.

CHS was considered rare when first described. This study from a large health system shows it has become a common ED diagnosis, adding urgency to the need for effective treatments and prevention strategies, particularly public education about the condition.

ICD coding may misclassify some cases. Broader definition may capture non-CHS vomiting. CHS awareness among clinicians increased over the study period, potentially inflating diagnosis rates (detection bias). Kaiser members may not represent the general population.