Please use this link to access this publication. Abstract Background As access to cannabis has increased, there has been a rise in a condition called cannabinoid hyperemesis syndrome (CHS). This study estimates annual prevalence of suspected CHS at emergency department visits (ED) over an 11-year period in Northern California. Methods This retrospective observational cohort study used electronic health records from Kaiser Permanente Northern California. Two CHS case definitions were used to construct two cohorts of adults (18+) with ≥1 CHS visits from 2009 to 2019. The primary definition used a narrow definition based on past studies (CHS group 1) and an exploratory definition allowed...