A condition long hidden beneath vague diagnostic codes is finally surfacing in emergency data — and its true burden may be substantially larger than clinicians previously recognized. Cannabis hyperemesis syndrome (CHS), marked by cyclical, debilitating nausea and vomiting in heavy cannabis users, has historically been miscoded or missed entirely, making population-level tracking nearly impossible.
Analyzing CDC National Syndromic Surveillance Program data spanning January 2023 through May 2026, this report captured 199,565 emergency department visits involving CHS. The rate held relatively flat — around 3.35 per 10,000 ED visits — through September 2025. When a dedicated ICD-10-CM diagnosis code took effect on October 1, 2025, the monthly rate jumped immediately to 11.26 per 10,000 visits, a single-month tripling. Over the following eight months (October 2025–May 2026), average monthly CHS-involved ED visits ran 3.7 times the pre-code baseline. Younger adults aged 15–24 and females showed disproportionately high proportions, with some demographic subgroups exhibiting even sharper post-implementation increases.
This surveillance finding is methodologically important but requires careful interpretation. The near-instantaneous rate spike is almost certainly a coding artifact — clinicians who had long struggled to document CHS now had a precise code available — rather than a sudden epidemic surge. However, the magnitude of the change strongly implies that pre-2025 CHS prevalence was systematically undercounted, possibly by a factor of three or more. From a broader clinical landscape perspective, CHS has been documented since 2004 but remained poorly integrated into emergency medicine workflows; its hallmark relief from hot bathing is still frequently missed in busy EDs. The demographic skew toward younger adults is consistent with earlier cohort studies linking high-frequency cannabis use patterns to syndrome onset. A critical limitation is that syndromic surveillance captures ED encounters, not incidence in the community — the population suffering CHS without seeking emergency care remains entirely invisible to this dataset. Nonetheless, the creation of this code represents an incremental but meaningful infrastructure advance that should improve future comparative epidemiology and potentially accelerate recognition at the point of care.