Cannabis Hyperemesis Syndrome in the ER: A New Diagnosis Code Reveals a Bigger Toll

Cannabis hyperemesis syndrome (CHS) brings sudden bouts of severe nausea, vomiting and abdominal pain in people with prolonged, frequent cannabis use. Symptoms can be debilitating: many people end up seeking care, and outcomes range from recovery after stopping cannabis to, rarely, death. Suspected cases rose sharply from 2016 to 2022, especially during the COVID-19 pandemic, as many states legalized cannabis — though it remains illegal under federal law.

CHS has likely been under-recognized: clinicians may not ask about or record cannabis use, and CHS can be mistaken for other conditions such as cyclical vomiting syndrome. On October 1, 2025, it got its own diagnosis code, ICD-10-CM R11.16. CDC compared emergency department (ED) visits before and after.

The jump

CHS-involved ED visits per 10,000 visits, January 2023–May 2026. Image from CDC's report

From January 2023 to May 2026, 199,565 ED visits involved CHS.

Such an abrupt, lasting jump — after years of stable numbers in every group — most likely reflects better recognition and coding, not a sudden surge in cases. But the higher figures may also be the more accurate picture of CHS's toll.

Who is affected

CHS-involved ED visits by age, sex, and race and ethnicity. Image from CDC's report

Average monthly CHS-involved visits per 10,000 ED visits, October 2025 – May 2026:

Before the code, the highest rates were also among people 15–24 (9.99), females (3.28) and American Indian or Alaska Native people (4.33).

Why young people?

CHS has been seen as a condition of heavy use over many years, but newer evidence shows symptoms can begin within the first year of use — and diagnosis can lag symptoms by years. High rates among the young may reflect:

• starting earlier
• more high-potency THC products — THC levels in cannabis have risen over time, and potency above 10% is linked to more frequent use by teens and young adults, the main risk factor for CHS
• new ways of using, such as vaping or dabbing
• changing perceptions of risk, and more frequent use

Past-month and daily or near-daily cannabis use has been rising, particularly among young adults and females.

What to do

• Clinicians can consider CHS in patients with nausea, vomiting and abdominal pain, and ask routinely about cannabis use — how often, for how long, which products and how they're used. Screening for substance use disorders and psychiatric conditions may also be warranted.
• Education should reach younger people in particular: CHS can follow shorter use than once thought. CDC's ENGAGE resource lists evidence-based ways to prevent youth substance use, and CDC explains the health effects of cannabis.
• Surveillance should continue, including the role of high-potency THC and hemp-derived products.

How the data were gathered

CDC's National Syndromic Surveillance Program draws near real-time health record data from about 7,500 facilities in all 50 states, D.C. and Guam — 83% of U.S. EDs. The analysis used the 3,636 EDs that reported consistently. Before October 2025, CHS was flagged by pairing a vomiting code with a cannabis-related code; afterward, by the new code or the old pairing.

Limits: the old codes were imprecise; even the new one depends on clinicians recognizing and recording CHS; only people sick enough for the ER are counted; cannabis use is often self-reported; and the consistently reporting EDs may not represent all.

Sources

Based on Alana M. Vivolo-Kantor, Stephen Liu, Lauren J. Tanz, Christine L. Mattson and Josh Schier, "Trends in Emergency Department Visits Involving Cannabis Hyperemesis Syndrome Identified Using a New Diagnosis Code — United States, January 2023–May 2026," MMWR, volume 75, Centers for Disease Control and Prevention; a work of the United States government in the public domain.