Archive restoration — 26 September 2026: This article has been restored from our original source files. Its publication date and reporting context remain unchanged; it is not a new update on current policy, availability or clinical guidance.
Cannabis can reduce nausea in some clinical settings. In a smaller group of people who use it frequently, it can produce the opposite effect: repeated episodes of severe vomiting, abdominal pain and dehydration.
That contradiction is one reason cannabinoid hyperemesis syndrome, or CHS, is so often misunderstood. A person may have used cannabis for years without difficulty. They may feel that it briefly settles their nausea. They may also have received it on prescription. None of those facts automatically rules CHS out.
New surveillance from the US Centers for Disease Control and Prevention gives the clearest recent picture of how often the syndrome is appearing in emergency-department records. Between January 2023 and May 2026, researchers identified 199,565 emergency visits involving CHS across the consistently reporting facilities in their dataset.
The number is important. It is also easy to misuse. The report does not show that CHS suddenly became almost four times more common in late 2025, even though the recorded rate appeared to rise by that amount. Much of the jump followed the introduction of a diagnosis code that finally allowed clinicians to record the syndrome by name.
The useful story is therefore not a panic about a new epidemic. It is that a serious, preventable cannabis-related condition has probably been hidden inside broader vomiting diagnoses for years—and clinicians are getting better at recognising it.
What the CDC report found
The CDC analysed near-real-time records from its National Syndromic Surveillance Program, which receives data from emergency departments across the United States. For its trend analysis, the team included 3,636 facilities that reported consistently between January 2023 and May 2026.
Before October 2025, there was no dedicated US diagnosis code for CHS. Researchers had to identify likely cases by combining codes for cyclical or non-specific vomiting with a separate cannabis-related code.
Using that earlier definition, the monthly rate was relatively stable. It measured 3.19 CHS-involved visits per 10,000 emergency visits in January 2023 and 3.35 per 10,000 in September 2025.
On 1 October 2025, a specific code—R11.16—came into use. The recorded rate rose immediately to 11.26 per 10,000 visits, then remained around that higher level. Across the following eight months, the monthly average was 11.97 per 10,000: 3.7 times the average recorded under the earlier system.
Young people had the highest recorded proportions. From October 2025 to May 2026, CHS was identified in an average of 38.70 per 10,000 emergency visits among people aged 15 to 24 and 28.28 per 10,000 among those aged 25 to 34. The rate was also slightly higher among females than males.
These figures describe visits, not individual patients. Someone returning to hospital during multiple episodes can appear more than once. The data also do not establish how many cannabis users develop CHS because the CDC did not have a denominator showing the number, frequency or pattern of people using cannabis.
Why the apparent rise needs careful language
An abrupt increase on the exact date a new diagnosis code appears is not evidence that the underlying illness abruptly increased on that date.
The CDC says the change probably reflects improved recognition and coding, at least in part. Before the dedicated code, a clinician could recognise recurrent vomiting but fail to add a cannabis-related diagnosis. Another might record cyclical vomiting syndrome instead. Both situations would leave a genuine CHS presentation outside the earlier case definition.
The newer figures may therefore be closer to the true burden in emergency departments. They cannot be compared directly with the older figures as though the surveillance method remained unchanged.
This distinction matters because “CHS visits rise 270%” would be a dramatic but unreliable headline. The defensible conclusion is narrower: once hospitals had a specific way to name CHS, they recorded substantially more of it than the previous proxy method captured.
That still has public-health significance. Better coding makes the condition more visible, allows patterns to be monitored and may shorten the cycle of repeated hospital visits before a patient receives a plausible explanation.
What CHS looks like
The Royal College of Emergency Medicine describes CHS as episodic, cyclical vomiting associated with prolonged cannabinoid use. A typical pattern can include:
- recurrent episodes of severe nausea and vomiting, separated by periods of feeling relatively well;
- abdominal pain;
- regular cannabis use, often weekly or more frequently and sometimes extending over years;
- temporary relief from hot showers or baths; and
- improvement after sustained cannabis cessation, with symptoms returning if cannabis is resumed.
Some people experience a prodromal phase before the severe vomiting begins. Early-morning nausea, abdominal discomfort and fear of vomiting can continue for weeks or months. Because cannabis may seem to relieve nausea in the short term, a person may respond by using more of it, unintentionally reinforcing the exposure associated with the syndrome.
Hot bathing is a distinctive clue, but it is not proof. Not everyone with CHS reports it, and other conditions can produce recurrent vomiting. There is no blood test or scan that confirms CHS. Clinicians still need to consider infection, pregnancy, bowel or abdominal disease, diabetic gastroparesis, neurological causes and cyclical vomiting syndrome, among other possibilities.
The diagnosis is often only confirmed retrospectively when episodes resolve after sustained cessation. That is why the Royal College advises emergency clinicians to think in terms of suspected CHS while investigating dangerous alternatives.
What the report cannot tell us about risk
The CDC records did not include reliable information about product type, dose, THC concentration, route of administration or whether the cannabis was used medically or recreationally.
They therefore cannot answer whether flower, vapes, concentrates or oral products carry different levels of risk. Nor can they establish a safe threshold below which CHS will not occur.
Frequent use is the clearest recurring feature, but even that does not explain why only some regular users develop the syndrome. Genetics, cannabinoid exposure, product potency, metabolism and other biological or behavioural factors remain under investigation.
The age pattern also needs context. A higher proportion of emergency visits among younger people could reflect more frequent use, higher-potency products, earlier initiation, different routes of administration or differences in clinical recognition. The surveillance study cannot separate those explanations.
Most importantly, this was US emergency-department surveillance. It does not estimate UK prevalence, and differences in products, healthcare access, coding and prescribing mean the figures cannot simply be transferred to Britain.
What it means for prescribed medical-cannabis patients
A prescription does not make recurrent vomiting unimportant, but neither should a patient abruptly alter treatment because they have read about CHS.
The new report did not distinguish prescribed use from non-medical use, so it cannot quantify the risk for UK medical-cannabis patients. A clinician assessing possible CHS still needs the full exposure history: frequency, duration, formulation, dose, route and any recent changes.
Patients may be particularly reluctant to consider cannabis as a cause when it is controlling pain, spasticity, nausea or another difficult symptom. That reluctance is understandable. Stopping can mean the return of the condition being treated, withdrawal symptoms or both.
The appropriate response is a non-judgemental review with the prescribing clinic or medical team. Recurrent vomiting should not be dismissed as an expected side effect, and the possibility of CHS should not be used as a shortcut that prevents clinicians investigating other causes.
If CHS is suspected, any change to a prescribed treatment should be planned with the prescriber whenever the situation is not an emergency. During severe vomiting, urgent assessment takes priority.
Our analysis of medical cannabis in NHS hospitals explains why accurate medication records and early contact with the prescribing clinician matter during an admission.
Why treatment can be difficult
CHS is known for responding poorly to some standard anti-sickness medicines. In hospital, treatment may include intravenous fluids, correction of electrolyte abnormalities and assessment for kidney injury or another cause of the symptoms.
The Royal College of Emergency Medicine says clinicians can consider haloperidol or topical capsaicin when routine treatment has not controlled the symptoms. The supporting trials are small, and both interventions require appropriate clinical checks. They are not do-it-yourself treatments.
Hot showers or baths can offer temporary relief, but they do not treat the cause and can add to dehydration when used repeatedly during an episode.
Current guidance is much firmer about prevention than acute symptom control: sustained abstinence from cannabis is the only intervention identified as preventing further CHS episodes. Cutting down may reduce exposure, but UK patient guidance does not regard it as a reliable way to stop recurrence.
That advice can be clinically complicated for someone who is dependent on cannabis or using a prescribed product for severe symptoms. A credible care plan needs to address both problems—the vomiting and what happens when cannabis is withdrawn—rather than presenting cessation as a single effortless decision.
When to seek help
Repeated vomiting can cause dehydration, electrolyte disturbance and acute kidney injury. Rare complications can include heart-rhythm problems, seizures and shock.
University Hospital Southampton advises contacting a healthcare provider after severe vomiting lasting a day or more. In the UK, NHS 111 can advise where to seek care. Someone who cannot keep fluids down, is becoming faint or confused, has very little urine, severe or worsening abdominal pain, blood in vomit, or another alarming symptom should seek urgent medical assessment.
When speaking to a clinician, disclose cannabis and cannabinoid use accurately—including prescribed products. Route, frequency, approximate dose, duration and the timing of the most recent use can all help. The Royal College explicitly advises clinicians to handle that disclosure confidentially and without stigma.
What better recognition should look like
Recognition should not mean that every person who uses cannabis and vomits is labelled with CHS. It should mean that clinicians ask the question early, investigate other serious causes and recognise a recurring pattern when it is present.
It should also improve the conversation patients receive. Being told “cannabis is doing this” may sound implausible when the same substance sometimes relieves nausea. Explaining the paradox, the episodic course and the importance of cessation is more useful than blame.
For prescribed patients, clinics should make CHS part of routine safety information without implying that it is inevitable. Follow-up should ask about morning nausea, abdominal pain, recurrent vomiting and hot bathing, particularly when use is frequent or doses have increased.
The UK also needs better data. Emergency departments could audit suspected cases, repeat attendance, product type and prescribed status. Without that information, discussion will continue to rely heavily on North American surveillance and small clinical series.
The editorial view
The new CDC report makes CHS harder to treat as an obscure curiosity. Almost 200,000 recorded emergency visits over three years demand attention.
But the coding change is the centre of the story, not a statistical inconvenience. It means the report cannot prove a sudden surge in illness. Its strongest finding is that the older system appears to have missed a substantial amount of recognised or suspected CHS.
Responsible cannabis coverage has to make room for that finding. Medical use and harm are not mutually exclusive. A substance can help one symptom, cause another and require different decisions for different people.
Patients do not benefit when CHS is minimised to protect the reputation of cannabis. They also do not benefit when surveillance data are inflated into a general claim that cannabis is sending users to hospital in rapidly multiplying numbers.
The useful middle ground is practical: recognise the pattern, investigate properly, communicate without stigma and treat recurrent vomiting as a medical problem rather than a moral judgement.
Key takeaways
- CDC surveillance identified 199,565 US emergency-department visits involving cannabinoid hyperemesis syndrome between January 2023 and May 2026.
- The recorded monthly rate became 3.7 times higher after a dedicated CHS diagnosis code was introduced in October 2025.
- That abrupt increase probably reflects better recognition and coding; it does not prove that the true incidence suddenly tripled.
- CHS involves recurrent severe nausea, vomiting and often abdominal pain in the context of prolonged, frequent cannabinoid use.
- Hot showers may temporarily relieve symptoms but do not treat the cause and can worsen dehydration.
- The CDC data do not identify product type, dose, potency, route or prescribed status, so they cannot quantify risk for UK medical-cannabis patients.
- Severe or persistent vomiting needs medical assessment. Sustained cannabis cessation is currently the only established way to prevent CHS recurrence.
Sources
- Trends in emergency-department visits involving cannabinoid hyperemesis syndrome, January 2023–May 2026 — CDC Morbidity and Mortality Weekly Report
- Suspected cannabinoid hyperemesis syndrome in emergency departments — Royal College of Emergency Medicine
- Cannabinoid hyperemesis syndrome: patient information — University Hospital Southampton NHS Foundation Trust
- Cannabinoid hyperemesis syndrome: patient information — East Kent Hospitals University NHS Foundation Trust
- Emergency-department visits with cannabis-related diagnoses, cyclical vomiting syndrome and cannabinoid hyperemesis syndrome, 2016–2022 — JAMA Network Open
- Cyclical vomiting syndrome — NHS
