HMN 2025: How Chronic cannabis use, vomiting and compulsive bathing are symptoms of a hidden syndrome

Researchers at the Jane Addams College of Social Work at the University of Illinois Chicago have found that cannabinoid hyperemesis syndrome, a vomiting condition tied to chronic cannabis use, rose sharply in US emergency departments between 2016 and 2022 and has stayed elevated.

Once a mystery illness

As of June 2025, nearly half of US residents live in states with legalized recreational cannabis, and policy shifts have expanded adult-use access through legalization, medical programs, and decriminalization. Among cannabis-related harms, cannabinoid hyperemesis syndrome (CHS) has been described as a growing concern in clinical and public health settings.

CHS was first identified in 2004 in Australia and remains a syndrome with uncertain etiology. Proposed neurophysiological mechanisms include downregulation of cannabinoid 1 receptors, altered transient receptor potential vanilloid 1 signaling, and disrupted hypothalamic thermoregulation.

CHS has three defined phases. The first two include a prodromal phase of abdominal pain or morning nausea which can last for months or years at a time, and a hyperemetic phase, lasting a few days with recurrent vomiting and potential escalation to “scromiting” where screaming in pain while vomiting can occur.

Within these phases, people with CHS tend to bathe compulsively in hot water, often for hours at a time, as it can relieve symptoms.

In a third, recovery phase, abstinence from cannabis reduces symptoms within a few days or months. Eventually, they will completely disappear.

The existence of CHS was a mystery to clinicians until very recently. Patients with CHS frequently appear in emergency departments and are often tested unnecessarily for a wide variety of conditions, misdiagnosed with cyclic vomiting syndrome or assigned nonspecific gastrointestinal conditions.

Before a specific diagnostic label existed, CHS could be inferred from combinations of vomiting-related codes and cannabis-related codes. A dedicated International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) code for CHS, F12.188, became available only with the 2025 update.

In the study, “Cannabinoid Hyperemesis Syndrome, 2016 to 2022,” published in JAMA Network Open, researchers conducted a cross-sectional analysis to estimate CHS prevalence in US emergency departments, assess temporal trends from 2016 to 2022, and examine sociodemographic associations.

Analyses used the Nationwide Emergency Department Sample (NEDS), part of the Healthcare Cost and Utilization Project sponsored by the Agency for Healthcare Research and Quality. NEDS provides a stratified 20% sample of all visits to hospital-owned emergency departments in participating US hospitals, along with survey weights designed to yield nationally representative estimates.

Annual emergency department visit counts in NEDS ranged from 28.3 million visits in 2020 to 35.8 million visits in 2018, with weighted national estimates between 123.3 million in 2020 and 144.8 million in 2016 and 2017. In 2022, 993 hospitals across 41 states and the District of Columbia contributed, representing approximately 84.7% of the US population and 83.9% of all emergency department visits.

CHS in emergency care

Survey-weighted descriptive analyses showed that CHS patients were substantially younger than patients in comparison groups. CHS visits had a mean age of 30.6 years, compared with 36.7 years for cannabis use disorder only, 37.6 years for cyclic vomiting syndrome, and 48.1 years for visits without either diagnosis.

Age groupings showed CHS clustering in younger adults. Among CHS patients, 35.7% were aged 18 to 25 years and 31.5% were aged 26 to 35 years.

Overall, visits and cyclic vomiting syndrome visits showed female predominance, while cannabis use disorder visits showed clear male predominance. CHS visits had a nearly even sex distribution, with 50.8% female and 49.2% male.

Regionally, CHS visits were more prominent in the West and Northeast compared with the South, which held the largest overall share of emergency department visits at 39.9% but a smaller share of CHS visits. Black patients accounted for 24.7% of CHS visits.

Co-occurring noncannabis substance codes were uncommon in CHS visits. Alcohol codes appeared in 3.57%, opioids in 1.58%, cocaine in 1.77%, and stimulants in 1.10%. Any of these noncannabis substances appeared in 7.21% of CHS visits.

Changes over time

Patterns revealed distinct trends for cannabis-related diagnoses, cyclic vomiting syndrome, and CHS. Between 2016 and 2022, use disorder visits increased from 1,008 to 1,465 per 100,000 emergency department visits. CHS visits rose from 4.36 to 22.33 per 100,000 visits during that period, peaking at 33.06 per 100,000 in quarter 2 of 2020. Cyclic vomiting syndrome visits declined from 300 to 186 per 100,000 visits, perhaps suggesting a growing clinical awareness of CHS.

Models restricted to visits with primary cyclic vomiting syndrome diagnoses examined the conditional probability of CHS among those cyclic vomiting syndrome visits. Across demographic groups, the probability of CHS among cyclic vomiting syndrome-coded visits increased over time, with especially sharp increases among patients aged 18 to 25 years and 26 to 35 years.

Smoothed quarterly estimates using restricted cubic splines showed the conditional CHS probability among cyclic vomiting syndrome visits rising after quarter 2 of 2020, peaking in 2021, and then tapering through 2023 while remaining above 2019 levels. Survey-weighted probabilities rose from 3.3% in 2019 to 6.9% in 2020 and reached 13.2% in 2021, before decreasing to 9.7% in 2023.

Factors linked with higher CHS risk

Female sex was associated with a slightly lower CHS risk relative to male sex, with a relative risk ratio of 0.92, while being associated with a higher risk of cyclic vomiting syndrome and lower risk of use disorder. Age showed strong associations, with patients aged 18 to 25 years described as more than three times more likely to receive a CHS diagnosis compared with those aged 36 to 50 years.

Awareness and care

Investigators noted a paradox in the absence of a pronounced CHS increase before 2020 despite expanding legalization and rising availability of high-potency products. Underdiagnosis or misclassification before broader clinical recognition of CHS was proposed as one possible explanation, alongside increased exposure and heightened diagnostic vigilance during and after the pandemic.

Study authors argue that emergency clinicians and public health systems need preparation for the consequences of increased cannabis use, particularly in regions where legalization is recent and exposure to high-potency cannabis products is expanding. CHS may be underrecognized in those settings, with failure to identify the syndrome contributing to unnecessary diagnostic testing and ineffective treatment courses.

Clinical guidelines to increase awareness and decision-support tools are possible strategies to help clinicians distinguish CHS from other gastrointestinal conditions, especially among younger adults with chronic cannabis exposure. Targeted screening for cannabis use and careful attention to symptom patterns, including recurrent severe nausea, vomiting, abdominal pain, and compulsive hot bathing, are suggested as ways to improve diagnostic accuracy.

A new ICD-10 code for CHS, F12.188, may facilitate surveillance and tracking, yet it depends on clinician recognition and consistent application. Investigators called for validation studies to help separate true changes in incidence from coding shifts and misdiagnosis.

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