Cannabis Today: Hyperemesis, Psychosis Risk and Quadrupled Potency

Average THC content in seized cannabis rose from 3.96 percent in 1995 to 16.14 percent in 2022, and dispensary concentrates can exceed 40 percent. Two consequences of that shift now show up in emergency departments: a vomiting syndrome that did not have its own diagnostic code until October 2025, and a documented association with psychosis that scales with potency.

Cannabis hyperemesis syndrome

CDC describes it as sudden episodes of severe nausea, vomiting and abdominal pain, cyclical in nature, associated with prolonged frequent cannabis use. Outcomes range from resolution after stopping cannabis to, rarely, death. The classic clinical feature, widely reported, is that symptoms are relieved by hot showers.

Two findings from CDC surveillance are worth knowing. Symptom onset can occur within the first year of use, earlier than previously believed. And the syndrome is frequently misdiagnosed as cyclical vomiting syndrome, which means people can spend a long time being investigated for something else.

A dedicated diagnostic code took effect on October 1, 2025, and the data since then is instructive. Between January 2023 and May 2026, CDC counted 199,565 emergency department visits involving the syndrome out of more than 407 million all-cause visits. The measured proportion jumped from 3.35 per 10,000 visits in September 2025 to 11.26 per 10,000 in October 2025, and averaged 11.97 per 10,000 from October 2025 to May 2026, about 3.7 times the earlier average of 3.19.

That jump needs the caveat CDC itself attached: it likely reflects, at least in part, improved clinical recognition and coding rather than a true and immediate rise in incidence. A new code makes a condition visible; it does not create cases. Anyone reporting a 3.7 fold increase in the condition itself is misreading the data.

Highest proportions were among people aged 15 to 24, at 38.70 per 10,000 visits, among Black patients at 17.60, and among females at 12.65.

Potency, and why it changes the risk calculation

The potency trend comes from NIDA’s monitoring program analyzing law enforcement seizures: delta-9 THC rose from 3.96 percent in 1995 to 16.14 percent in 2022, roughly a quadrupling. Concentrates sold in dispensaries can exceed 40 percent.

CDC notes that higher THC concentration, above 10 percent, is associated with continued and more frequent cannabis use among adolescents and young adults. This is the reason comparisons to what cannabis was like decades ago are not useful as a guide to current risk. The product changed.

The psychosis association

The strongest evidence comes from a study of 901 first episode psychosis patients across 11 sites in Europe and Brazil, published in Lancet Psychiatry in 2019. Compared with people who had never used cannabis, daily cannabis use carried an adjusted odds ratio of 3.2, with a 95 percent confidence interval of 2.2 to 4.1. Daily use of high potency cannabis carried an adjusted odds ratio of 4.8, confidence interval 2.5 to 6.3.

The dose response pattern is the part that matters. Risk was higher for daily use than occasional use, and higher again for daily high potency use. That gradient is what makes the association harder to dismiss as confounding alone.

Some care is warranted in how this is stated. These are case control findings showing association. They do not establish that cannabis causes psychosis in any individual, and the direction of effect in people already predisposed remains debated. What they do establish is that daily high potency use sits in a substantially higher risk group.

Youth and young adult use

Two different age groups are moving in different directions, and conflating them produces bad reporting.

Among adolescents, use has been broadly stable. The 2025 Monitoring the Future survey reported that adolescent use of most substances stayed near the historic low reached in 2021 for the fifth consecutive year, with cannabis use remaining stable across grades. We flag that the specific twelfth grade figure we saw, 26 percent past year use, came from secondary reporting rather than the survey volume itself.

Among young adults, the direction differs. CDC notes that past month and daily or near daily cannabis use has been increasing, particularly among young adults and females. Teens stable, young adults rising: those are two separate findings about two separate populations.

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Takeaways

• THC in seized cannabis rose from 3.96 percent in 1995 to 16.14 percent in 2022; concentrates can exceed 40 percent.
• Cannabis hyperemesis syndrome causes cyclical severe vomiting, is relieved by hot showers, and is often misdiagnosed.
• A dedicated diagnostic code began October 2025. The apparent jump in cases largely reflects better coding, as CDC states.
• Onset can occur within the first year of use, earlier than previously believed.
• Daily cannabis use carried an adjusted odds ratio of 3.2 for first episode psychosis; daily high potency use 4.8.
• Adolescent use is broadly stable while young adult use is rising. These are different findings and should not be merged.

Sources

Vivolo-Kantor AM and colleagues, Trends in Emergency Department Visits Involving Cannabis Hyperemesis Syndrome Identified Using a New Diagnosis Code, Morbidity and Mortality Weekly Report, 2026, using the National Syndromic Surveillance Program. National Institute on Drug Abuse, Cannabis research topic page, and the Potency Monitoring Program. ElSohly MA, Majumdar CG, Chandra S, Radwan MM, Frontiers in Public Health, 2024. Di Forti M and colleagues, Lancet Psychiatry, 2019. Hines LA and colleagues, JAMA Psychiatry, 2020. Monitoring the Future national survey results, 2025.