Cannabis in 84% of teens' substance-related ER visits, WashU study finds

Cannabis was involved in most substance-related emergency visits and hospital stays among American teenagers and young adults, while alcohol dominated among older adults, according to a study by researchers at Washington University School of Medicine in St. Louis (WashU Medicine) published on Wednesday, 4 November 2026 in The American Journal of Psychiatry. The team looked at United States acute care records from 2016 to 2023. Among people aged 16 to 18 who needed substance-related acute care, 84% had an encounter that involved cannabis.

The study gives a picture of which substances send people of different ages to hospital, rather than which substances they say they use in surveys. For young people the answer is now mostly cannabis; for older adults it is still mostly alcohol. The two substances cause different kinds of acute problems, so the split matters for how hospitals prepare.

Two of the problems the team flagged are worth explaining. Psychosis is a state in which a person loses touch with reality, for example hearing voices or holding false beliefs. Cannabinoid hyperemesis syndrome is a condition tied to cannabis use in which a person has repeated bouts of severe vomiting. Both can bring a young person to an emergency department. In WashU Medicine's account of the work, Xu pointed to the high strength of many cannabis products sold today as a particular concern for brains that are still developing.

The study has clear limits, and the authors set them out. An encounter was counted as cannabis-involved if cannabis appeared anywhere in the list of diagnoses, so the visit may have been mainly about something else. Nearly half of the cannabis-involved encounters also involved another substance. The records come only from the United States, so the findings describe that country and cannot be read across directly to others, including India.

For students and first-jobbers, the useful point is narrower than the headline: the age group that showed the steepest rise, 19 to 24, is the college and early-career group. The study measures hospital visits, not everyday use, so it says nothing about how common cannabis use is in any campus or city.

Peepals calculation: if the cannabis share among 19 to 24 year olds grew by 1.81 percentage points every year across the seven yearly steps from 2016 to 2023, the total rise is about 12.7 points (1.81 × 7 ≈ 12.7), against about 5.8 points for 16 to 18 year olds (0.83 × 7 ≈ 5.8), so the young-adult rise was roughly 2.2 times as steep (1.81 ÷ 0.83 ≈ 2.2). Among 16 to 18 year olds, cannabis appeared in about 2.5 times as many substance-related encounters as alcohol (84 ÷ 33 ≈ 2.5). Our calculation from the reported figures.

Short-term: Emergency teams in the United States may see the findings as support for asking young patients about cannabis as routinely as they ask about alcohol, since the two substances present in different ways.

Long-term: Prevention work aimed at young people may need to give cannabis more attention, while programmes for older adults stay focused on alcohol. The authors' data on psychosis and vomiting admissions adds to wider research interest in the effects of high-strength products.

Who is affected: Teenagers and young adults, their families, college health services, emergency doctors and public health planners, mainly in the United States.

Questions and Answers