Canada legalized single-event sports betting in August 2021, and in April 2022 Ontario became the first province to let private companies run online gambling alongside the government platform. A study in the September issue of The American Journal of Preventive Medicine measures what happened next at the most severe end of the harm curve: people arriving in hospital emergency departments with a gambling disorder.

The design is about as complete as a natural experiment gets here — the whole population, not a sample:

  • Population-based interrupted time series covering everyone in Ontario aged 10 and older eligible for universal health coverage: 17,353,640 people, from January 2012 to June 2025.
  • Across 14 years there were 952 emergency department visits for gambling disorders, from 757 individuals. Mean age 41.8 years; 72% male.
  • Visits were stable before liberalization, and did not jump when the market opened. They began climbing afterwards, at roughly 7% per quarter (incidence rate ratio 1.07, 95% CI 1.04–1.10).
  • By April–June 2025 the rate was 99% higher than the same period would have been without liberalization (IRR 1.99, 95% CI 1.48–2.67).
  • The increase is entirely male. Men went from 1.81 to 2.63 visits per million (average quarterly rates 31.3% higher in the post-liberalization period); the female rate did not move (0.77 to 0.74 per million).
  • By age at the end of the study period: 154% higher than expected among men aged 10–29 (IRR 2.54, 95% CI 1.15–5.63) and 116% higher among men 30–44 (IRR 2.16, 95% CI 1.18–3.95).

These were not mild presentations. More than 70% of the emergency visits involved another mental health condition or heavy substance use, and almost a third led to hospital admission.

Why the emergency data carries weight

The same research team previously reported a large increase in gambling-related contacts to ConnexOntario, the province’s mental health and addiction helpline, after the market expanded. That finding had an obvious innocent explanation: Ontario requires gambling advertisements and betting sites to display helpline contact information, so rising awareness could account for rising calls.

Emergency departments are not advertised as a source of gambling support. The authors treat the ED trend as the more robust signal for exactly that reason — and the two datasets now point the same way.

The market this happened in

  • Ontario’s regulated online market has 83 gaming and betting sites run by 43 private companies, including some of the largest multinational gambling corporations.
  • In 2024, Ontarians wagered $82.7 billion CAD across 2.6 million player accounts.
  • Alberta allowed private online operators in July 2026 — the second province to do so — and the authors say other regions are under pressure to follow.

What the study does and does not show

The authors state the limit themselves: these visits are rare. Before expansion the rate was roughly 1.3 per million per year, so a doubling is a doubling of a small base — a few hundred visits across a population of 17 million — and the “expected” comparison is modelled from pre-liberalization trends rather than observed. This is one province, an observational design, and a clinical endpoint that only catches the people who reach an emergency department.

That last point cuts the other way, and the authors say so. First author Ryan Forrest: “The concentration of the increase among younger males is particularly concerning given the rapid growth and promotion of online sports betting, which target this demographic.” Senior author Daniel Myran is blunter about the denominator: “Most people experiencing gambling problems will never seek care, so the concern is that the increases in emergency department visits for gambling disorders we observed may be revealing much larger increases in gambling-related harm.”

Myran’s recommendation for jurisdictions considering the same expansion is not prohibition but safeguards: restrictions on marketing and on the higher-risk forms of gambling, alongside better recognition and treatment of gambling-related harms.