It’s a gamble for your health.

A popular online pastime is proving to be a bad bet for some players, with new research linking its rise to a spike in emergency-room visits — and one demographic getting hit particularly hard.

The findings, from Canada, could be a warning sign for the US, where the activity has taken off in recent years.

In the study, researchers from the University of Toronto and other institutions zeroed in on single-event online sports betting.

Canada legalized it in August 2021, and Ontario opened the door to private operators the following April, becoming the first province to allow them to compete alongside the government-run platform.

The move has proved to be a cash cow. In 2024 alone, Ontarians wagered $82.7 billion through 2.6 million player accounts.

To gauge the fallout, researchers analyzed emergency department visits for gambling disorders among Ontarians ages 10 to 105 over 14 years, before and after the rule changes.

In all, 757 people made 952 ER visits during that time in which a gambling disorder was listed as either the main or a contributing reason for the trip.

After Canada legalized single-event sports betting and Ontario expanded its gambling market, gambling-related ER visits doubled.

But the impact wasn’t evenly spread. Visits were 154% higher than expected among males ages 10 to 29 and 116% higher among males ages 30 to 44.

Notably, there were no changes among females.

Many of the patients arrived at the ER with major depression or suicidal thoughts, while others had mental-health or substance-abuse diagnoses.

Nearly one-third of the emergency department visits resulted in a hospital admission.

“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,” Daniel Myran, senior author of the study and an associate professor of family and community medicine, said in a news release.

The findings come as online sports betting has become increasingly woven into American life since the US Supreme Court struck down a federal law barring most state-authorized sports gambling.

Today, 27% of US adults — including half of men ages 18 to 49 — say they have an active account with an online sportsbook such as DraftKings, Caesars, FanDuel or BetMGM, according to an April 2026 study.

That’s up from 22% of Americans in 2025 and 19% in 2024.

Most bettors still say they do it because it’s fun and exciting, makes them more interested in watching games live or because they think they can make money placing bets.

But the same survey points to some troubling trends.

Negative gambling outcomes have ticked up in several areas, per the Siena Research Institute and St. Bonaventure University’s Jandoli School of Communication.

This year, 42% of sports bettors said they felt they wagered more than they should, up from 37% last year. And 43% said they felt bad or ashamed after losing a bet, up from 37% in 2025.

Fifteen percent of bettors said they had called a problem gambling helpline or sought other help, up from 9% in both 2025 and 2024.

Meanwhile, 22% of respondents said they know someone who has or has had a problem with online sports betting — up from 16% in 2025 and 15% in 2024.

Since the Supreme Court decision, states have been left to make their own rules for online sports betting.

Currently, 32 states and Washington, DC, have legal sports betting programs through smartphone apps or websites, according to CBS Sports. New York is among them — and it’s a particularly big player.

In September, a report found that sports wagering had become the Empire State’s second-biggest revenue generator from the gaming industry, bringing in more than $1 billion a year in taxes and trailing only the lottery.

The surge in gaming revenue in recent years is largely attributable to the rise of mobile sports betting, while other forms of gambling have declined or remained flat, according to an analysis from state Comptroller Tom DiNapoli’s office.

And as concerns about gambling addiction have spread nationwide — particularly among young men — New York hasn’t been an exception.

As online wagering has increased, calls to the state’s problem gambling support hotline jumped 8.5% between 2020 and 2025, reaching 2,545 last year.

In neighboring New Jersey, where online sports betting is also legal, nearly one in five adults ages 18 to 24 is at high risk for problem gambling — and a third of that group gambles exclusively online, Rutgers University researchers found.

That rate is five times higher than in a 2017 report from the school and higher than that of any other age group.

Younger men ages 18 to 44 were also “most likely to be high-risk problem gamblers,” according to the report, which found that 19% of those ages 18 to 24 were at high risk.

The latest research points to a similar fallout in Canada in the five years since single-event sports betting became legal.

“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,” said Ryan Forrest, first author of the study and a doctoral student at the Dalla Lana School of Public Health.

“The consequences of rising gambling involve not just harm to people who are gambling but wider effects on families and communities.”