More than 40% of American teens ages 13 to 17 say they’ve gambled in the past year, according to a survey published Wednesday, raising red flags about the popularity of betting among minors.

Researchers from Rutgers University’s Center for Gambling Studies surveyed nearly 1,700 Americans between 13 and 27, and found that 52.5% of the respondents said they had gambled. Among those 17 and under — for whom gambling is illegal — the share was nearly 43%.

“We are living in a time where anyone can have a casino or sports book in their pocket,” said Lia Nower, the director of the Rutgers center and lead author of the new report. “Now teens who should be playing sports are betting on them, often with family members.”

Nower and her colleagues conducted the survey over the spring and early summer, describing the effort as the first national gambling prevalence study of U.S. adolescents and young adults in nearly 20 years.

The report does not offer a comparison to past gambling trends, so it is difficult to assess whether the results represent an increase.

In an interview, Nower referenced a 2007 study in the Journal of Gambling Studies, which found that 68% of respondents between 14 and 21 had gambled in the past year. The numbers can’t be compared apples to apples, however, as the methodologies and age ranges differed.

Still, the prevalence of problem gambling in the new report appears to be higher than in the 2007 study.

Of the respondents who reported gambling activity, nearly 40% “showed symptoms of problem gambling,” the report says, and 10% could be considered “high-risk problem gamblers.”

Among teens 17 and under who said they gambled, about 11% were classified as “high risk for problems,” according to the report.

“Gambling is no longer confined to casinos and lottery tickets. It is increasingly embedded in video games, sports broadcasts and other products young people can access,” Nower said. “We have worried this would increase rates of problem gambling among youth. Now we know. It does.”

She described the findings as cause for alarm.

“Gambling has an operant conditioning component that results in some people getting addicted over time,” Nower said. “Most people who start young bet small amounts with friends or family and then increase the number of activities, frequency and amounts wagered over time.”

The Rutgers researchers classified gambling fairly broadly to include 21 activities, such as street games, lottery tickets, games of skill, cryptocurrency trading and prediction markets — “anything where money is wagered,” Nower said.

That definition was based on a similar one in a 2017 study, she added: “Staking money or something of material value on an event having an uncertain outcome in the hope of winning additional money and/or material goods.”

The most common gambling activity among those surveyed was scratch-off tickets, followed by bingo and lottery tickets. Of the respondents who reported gambling, around 20% said they had participated in sports betting. A smaller share said they bet in prediction markets (just over 6% of gamblers).

It’s been more than eight years since the Supreme Court issued the landmark ruling that struck down a federal law that prohibited states from allowing gambling on sports. The change touched off an explosion of betting across America.

Some form of sports gambling is now legal in 39 states and Washington, D.C. Mobile gambling apps, which include standard casino options and sports, have become particularly popular in recent years.

Baseball fans who watched the World Series over the last week were inundated with ads for prediction markets like Polymarket, Novig and Kalshi. The trading platform Webull occupied a spot on the Tampa Bay Rays uniform.

Nower said her findings “should be a wake-up call for parents, educators, health professionals and policymakers.”

“We cannot wait until young people reach adulthood to begin addressing gambling-related harm,” she said. “By that point, we will have very high rates of problem gambling. Prevention must start earlier, screening must be broader, and public policy must recognize that the gambling environment has changed dramatically.”