Saul Malek grew up surrounded by sports.

He played soccer and Little League, and shot hoops at the neighborhood court. He was obsessed with the Houston Astros. When they won, he was ecstatic. Once when they lost, he whipped a belt at a wall so hard he chipped the paint.

Malek joined a fantasy baseball league while in middle school. In college, an acquaintance connected him with a bookie. Winning his first bet — $10 that the Royals would beat the Blue Jays — made him feel “like a big shot,” he said.

But he soon found that he needed “nonstop action.” He would find an online sportsbook and maybe win enough to pay a former bookie back. More often, though, he’d lose. Then he would block the bookie’s number, find a new sportsbook and repeat.

His parents bailed him out for hundreds of dollars several times, but he didn’t seek help until he “felt physically uncomfortable” one night after not placing a bet in time. He realized he didn’t have any close relationships left.

Malek, now 23 and living in Houston, said he had never considered that sports betting could escalate to an addiction that would lead him to lie, cheat and manipulate people for money. And yet he has come to have plenty of company as policy shifts and technological advances have made it easier than ever to wager money on sports.

Analysts and recovery advocates worry that efforts to research the long-term implications of legal sports betting and warn participants about the risks for addiction are falling short, particularly for people in their late teens and early 20s who are most vulnerable.

“We’re now in a phase where the nation has an appetite for sports betting,” said Timothy Fong, a professor of psychiatry with specialty in addiction at the University of California, Los Angeles. “It’s created this new form of entertainment that society has approved, but that form of entertainment does have a potential for addiction.”

Long restricted to Nevada, sports betting expanded rapidly after the Supreme Court overturned federal prohibitions against it in 2018. It is now legal in 21 states and Washington, D.C. In many states, people can legally and conveniently wager money using their smartphones, betting on point spreads or results, or placing so-called proposition bets on events like the coin toss or which color of Gatorade will be dumped on the winning coach.

Americans wagered $13 billion on sports with legal operators in 2019, according to the American Gaming Association, the industry’s trade group, with popular events like the Super Bowl whipping bettors into a frenzy. The Gaming Association expects 47 million Americans to place bets on the NCAA “March Madness” basketball tournaments, which reach a climax with the Final Four stage for the women on Friday and the men on Saturday.

Most adults who bet on sports do so without major negative consequences. But about 1% of American adults have a gambling disorder, in which the core symptom is continuing to gamble despite harmful consequences, said Fong, who is a director of the Gambling Studies Program at UCLA.

A vast majority of those with a serious gambling problem never seek or gain access to treatment, he said.

Studies have shown that sports bettors are typically male, under 35, single, educated and employed or preparing for a career. According to a new survey commissioned by the National Council on Problem Gambling, sports bettors showed significantly higher levels of problematic gambling than other gamblers. The risk of addiction is higher for young adults — specifically sports bettors — than for those of any other age, the survey found.

According to CollegeGambling.org, a subgroup of the International Center for Responsible Gaming, 6% of college students in the United States have a serious gambling problem that can lead to psychological difficulties, unmanageable debt and failing grades.

Young adults are at particular risk for developing a gambling problem, especially if there is a family history of gambling or if they are introduced to it at a young age, Fong said. The increased accessibility of online gambling may accelerate the development of problems, he said — a phenomenon known as telescoping.

As sports betting has grown — household names like FanDuel and DraftKings now offer legal avenues — the need for recovery programs and dedicated treatment facilities has quickly outpaced their availability, recovery experts said. Rick Benson, the founder of the Algamus Gambling Recovery Center in Arizona, said the number of young adults who have sought treatment for gambling problems has more than doubled in the past two years.

Sex, drugs and alcohol are commonly covered in school and in the coming-of-age conversations that parents have with their children, but discussions about the consequences of gambling are rare, former gamblers and experts said. This can lead young people to underestimate the addictive nature of sports betting and other forms of gambling. Warnings, often in small fonts, that caution visitors to online sportsbooks and gambling websites about the risks of addiction are easily overlooked.

“You can do it 24/7 from right on your phone,” said one recovered gambling addict, a 38-year-old man who spoke on the condition of anonymity because he was about to embark on a job search.

“It’s really, really dangerous,” he said, noting he had contacted a few websites during his recovery and asked to be blocked, but they had allowed him to reopen his accounts after he relapsed.

Over the last 30 years in the United States, there has been a shift in the cultural perception of gambling, said Keith Whyte, director of the National Council on Problem Gambling, a research and advocacy group. Once viewed as a vice, sports betting in particular has become more widely accepted as a form of entertainment and as a new source of tax revenue for the states that have legalized it, he said.

“It’s now become a positive element of state, financial or economic policy. But it’s also addictive, and therein lies the rub,” said Whyte, whose organization is neutral on the legalization of gambling. “It’s the only addictive service or product where a state government is so heavily involved.”

But when people become addicted, the blame often falls on the individual rather than on an industry whose advertising and marketing, including bonuses and risk-free trials, are targeted to young men.

More than half of adults surveyed by the National Council on Problem Gambling attributed gambling problems “at least in part to moral weakness or lack of willpower,” and fewer than half said they believed a medical or a genetic condition played a role. Half of those surveyed said “people with a gambling problem are to blame for their problems.”

“It’s still seen as a moral failing rather than a medical disorder,” Whyte said. “Americans have made that connection with drugs and alcohol, but they haven’t made that connection yet for gambling.”

According to the American Gaming Association, $4.4 billion was wagered with legal sportsbooks across the country in January, the sixth consecutive month in which a “national handle record” was broken. The association found that legal U.S. operators took in nearly $908.9 million in sports betting revenue from more than $13 billion in wagers in 2019, more than double the $430.7 million in revenue they collected in 2018.

The states that authorized gambling on sports as a new source of revenue and jobs “are also the ones who are supposed to be protecting their citizens from the adverse effects they’re talking about,” Whyte said. “They’re supposed to be balancing the costs and benefits.”

Many young adults have embraced gambling and sports betting as new social traditions. There are March Madness brackets, poker nights and casino fundraisers for fraternities and sororities.

“It’s just so accepted, so acceptable, it makes it just so easy to get involved with,” Malek said. “It’s advertised as a normal part of being, like, a 20-year-old guy: Make some money, make some sports bets, make your fantasy team — whatever. It’s just cool.”

Malek said his struggle with addiction motivated him to pursue a master’s degree in clinical mental health counseling at Southern Methodist University in Dallas. He discusses his addiction openly with the hope that doing so will sound an alarm about how quickly and easily dabbling in sports betting can lead to disaster.

He recalled the older participants in the 12-step program he completed sharing stories of reading the newspaper to find out the scores of games from the night before, and calling their bookies on the phone.

“I think that the industry of sports betting is definitely evolving, which is scary for the public,” Malek said. “You’re always clicks away from it anytime you want it. It’s out there 24/7. I don’t think that people are aware of how devastating the consequences of this will be.”