Diagnoses of gambling disorder have climbed sharply in states that legalized sports betting since the Supreme Court's 2018 decision cleared the way for widespread online wagering, according to a recent study that is renewing concerns about the industry's rapid expansion.

Epic Research found gambling disorder diagnoses jumped more than 60% in states with legal sports betting, while diagnoses declined in the 11 states that have not legalized the practice.

The study reviewed electronic health records from more than 197 million U.S. adults between January 2018 and March 2026. Diagnoses in states with legalized sports betting increased from 3.0 cases per 100,000 adults to 4.8 per 100,000, while cases in states without legalized sports betting fell by about 30%.

Young adults saw the steepest increase. Adults ages 18 to 29 — particularly men — experienced the largest jump in gambling disorder diagnoses, while adults ages 30 to 49 had the highest overall rate.

Epic Research said the findings "cannot be attributed to any single legal event," pointing to factors such as expanded telehealth, increased clinician awareness, and changes in diagnostic coding. Even so, researchers said the trend is consistent with other studies showing more people are seeking help for gambling problems in states that legalized sports betting.

"You increase access, you increase problems," Rutgers University social work professor Mark van der Maas told NBC News.

"As soon as you introduce a new form of gambling or dramatically increase the availability of gambling, you will be increasing the number of people that are experiencing harm because of that gambling," he added.

Harry Levant, director of gambling policy at the Public Health Advocacy Institute, argued that the findings underscore the risks of online gambling platforms.

"This is extremely important evidence that speaks to not only the impact of legalization — but the inherently dangerous nature of how online gambling is fundamentally different than anything we've seen before," Levant told NBC. "You're introducing younger and more vulnerable people to a highly addictive product."

The American Gaming Association pushed back, saying the study reflects increased screening and awareness rather than rising addiction rates.

"While problem gambling is a serious condition for those impacted, this study does not indicate an increasing rate of addiction," the group said in a statement. "Increased screening and greater awareness of available resources can often lead to more diagnoses, while decades of research have found no increase in problem gambling rates as legal gaming has expanded."

Clinicians who treat gambling addiction say they are seeing more people walk through their doors.

"We've seen definitely an increase in related referrals and diagnoses," Steven Heim, outpatient supervisor at New Hope Integrated Behavioral Health Care in New Jersey, told NBC.

Experts also warned the study likely understates the scope of the problem because many people never seek treatment.

Rachel Volberg, a longtime gambling researcher, told the outlet, "Typically, no more than 3% to 10% of people who would be diagnosed with disordered gambling actually access treatment services for a gambling problem."

Former New Jersey Attorney General Matthew Platkin predicted the consequences of legalized online sports betting will become more apparent over time.

"It's going to take a few years for us to recognize these harms because it doesn't show up on day one," Platkin told NBC. "It takes a while for problematic gambling behaviors to appear, and I will bet anything that three years from now, we're going to see a spike."