In some cases, compulsive gambling behavior can emerge as a side effect of medications. Mark Stacy, a neurologist at the Duke University School of Medicine in Durham, N.C., noticed that several of his Parkinson's disease patients began reporting gambling problems after he had increased their doses of drugs called dopamine agonists, used to treat motor dysfunction. As many as 10 to 15 percent of Parkinson's patients who take the drugs exhibit this tendency, he says. "I believe these drugs do cause gambling problems where they otherwise would not occur. When you stop the drug, the behavior goes away."

Foes of casino gambling say that the industry actively targets vulnerable older patrons. For every 20 older patrons who walk through their doors, says Les Berna national director of the advocacy organization Stop Predatory Gambling, the casinos want to "find a couple of them that they can take for all they're worth."

From social gambler to addict

Beauford Burton's experience at Harrah's Cherokee Casino is typical of such relationships.

In addition to sending birthday cards and weekly mailings with ticket deals to shows and vouchers for free play, the casino assigned a VIP host who called Burton at home to invite him back for various specials. Casino hosts often lavish personal attention on high-rolling older charges, asking about their health, reminding them to take their medicine and eating meals with them.

"The whole premise of a host is to extract as much money from that player as possible," says ex-host John-Talmage Mathis, who worked as VIP marketing director at the Boomtown Casino in Bossier City, La. "For older people, the host becomes their friend, giving them attention they may not be getting from their children or friends."

Casinos award hosts bonuses based on how much the gambler loses. "The losses of your player," Mathis says, "are your success."

As the industry seeks to expand, more women are being enticed into casinos, and more are experiencing problems, according to a study published in the journal Psychiatry.

Many slot machines are now designed specifically for women players, who, like longtime slots addict Melynda Litchfield, sometimes feel bonded with their machines. Litchfield, 56, worked 27 years at a Chicago-area hospital, climbing from staff nurse to administrator with a salary of $100,000.

Yet she couldn't afford a prom dress for her daughter because she lost so much playing slots at the Grand Victoria Casino in Elgin, Ill., 10 minutes from their home. For Litchfield, the atmosphere was as addicting as the machines themselves. The staff treated her warmly and called her by name. "They gave me so much personal attention and TLC that you get the false impression these people—who are milking away all of your money—actually care about you," she says.

The casino also served as an escape, to a place where she did not have to tend to the needs of anyone else. "I didn't want to talk to anyone," says Litchfield, who quit gambling in 2012 and is now a national victims advocate for Stop Predatory Gambling. "I just wanted to get lost in my machine."