CHICAGO, July 11 - Joe Neglia was a retired government intelligence worker with Parkinson's disease when he suddenly developed a troublesome gambling habit.

After losing thousands of dollars playing slot machines near his California home several times a day for nearly two years, Mr. Neglia says he stumbled across an Internet report linking a popular Parkinson's drug he used with compulsive gambling.

"I thought, 'Oh my God, this must be it,"' he said. Three days after stopping the drug, Mirapex, "all desire to gamble just went away completely."

"I felt like I had my brain back," he continued.

A Mayo Clinic study published yesterday in July's Archives of Neurology describes 11 other Parkinson's patients who developed the problem while taking drugs for the disease from 2002 to 2004. Doctors have since identified 14 additional Mayo patients with the problem, said Dr. Maryellen Leann Dodd, a Mayo psychiatrist who was the lead author of the study.