Several years ago, doctors at the Mayo Clinic noticed something odd about some of their patients with Parkinson's disease. Soon after starting a type of medication to reduce symptoms, people who had rarely or never gambled couldn't stop. For example, a 68-year-old man who had never gambled began compulsively gambling—losing $200,000 in six months—after he started taking a drug called Mirapex. But he stopped gambling when he quit taking the medication.

The doctors' observations, published online this week in the Archives of Neurology, suggest that drugs in a class called dopamine agonists, which includes Mirapex, might be to blame for the behavior. The report, which describes an onset of pathological gambling in 11 patients after they took dopamine agonists, does not conclusively prove that the medications are associated with an increased propensity to gamble, but the authors write that the association was "striking." Previous studies have also linked dopamine agonists to compulsive gambling, though only in a small minority of cases.

Dopamine agonists work by mimicking the effects of the neurotransmitter dopamine, which helps people coordinate movement and influences how people experience reward and pleasure. Because Parkinson's results from a lack of dopamine in certain areas of the brain, these drugs can ease symptoms of Parkinson's, like tremors. However, at the same time, the drug affects people's impulsiveness and their need for the rush that dopamine can give in anticipation of a reward—such as winning at the slots.

Find out more: The National Parkinson's Foundation explains more about the disease and some of the treatment options.

Also check out U.S. News coverage of gambling addictions, which explains the role of dopamine.

Read the article: Dodd, M.L. et al, "Pathological Gambling Caused by Drugs Used to Treat Parkinson's Disease." Archives of Neurology. September 2005, Vol. 62. Published online July 11, 2005

Article online: archneur.ama-assn.org