Which Parkinson's Patients Will Feel the Urge to Gamble?
It's been known for some time that taking dopamine agonists to treat Parkinson's disease may have an unintended consequence: the overwhelming urge to gamble. In a new study, researchers pinpoint the characteristics that may make people vulnerable. Writing in the current Archives of Neurology, they report that patients who are younger at diagnosis (an average of 60, compared with 66 in the control group), who have a personal or family history of alcohol abuse, and who tend to seek out novelty are most susceptible to gambling problems when taking the drugs.
The drugs act like the neurotransmitter dopamine–which among other things sends signals between brain cells responsible for movement and is deficient in Parkinson's patients–and thus help regulate the tremors and other symptoms of the disease. But since dopamine is also involved in how the brain reinforces certain activities with feelings of pleasure, the medications can bring on behaviors like binge eating and compulsive sexual behavior or gambling.
Researchers looked at 21 Parkinson's patients who developed pathological gambling after receiving a dopamine agonist and compared them with 42 Parkinson's patients who didn't experience gambling or any other compulsive behaviors. Those qualities emerged as the differences between the groups. Previous research by some of the same researchers showed that 7.2 percent of Parkinson's patients taking dopamine agonists developed pathological gambling, more than twice the 3.4 percent of patients who started gambling but were not taking the drugs.
These problems may not be limited to Parkinson's patients. The same group of drugs is also used to treat restless legs syndrome, a collection of symptoms (including the urge to move one's legs when lying down) that in the past few years has increasingly been characterized as a disease requiring drug treatment. (Sales of Requip, the dopamine agonist approved for restless legs as well as Parkinson's, rose 76 percent to about $520 million in 2006.)
Last month, researchers at the Mayo Clinic reported that three patients with no history of gambling problems being treated for restless legs syndrome developed pathological gambling behavior. (Two lost more than $100,000.) The dose for restless legs is lower than that for Parkinson's, and the medication is taken at night only, so fewer people may develop compulsive behavior, says Valerie Voon, lead author of the Parkinson's study and researcher at the National Institute of Neurological Disorders and Stroke at the National Institutes of Health. But larger studies are necessary to determine how common these problems are in that population.
In the meantime, she and the Mayo researchers urge doctors to be aware of the potential for compulsive behavior and to warn their patients to be vigilant for signs of problems. If necessary, they can be switched to other medications.