"These results provide further evidence that impulse control disorders that occur in people with Parkinson's disease are related to the exposure to the dopamine-related drugs, not just the disease itself," Weintraub said. "More long-term studies are needed to determine if the 20 percent of people who have some symptoms of these disorders are more likely to develop impulse control disorders once they start treatment for Parkinson's."
According to Niethammer, the new study "adds to the growing body of evidence that such impulse control disorders relate to treatment and are not an intrinsic feature of Parkinson's disease."
That means that should such behaviors arise, "they are most likely related to treatment, and the medications may need to be changed or stopped if possible," he added.
Another expert said the study brings up intriguing issues.
"An interesting question is whether susceptibility to impulse control disorders development on Parkinson's disease medication is due to Parkinson disease, or other risk factors such as genetics," said Dr. Kely Changizi, co-director of the Center for Neuromodulation at th Mount Sinai Medical Center in New York City. "That is, if healthy people were given high doses of dopamine agonists, would they develop impulse control disorders at the same rate as people with Parkinson's?"
According to Changizi, "we do know that patients with restless leg syndrome, who do not have Parkinson's disease, can develop impulse control disorders when treated with higher dose dopamine agonists [a form of Parkinson's drug]. This paper is an interesting contribution to the field of movement disorders, and sheds light on former controversy."
While the study showed an association between Parkinson's medications and compulsive behaviors, it did not prove a cause-and-effect relationship.
The study was partially supported by drug makers Abbott, Biogen Idec., F. Hoffman-La Roche Ltd., G
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