Weintraub is the senior author of a study published this month in the journal Neurology. Using data from the Parkinson's Progression Markers Initiative - a multicenter effort funded by the Michael J. Fox Foundation and pharmaceutical companies - Weintraub's team studied patients from diagnosis to two years later. The database included 423 newly diagnosed Parkinson's patients, but only 96 who had been followed for two years.
The study found that the Parkinson's patients were disproportionately likely to have depression, anxiety, and apathy when diagnosed and throughout the two-year period. Those who took drugs that increased the level of the neurotransmitter dopamine, commonly used to treat the disease, had a higher risk for impulse-control problems and sleepiness.
Weintraub, who worked with researchers from the Philadelphia VA Medical Center and University Hospital Donostia in Spain, said other studies have connected the medications with impulse problems - Parkinson's patients are known to be at risk for compulsive gambling or spending - but this was the first to show that impulsiveness increased after treatment began.
None of the untreated patients developed impulse-control problems, compared with 17 percent of the treated patients. The study did not look at whether the 21 percent of patients who initially screened positive for impulse-control issues got worse on medication.
Apathy and psychosis worsened over time.
While the medications seemed to increase sleepiness, they also helped fatigue. Weintraub said researchers didn't yet understand that.
He does not recommend against using the dopamine-replacement drugs.
His primary message is that doctors should be alert for psychiatric problems in Parkinson's patients. Even though antidepressants and cognitive behavioral therapy have been proved to help this group, most of the depressed patients in the study were not taking anything for their symptoms.
The suicide of Robin Williams, whose wife said he had recently been diagnosed with Parkinson's, brought extra attention to mental-health consequences of the disease. A 2008 study Weintraub conducted found that thinking about death and suicide was common in an elderly group of Parkinson's patients, but that actual suicide was no more common than in the general population.
He thinks that Williams' complex medical and psychological history could have supplied many reasons for depression.
Parkinson's is a sobering, life-altering diagnosis that presents a legitimate emotional challenge. Weintraub said he could honestly tell patients that, for many, symptoms were mild and progressed slowly. It is more rapid for others. Eighty percent eventually develop dementia.
"It is a difficult illness, no doubt," he said, "and you can't hide that from people."