(HealthDay News) – For patients with Parkinson’s disease, of all the factors affecting the course of the disease, depression and anxiety have the biggest impact on health status, according to early findings from the largest ongoing study of Parkinson’s disease, published online Nov. 28 by the National Parkinson Foundation.

John Nutt, MD, from the Oregon Health & Science University in Portland, and colleagues from the Parkinson’s Outcomes Project examined data from more than 5,500 individuals with Parkinson’s disease in the United States (85% of patients), Canada, Israel, and the Netherlands, to identify and assess factors associated with better outcomes. Data were collected through annual questionnaires and related to a range of factors, including medication and other treatment use, motor symptoms, cognition, anxiety and depression, and caregiver burden.

The researchers identified considerable variation in care, even among leading treatment centers. The variations included different outcomes for similar patients depending on their treatment center; different use of medications between centers and neurologists; and different rates of referral to therapists. Depression and anxiety were found to have the greatest impact on health status, with at least 50% of participants experiencing depression.

“Routine aspects of care are rarely studied, so this research is invaluable in proving that there are vast disparities in Parkinson’s treatment and showing which aspects of care really work,” Matthew Stern, MD, the president-elect of the Movement Disorder Society, said in a statement. “For example, this latest data [demonstrate] how important it is to quality care to refer patients for multi-faceted treatment of depression.”

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