Neuropsychiatric symptoms and cognitive abilities over the initial quinquennium of Parkinson Disease.

Weintraub D, Caspell-Garcia C, Simuni T, Cho HR, Coffey CS, Aarsland D, Alcalay RN, Barrett MJ, Chahine LM, Eber;omg J, Espay AJ, Hamilton J, Hawkins KA, Leverenz J, Litvan I, Richard I, Rosenthal LS, Siderowf A, York on behalf of the Parkinson's Progression Markers Initiative.