The main purpose of this study is to follow and observe a group of people living with Parkinson's disease to see how study participation affects their signs and symptoms in the months after starting in the study. While taking part in this study participants will take their usual medication as prescribed. However, the study doctor may recommend adjustments to their medication to provide a better treatment of their Parkinson's disease. Participation will last from 3 up to 24 months. During visits to the clinic, the study doctor or study nurse will evaluate signs and symptoms of Parkinson's disease using several different assessments. At a minimum of 2 visits participants will be asked to undergo 'off'-assessments.