Parkinson’s disease (PD) occurs when brain cells that make dopamine, a chemical that coordinates movement, stop working or die. Because PD can cause tremor, slowness, stiffness, and walking and balance problems, it is called a “movement disorder.” But constipation, depression, memory problems and other non-movement symptoms also can be part of Parkinson’s. PD is a lifelong and progressive disease, which means that symptoms slowly worsen over time. The experience of living with Parkinson's over the course of a lifetime is unique to each person. As symptoms and progression vary from person to person, neither you nor your doctor can predict which symptoms you will get, when you will get them or how severe they will be. Even though broad paths of similarity are observed among individuals with PD as the disease progresses, there is no guarantee you will experience what you see in others. Estimates suggest that Parkinson’s affects nearly 1 million people in the United States and more than 6 million people worldwide. https://www.michaeljfox.org/parkinsons-101