We have long known that constipation is a common non-motor feature of Parkinson disease (PD) (1). One study of 7000 men over a period of 24 years showed that those with initial constipation (less than one bowel movement per day) had a three-fold risk of PD after an average of 10 years (2).  Thus, unexplained … Continue reading What is the Gut-Brain Axis?