In addition to motor symptoms, non-motor symptoms including clinically significant anxiety and depression are common in PD, affecting approximately 30-40% of PD patients (Doder et al., 2005; Weintraub et al., 2005; Schulman et al., 2001; Menza et al., 1993)
Health-related quality of life, including mood related symptoms tend to worsen over the course of the disease (Karlsen et al., 2000)