Neuropsychiatric aspects of Parkinson's disease.

Throughout the natural history of Parkinson's Disease (PD), from the pre-diagnostic phase to end stage disease, neuropsychiatric manifestations represent a core feature of the disease. This review summarises current knowledge on the features of depression, anxiety, apathy, fatigue, impulse control disorders (ICDs) and psychosis in PD. These co-morbidities are common and still frequently under-recognised. Their impact on quality of life is considerable, with depression having been shown to be the main determinant of health-related quality of life in PD patients. As well as formal diagnostic criteria, multiple scales have been developed to allow for assessment of these symptoms in both the clinic and research settings. The evidence base for treatment is variable, with increasing evidence for pharmacological and non-pharmacological treatment options for depression, but less robust evidence for the treatment of other neuropsychiatric features. Imaging studies are increasingly providing insight into the neural basis of these symptoms, with the hope that this insight will translate into treatments that can benefit patients.