Neuropsychiatric symptoms in Parkinson's disease: aetiology, diagnosis and treatment

Historically, Parkinson's disease was viewed as a motor disorder and it is only in recent years that the spectrum of non-motor disorders associated with the condition has been fully recognised. There is a broad scope of neuropsychiatric manifestations, including depression, anxiety, apathy, psychosis and cognitive impairment. Patients are more predisposed to delirium, and Parkinson's disease treatments give rise to specific syndromes, including impulse control disorders, dopamine agonist withdrawal syndrome and dopamine dysregulation syndrome. This article gives a broad overview of the spectrum of these conditions, describes the association with severity of Parkinson's disease and the degree to which dopaminergic degeneration and/or treatment influence symptoms. We highlight useful assessment scales that inform diagnosis and current treatment strategies to ameliorate these troublesome symptoms, which frequently negatively affect quality of life.