Background: A variety of neuropsychiatric symptoms commonly occur in Parkinson's disease. Extensive research the last 10 years has provided new knowledge in the field.
Material and methods: This review is based on literature retrieved from a Medline search and own research and clinical experience.
Results and interpretation: Neuropsychiatric symptoms occur in the majority of patients with Parkinson's disease, and are associated with impaired quality of life for patients and relatives, additional deterioration of function and increased use of health resources. Medical and surgical therapies can induce or worsen such symptoms. Cognitive impairment and dementia are among the most common and severe complications to Parkinson's disease. No disease-modifying treatment is available, but rivastigmine was effective in one large randomised trial. Visual hallucinations are common and often persistent, but can be treated with klozapin if reducing the number and dose of antiparkinson agents are not helpful. Depression occurs frequently, usually mild, but there is little evidence of treatment efficacy. Apathy, anxiety and sleep disturbances are additional commonly occurring neuropsychiatric symptoms. Neuropsychiatric symptoms are so frequent in Parkinson's disease that they should be considered an integral part of the disease; it is important that clinicians are aware of these symptoms.