Cognitive and psychiatric disturbances in Parkinson’s disease

Psychiatric symptoms and cognitive impairment occur in the majority of patients with Parkinson’s disease and have important clinical consequences for the patient and caregivers, in addition to health-related costs. Dysphoria and anxiety, hallucinations, apathy and cognitive impairment are the most common symptoms. The etiology is heterogeneous and includes psychosocial, structural and chemical brain changes, and treatment-related factors. Consensus criteria for the diagnoses of psychosis, depression and dementia associated with Parkinson’s disease are now available, and a number of rating scales and questionnaires have been validated for the evaluation of cognitive impairment and psychiatric symptoms in Parkinson’s disease. Level I evidence is available for the treatment of dementia, depression and psychosis, but there is still a need for development of safer and more effective treatments.