Parkinson's disease in the elderly: psychiatric manifestations.

Drug-induced psychiatric symptoms are usually reversible within days. However, if the patient also has cognitive impairment of a more permanent nature, improvement may not be seen for weeks or even months. During the year preceding the diagnosis of Parkinson's disease, the incidence of depression, hyperirritability, and instability of emotions is significant. After the onset of Parkinson's disease, depression is very common.