Psychiatric symptoms in Parkinson's disease.

Aside from the well-known triad of resting tremor, postural instability, and bradykinesia, Parkinson's disease (PD) patients may also develop psychiatric illness as a part of their disease. The psychiatric symptoms may be as disabling as the movement disorder, but are often amenable to treatment. We review the most recent investigations of mood disorders, anxiety disorders, and hallucinations/ psychosis in PD. We then highlight new treatment studies for hallucinations/psychosis in PD.