We will evaluate the effect of deep brain stimulation on the depression and quality of life in Parkinson's disease. We aim to compare depression pre-operatively and post-operatively in Parkinson's patients with deep brain stimulation to Parkinson's patients evaluated and approved for deep brain stimulation but who did not complete surgery. We will also compare quality of life measures between patients with and without deep brain stimulation.

Deep brain stimulation is an approved therapy for Parkinson's patients, and this procedure is actively performed at Vanderbilt University Hospital. Questions have been raised concerning the effect of deep brain stimulation on the depression commonly seen in Parkinson's patients. Through this study, we plan to evaluate and compare the incidence and severity of depression in Parkinson's patients with deep brain stimulation to those who did not complete the surgery. Primary literature has indicated a general increase in quality of life of those patients receiving DBS, but no studies have compared these two specific patient populations.

Inclusion Criteria:

• Patients diagnosed with idiopathic Parkinson's disease.
• Patients who have received neuropsychological testing in preparation for possible deep brain stimulation.
• Patients are within the age of 50 and 85.

Exclusion Criteria:

• Parkinson's patients not approved for deep brain stimulation on the basis of neuropsychological testing.
• Patients who received deep brain stimulation less than a year ago.
• Patients who do not consent to the study procedures.