The Therapeutic Effect of Transcranial Direct Current Stimulation on Depression in Parkinson's Disease

Parkinson's disease (PD) is one of the most common neurological diseases manifested by movement disturbance. The concomitant psychiatric symptoms, especially depression, are often observed and have also great impact on patients' quality of life. The treatment of depressive symptoms in PD with antidepressants as the majority remains variable and inefficient, which complicates the disease prognosis. Transcranial direct current stimulation (tDCS) is a non-invasive brain modulation technique and has been demonstrated to improve psychiatric diseases such as major depression. In this study the investigators will assess the combined effects of tDCS on sertraline for the treatment of depression in PD. Ten sessions of tDCS in two weeks will be applied and the follow-up evaluation will continue bi-weekly for one month after completing all sessions. The efficacy of tDCS vs sertraline will be compared and evaluated with behavioral and cognitive outcome. In addition, the investigators will evaluate if the baseline dopaminergic activity in brain could predict the treatment outcome by using SPECT imaging. The investigators aim to establish the therapeutic parameters and safety criteria of tDCS as an add-on or alternative therapy, and further enhance the overall clinical efficacy in the treatment of depression in PD.