The aim of this open-label, self-control study is to evaluate the efficacy of sertraline in treating depression in Patients with Parkinson's disease. In addition, the investigators also want to find out whether patient gets better quality of life when depression is improved.

Depression in PD is associated with more severe cognitive and functional impairments, a faster progression of illness, worse quality of life, increase mortality and higher burden for caregivers, when compare PD patients without depression. Depression accounts for approximately 40-50% in PD patients, which is also well known as a main factor impacting on health-related quality of life (HRQoL) in negative way in the context of PD and even their caregivers. In our previous cross-sectional study, the investigators have already studied the prevalence of depressive symptoms in PD patients and also have proved how depressive symptoms severely worsen HRQoL in PD patients in the area of the mainland China. In order to improve HRQoL of PD, some interventions, for example, taking some antidepressants to improve depression are urgently required. In addition, the investigators had already tested the validity and reliability of Chinese version of the 39-item Parkinson's disease questionnaire (PDQ-39) in mainland China, the paper about which already have been published in journal of Zhejiang university science B (biomedicine and biotechnology) already, therefore, the investigators can use the questionnaire of Chinese version of PDQ-39 to assess PD patients' quality of life.

Treatment of depression with antidepressant drugs is well established. In the last 20 years, the application of antidepressant has risen mainly due to the introduction of the selective serotonin reuptake inhibitors (SSRIs). These drugs are now the most commonly prescribed antidepressants in patients with depression in general. Regarding depression in the context of PD, a recent survey in the U.S. showed that 63% of the prescriptions for depression in PD were for SSRIs and only 7.5% for tricyclic antidepressants (TCAs). The preference of SSRIs over the older TCAs is supposedly based on their similar efficacy but better tolerability, especially when compared with tertiary amines, such as amitriptyline or imipramine. Sertraline is characterized by a low selectivity for serotonin relative to dopamine reuptake, suggesting a favorable efficacy profile. There was a randomized study pointing out that both sertraline and low-dose amitriptyline improved depressive symptoms in PD, and a significant benefit on quality of life was observed only with sertraline. Still, more studies are needed to demonstrate whether sertraline is effective to depression in PD patients. Further more, there is no trial about the efficacy and safety of sertraline on depression in PD in mainland China. It's necessary for us to initiate and conduct this trial in mainland China.

Inclusion Criteria:

1. Patients between 35 and 75 years of age from the outpatients clinic in Department of Neurology, the Second Affiliated Hospital, School of Medicine, Zhejiang University.
2. All patients should have a confirmed diagnosis of PD according to Brain Bank Criteria.
3. Diagnosed to be major depression episode according to DSM-IV,
4. Mini Mental State Examination (MMSE) exclude dementia.

Exclusion Criteria:

1. Mini-Mental State Examination (MMSE) demonstrate dementia
2. Any current DSM-IV Axis I diagnosis other than a depressive or anxiety disorder.
3. History of psychosis or hallucinations or under treatment with atypical neuroleptics.
4. Treatment-resistant depression. Treatment-resistant depression (TRD) occurs when a patient with unipolar depression fails to respond to adequate antidepressant therapy.
5. Pregnancy or lactation.
6. Concomitant use in patients taking monoamine oxidase inhibitors (MAOIs).
7. Concomitant use in patients taking pimozide.

Adverse event data were collected for each visit from administration to endpoint.