This study will recruit depressed patients unresponsive to selective serotonin reuptake inhibitor antidepressant treatment, first-degree relatives (parents or siblings) of depressed patients, schizophrenia, Parkinson's disease with and without depression, and healthy controls. The subjects need to complete the brain positron emission tomography/magnetic resonance examination, stress assessment, genetic testing, clinical evaluation and neuropsychological tests. Using the data, this study aimed to identify the abnormalities of reward circuit of depression and its differences with other diseases, and its abnormalities in first-degree relatives of depression. The depressed patients who were ineffective in treatment with selective serotonin reuptake inhibitor antidepressants were then given combined medication with dopamine receptor-mediated drugs, including dopamine transporter inhibitor - bupropion, D2 receptor antagonist - risperidone, or D2 receptor partial agonist - aripiprazole, to examine the regulation of dopamine pathway and its relationship with the therapeutic effect. Through the above work, we will provide new evidence for integrating the biological evidence of dopamine reward pathway into the clinical practice of depression.

Inclusion Criteria:

• patients unresponsive to SSRI antidepressant treatment, first-degree relatives (parents or siblings) of depressed patients, schizophrenia, Parkinson's disease with and without depression, and healthy controls

Exclusion Criteria:

• Major physical illness; other DSM-IV axis I mental illness; personality disorder, mental retardation; drug and/or alcohol dependence; pregnant or lactating women; MRI examination contraindications.