Metformin Treatment on Cognitive Impairment of Schizophrenia

Participants screened through inclusion and exclusion criteria will be randomized to metformin or placebo group (2:1). The information of demographic data, medical history, previous and current medication regimen, and family history regarding psychotic and metabolic diseases will be collected at baseline. The assessments will be carried out at baseline, 12th week and 24th week, including physical examination, anthropometry, blood test(blood routine, liver function, renal function, blood lipids, fasting blood glucose, serum insulin and thyroid function), electrocardiogram, MRI scan( High-resolution T1-weighted Anatomical Images, Diffusion Tensor Imaging, Resting-state functional MRI and Arterial Spin Labeling) and psychiatry scales(Positive And Negative Syndrome Scale, Scale for Assessment of Negative Symptoms, Calgary Depressing Scale for Schizophrenia, Personal and Social Performance Scale, The Systematic Assessment for Treatment Emergent Events, the Simpson-Angus Extrapyramidal Side Effects Scale and the Barnes Akathisia Rating Scale); cognitive function will be assessed by the Measurement and Treatment Research to Improve Cognition in Schizophrenia(MATRICS) Consensus Cognitive Battery; biological samples also will be collected and stored to explore related mechanisms. Participants who don't meet any of the diagnostic criteria for metabolic syndrome will only accept baseline evaluations. In addition, we will recruit healthy volunteers, and collect their demographic data, and family history regarding psychotic and metabolic diseases. Apart from psychiatry scales(Hamilton Depression Scale, Young Mania Rating Scale and Self-reporting Inventory-90), other assessments for the healthy subjects are the same as the baseline for sczhiophrenic participants.