Early Intervention of Prodromal Schizophrenia Using an NMDA Enhancer

Inclusion Criteria: * Individuals meeting Criteria of Prodromal Syndrome (at least one of the following: 1. attenuated positive symptoms; 2. brief intermittent psychotic symptoms; 3. genetic risk and deterioration). * Subjects remain symptomatic (scoring at least 20 on the Scale of Prodromal Symptoms \[SOPS\] total score) after the 6-week screening phase (which contains the health-promotion program) and before the 12-week drug-trial period. * Subjects may be receiving ongoing treatment with antipsychotic medications, or may be medication-free for at least 12 weeks.For the subjects who have already been on such medications, the medications need to be continued for at least 4 weeks before the screening phase and the doses need to be kept unchanged during the study period. For those who have not yet been on such medications, these medications are forbidden during the study period. * Subjects agree to participate in the study and provide written informed consent after complete description of the study. For the subject \< 20 years old, a parent also has to provide written informed consent. Exclusion Criteria: * DSM-5 diagnosis of intellectual disability, substance (including alcohol) use disorder, schizophrenia, schizophreniform disorder, delusional disorder, schizoaffective disorder, substance/medication-induced psychotic disorder, or psychotic disorder due to another medical condition. * History of epilepsy, head trauma, stroke, or serious medical or central nervous system diseases (other than schizophrenia) which may interfere with the study. * Clinically significant laboratory screening tests (including blood routine, biochemical tests) * Pregnancy or lactation * Inability to follow protocol