NMDA-enhancing Treatment for Cognitive Dysfunction of Schizophrenia

Inclusion Criteria: * Have a Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5 -TR) diagnosis of schizophrenia * Fulfill the Remission in Schizophrenia Working Group (RSWG) criteria for remission (Andreasen et al., 2005): each of eight items (delusions, unusual thought content, hallucinatory behavior, conceptual disorganization, mannerisms/posturing, blunted affect, passive/apathetic social withdrawal, and lack of spontaneity and flow of conversation) in the Positive and Negative Syndrome Scale (PANSS) (Kay et al., 1987) scoring 3 or lower for 6 months or longer; in addition, have a baseline total score of 59 or lower in the PANSS * Are physically healthy and laboratory assessments (including blood routine, biochemical tests) are clinically insignificant; * Have been keeping a fixed dose of antipsychotics (excluding clozapine) for at least 6 months, and that is not allowed to change during the 12-week study period * Have sufficient education to communicate effectively and are capable of completing the assessments of the study * Agree to participate in the study and provide written informed consent Exclusion Criteria: * DSM-5-TR diagnosis of intellectual disability or substance (including alcohol) use disorder * History of epilepsy, head trauma, or serious medical or central nervous system diseases (other than schizophrenia) which may interfere with the study * Pregnancy or lactation * Inability to follow protocol