D-Serine Treatment For Tardive Dyskinesia

Inclusion Criteria: 1. age 18-70; 2. diagnosis of schizophrenia/schizoaffective disorder according to DSM-IV criteria; diagnosis will be made on the basis of SCID interview and information from medical records, previous treating psychiatrists, and family informants; 3. history of ≥3 months antipsychotic drugs treatment and present stable dose antipsychotic treatment for at last 4 weeks; 4. fulfillment of Schooler-Kane TD research criteria on a first evaluation performed 2-12 weeks prior to study entrance and on a subsequent evaluation performed prior to allocation to experimental treatment. Exclusion Criteria: 1. meeting criteria for other DSM-IV Axis I diagnoses; 2. presence of a neurological disorder or history of significant head injury; 3. substance abuse or alcoholism during entire lifetime; 4. are judged clinically to be at suicidal or homicidal risk; 5. female patients who are pregnant or lactating; female patients who are not pregnant or lactating, if sexually active, must be using medically accepted means of contraception.