Melatonin Metabolism Abnormality in Patients With Schizophrenia or Schizoaffective Disorder Treated With Olanzapine

In treatment phase I, all subjects will receive olanzapine, 10-25 mg/day. In treatment phase II, all subjects will receive olanzapine (10-25 mg/day) plus melatonin. Subjects will be randomized at a ratio of 1:1 to receive melatonin, 0.3 mg/day or 3.0 mg/day. Group IIA will receive 0.3mg day melatonin. Group IIB will receive 3.0 mg/day melatonin.