Extract of Ginkgo Biloba and Tardive Dyskinesia

Inclusion Criteria: * Male or female aged 18 to 60yrs * Meeting Diagnostic and Statistical Manual of Mental Diseases, Fourth Edition(DSM-IV) criteria for schizophrenia or schizo-affective disorder * Abnormal Involuntary Movement Scale (AIMS) score ≥2. * Patients from whom informed, written consent is obtained. * Patients who have been on a fixed dose of antipsychotic medication for at least 4 weeks prior to trial entry. Exclusion Criteria: * Significant neurological disorder other than TD * Substance abuse * Significant other medical illness * Psychiatric disorder not stabilised * Pregnancy or lactation * Take antioxidants(such as Vitamin C)