Effectiveness of Tropisetron Plus Risperidone for Improving Cognitive and Perceptual Disturbances in Schizophrenia

Inclusion Criteria: * Currently resides in Beijing, China * Diagnosis of schizophrenia or schizophreniform disorder * Duration of symptoms is no longer than 60 months * No history of treatment with antipsychotic medication or, if previously treated, a total lifetime usage of less than 14 days * Current psychotic symptoms are of moderate severity or greater as measured by one of the five psychotic items in the Brief Psychiatric Rating Scale (BPRS) Exclusion Criteria: * Diagnostic and Statistical Manual of Mental Disorders(DSM)-IV Axis I diagnosis other than schizophrenia or schizophreniform psychosis * Documented disease of the central nervous system that might interfere with the trial assessments (e.g., stroke, tumor, Parkinson's disease, Huntington's disease, seizure disorder, history of brain trauma resulting in significant impairment, chronic infection) * Acute, unstable, and/or significant and untreated medical illness (e.g., infection, unstable diabetes, uncontrolled hypertension) * A clinically significant echocardiogram (ECG) abnormality in the opinion of the investigator * Pregnant or breastfeeding * Use of prohibited concomitant therapy * History of severe allergy or hypersensitivity * Dependence on alcohol or illegal drugs * Use of any of the following medications during the trial: antipsychotic medications other than risperidone; psychostimulants; or antidepressants