Patients in the first-phase screening Patients diagnosed with schizophrenia or schizoaffective disorder according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition; aged 20-65 years; and who had taken clozapine for at least 3 months were invited to the first-phase screening. Clinical interviews were conducted, and medical records were evaluated for collecting patient demographics and clinical information, namely diagnosis, age of onset, and dosage of clozapine use.