The BPRS is a clinician-rated tool designed to assess change in severity of psychopathology. It has been in widespread use for more than 30 years and remains popular for research studies that assess patient change in response to treatment interventions. It is an 18-item scale measuring positive symptoms, general psychopathology and affective symptoms. Each symptom construct is rated on a 7-point scale of severity ranging from 'not present' to 'extremely severe.' It takes approximately 20-30 minutes to administer the BPRS.