Defining and measuring negative symptoms of schizophrenia in clinical trials.

Recent attention has focused on negative symptoms as a target for new therapeutic approaches including pharmacological agents, medical devices, and psychosocial treatments. Each of these approaches requires an instrument for measuring the severity of negative symptoms as well as changes in severity over time. The instrument selected should provide coverage for the domains of negative symptoms; it should be sensitive to change; it should be reliable and relatively brief; and it should be useful for large international trials. These criteria were used to evaluate a number of older instruments including the Schedule for the Assessment of Negative Symptoms (SANS), the Positive and Negative Symptoms Scale (PANSS), and the Negative Symptom Assessment Scale (NSA). Two newer scales, the Brief Negative Symptom Scale (BNSS) and the Clinical Assessment Interview for Negative Symptoms (CAINS) were developed following a National Institute of Mental Health consensus meeting and addressed some of the shortcomings of earlier instruments.