Variability in BPRS definitions of positive and negative symptoms

Reviewing Brief Psychiatric Rating Scale (BPRS) research indicates that combining items to form larger 'symptom factors' (e.g., depression, psychosis) has become the standard methodology. Unfortunately, a single symptom factor may be defined by different combinations of different BPRS items in different studies. To examine the potential impact of these differences, a number of different BPRS definitions of positive and negative symptoms in schizophrenia were culled from previous research. To compare these definitions, one hundred schizophrenics were interviewed with regard to current and recent symptomatology and rated on the BPRS, the Schedule for the Assessment of Negative Symptoms (SANS), and the Schedule for the Assessment of Positive Symptoms (SAPS). The four BPRS negative symptom definitions all correlated highly with one another and with the SANS. There were no differences in the amount that these different definitions of negative symptoms correlated with the SANS. Also, the nine definitions of positive symptoms all correlated highly with one another and with the SAPS. However, there were significant differences in how they correlated with the SAPS. Because of these differences, possible standard definitions for negative and positive symptoms of schizophrenia are proposed for future use of the BPRS in research.