Negative symptoms in bipolar disorder and schizophrenia: A psychometric evaluation of the brief negative symptom scale across diagnostic categories.

Past studies have demonstrated that the Brief Negative Symptom Scale (BNSS) has excellent psychometric properties in patients with schizophrenia. In the current study, we extended this literature by examining psychometric properties of the BNSS in outpatients diagnosed with bipolar disorder (n=46), outpatients with schizophrenia (n=50), and healthy controls (n=27). Participants completed neuropsychological testing and a clinical interview designed to assess negative, positive, disorganized, mood, and general psychiatric symptoms. Results indicated differences among the 3 groups in the severity of all BNSS items, with SZ and BD scoring higher than CN; however, SZ and BD only differed on blunted affect and alogia items, not anhedonia, avolition, or asociality. BD patients with a history of psychosis did not differ from those without a history of psychosis on negative symptom severity. The BNSS had excellent internal consistency in SZ, BD, and CN groups. Good convergent and discriminant validity was apparent in SZ and BD groups, as indicated by relationships between the BNSS and other clinical rating scales. These findings support the validity of the BNSS in broadly defined serious mental illness populations.