The brief negative symptom scale: validation of the German translation and convergent validity with self-rated anhedonia and observer-rated apathy.

Background: Negative symptoms are considered core symptoms of schizophrenia. The Brief Negative Symptom Scale (BNSS) was developed to measure this symptomatic dimension according to a current consensus definition. The present study examined the psychometric properties of the German version of the BNSS. To expand former findings on convergent validity, we employed the Temporal Experience Pleasure Scale (TEPS), a hedonic self-report that distinguishes between consummatory and anticipatory pleasure. Additionally, we addressed convergent validity with observer-rated assessment of apathy with the Apathy Evaluation Scale (AES), which was completed by the patient's primary nurse.

Methods: Data were collected from 75 in- and outpatients from the Psychiatric Hospital, University Zurich diagnosed with either schizophrenia or schizoaffective disorder. We assessed convergent and discriminant validity, internal consistency and inter-rater reliability.

Results: We largely replicated the findings of the original version showing good psychometric properties of the BNSS. In addition, the primary nurses evaluation correlated moderately with interview-based clinician rating. BNSS anhedonia items showed good convergent validity with the TEPS.

Conclusions: Overall, the German BNSS shows good psychometric properties comparable to the original English version. Convergent validity extends beyond interview-based assessments of negative symptoms to self-rated anhedonia and observer-rated apathy.