The Negative Symptom Rating Scale: Initial Evaluation of Reliability and Validity
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Negative symptoms in schizophrenia are a major determinant of the social and occupational impairments that characterize the disorder, as well as a significant source of distress for caregivers, and predictors of poor long-term outcome. Despite the compelling evidence for the clinical relevance of negative symptoms, this domain of the illness remains inadequately addressed by current pharmacotherapy and psychotherapy. As identified at the NIMH-MATRICS Consensus Development Conference on Negative Symptoms, a significant barrier to progress in the treatment of this symptom domain is the current lack of an adequate measure for assessment of negative symptoms (Kirkpatrick et al., 2006). It was in response to this need that the NIMH-MATRICS Negative Symptom Workgroup developed a new measure, the Negative Symptom Rating Scale (NSRS). The current study provided the first evaluation of the psychometric properties of the newly developed NSRS, including the inter-rater agreement and internal consistency of the NSRS scales, and assessed convergent and discriminant validity. The results of this initial psychometric evaluation of the NSRS are generally quite encouraging, and provide information that has helped inform data-driven modifications to the measure for upcoming validation studies. With regards to reliability, the NSRS demonstrated adequate internal consistency for the scale as a whole, and for three of the five subscales. The results indicated that the Asociality and Avolition subscales warrant further revisions or modifications to improve internal consistency. Additionally, three of the five subscales were found to have good to excellent interrater reliability, with the Avolition and Alogia subscales falling in the fair range. Results generally demonstrated adequate convergent validity between the NSRS and other measures of negative symptoms, namely the SANS and the BPRS Anergia subscale. Additionally, results indicated general convergence between clinician-rated anhedonia using the NSRS and self-reported anhedonia as measured by the TEPS. Finally, the NSRS showed discrimination from ratings of psychotic and depressive symptoms. The results of the present study point to areas in which revisions are necessary, and has provided valuable information that is necessary for making revisions and modifications to the measure prior to larger scale evaluation.