Assessment of Negative Symptoms

Abstract

Negative symptoms are a fundamental dimension of schizophrenia despite of their limited role in the international diagnostic classifications. Eighteen instruments are identified of which 11 assess specifically the negative symptoms. The assessment of subjective experience is neglected in most of these negative symptom rating scales. Consequently, we present a new scale, the Self-report of Negative Symptoms (SNS), assessing the 5 consensual negative dimensions (emotional blunting, alogia, social withdrawal, anhedonia and avolition). This scale is an auto-evaluation constituted of 20 questions with a score ranging from 0 to 40.

Forty nine patients with schizophrenia and schizoaffective disorders (DSMIV) were evaluated in order to demonstrate three components of the scale’s validity: face and content validities and reliability.

No item was judged inappropriate or poorly formulated (face validity). According to experts, the universe of items clearly covers all the negative symptoms (content validity). The Cronbach’s coefficient (α=0.784) showed a good internal consistency (reliability). Factor analysis extracted 1 factor which accounted for 56.75% of the variance. Moreover, the SNS scores were significantly correlated with the SANS scores (r=0.526, p<0.001) and the negative CGI scores (r=0.599, p<0.001) supporting a good convergent validity. In contrast, there was no correlation between the SNS scores and the self-report insight scores demonstrating that patients with negative symptoms can evaluate themselves their negative symptoms independently of their level of insight of illness.

In conclusion, self-report of negative symptoms should be more used in clinical practice since it might allow the patients with schizophrenia to develop appropriate coping strategies.