Assessment of negative symptoms and depression in schizophrenia: revision of the SANS and how it relates to the PANSS and CDSS.

OBJECTIVE: The Scale for the Assessment of Negative Symptoms (SANS) is the most widely used instrument for measuring negative symptoms in schizophrenia. The validity of its factor structure has not been established. Congruence of the SANS and its subscales to the negative subscale of the Positive and Negative Symptom Scale (PANSS-N) and the Calgary Depression Scale for Schizophrenia (CDSS) were never explored. The current study revised SANS's structure and examined its correlations with the PANSS and the CDSS.
METHOD: Two-hundred and forty patients with schizophrenia with predominantly negative symptoms were analyzed. A principal component analysis was conducted for SANS. Spearman's correlations were conducted for SANS and PANSS-N, and for SANS and CDSS.
RESULTS: Principal Component Analyses (PCA) of SANS revealed four factors, corresponding to the original SANS subscales with two exceptions: Item #13 (grooming and hygiene) loaded on the alogia factor rather than on its original affective flattening factor, and Item #4 (poor eye contact) did not load onto any factor. The total PANSS-N score showed a moderate correlation with the SANS and all of its subscales. The total CDSS score showed a low negative correlation with the total SANS score and with its avolition subscale.
CONCLUSIONS: Our results supported the validity of SANS's structure except for "poor eye contact" and "grooming end hygiene". The moderate correlation between SANS and PANSS-N suggests that although they are not identical, they measure similar constructs. The low negative correlation between SANS and CDSS suggests that they measure different constructs.