Symptom structure in schizophrenia: two-, three- or four-factor models?

Beside the syndromic dichotomy (negative-positive), other symptomatic dimensions have been described in schizophrenia. A question of interest is, therefore, to know which symptom structures can be individualized to characterize schizophrenia. Using confirmatory factor analysis in 135 patients, a two-factor model (negative-positive), a three-factor model (negative-positive-disorganization) and a four-factor model (negative-positive-disorganization-relational) were primarily identified with SANS (Scale for the Assessment of Negative Symptoms) and SAPS (Scale for the Assessment of Positive Symptoms). In contrast, no models could be identified with PANSS (Positive and Negative Syndrome Scale). The results confirm the relevance of other syndrome dimensions, beside the negative and positive ones and suggest that SANS-SAPS was more useful than PANSS in identifying an adequate dimensional factor structure of schizophrenic symptoms.