A two-factor structure for the Schedule for the Deficit Syndrome in schizophrenia.

The deficit subtype is hypothesized to constitute a homogeneous subgroup of schizophrenia patients. The Schedule for the Deficit Syndrome (SDS) was developed to categorize schizophrenia patients into deficit and non-deficit subtypes. Only one report, however, has suggested the use of a two-factor SDS. The present study used a two-factor SDS and examined the relationships between the factors and the demographic and clinical variables in deficit-type schizophrenia patients. Principal component analysis was performed on data obtained from 70 schizophrenia patients with the deficit syndrome. The two-factor SDS was replicated. Factor 1, avolition, was significantly correlated only with the relational disorder domain, which consisted of two negative items from the Positive and Negative Syndrome Scale. Factor 2, poor emotional expression, was significantly correlated with both the negative symptom domain, which consisted of three negative items, and the relational disorder domain. Since the SDS has two factors, there appear to be different underlying processes for these two factors.