Neuropsychological deficit and symptomatology: Evidence for the heterogeneity of positive symptoms

Abstract

The positive-negative symptom dichotomy has strongly influenced recent conceptualizations of the nature of schizophrenia. Several studies have now shown that negative symptoms are significantly associated with one another but that intercorrelations among positive symptoms are less strong. A recent factor analytic study by our group on the SANS/SAPS found three factors rather than the two suggested by the positive-negative distinction (Arndt, Alliger & Andreasen, Br J Psychiatry, in press). Negative global scores made up one clear factor but positive globals split, with hallucinations and delusions making up one factor and positive formal thought disorder (PFTD) and bizarre behavior forming another. The present study explores the possibility that positive symptoms may be differentially related to cognitive performance. Data will be reported from three independent samples of schizophrenics (DSM-III criteria) studied at the University of Iowa Psychiatric Hospital. All patients received a comprehensive neuropsychological battery. Severity of negative symptoms was found to be related to a wide range of cognitive deficits including lower IQ scores and poorer performance on measures of attention and memory. Severity of hallucinations and delusions, in contrast, was not significantly related to deficiencies on any measure in the battery. Patients with high ratings on PFTD and bizarre behavior showed a pattern of cognitive disorganization that was less consistent across the three studies than the generalized deficit associated with negative symptoms. The results support previous findings that negative symptoms are associated with cognitive deficit that may reflect underlying brain pathology. Florid positive symptoms show no evidence of association with cognitive impairment. We will discuss the possibility that the cognitive disorganization associated with PFTD and bizarre behavior reflects a neuropathological process independent of that associated with negative symptoms.