Heterogeneous patterns of cognitive and clinical impairment in diagnostic subtypes of schizoaffective disorder and schizophrenia

Authors

• EJ Giangrande
• DR Weinberger
• KF Berman
• D Dickinson

Abstract

Background: It is unclear whether schizoaffective disorder (SzAff) is a distinct disorder, a form of schizophrenia (Sz) or bipolar disorder, or part of a continuum between schizophrenia and affective diagnoses. Some research suggests that cognitive performance in SzAff is intermediate between Sz and bipolar disorder, and that the bipolar and depressive subtypes of SzAff can be differentiated on the basis of cognition. Hill et al. (2013) compared SzAff subtypes to an undivided Sz sample on cognition. The present study extends earlier work by comparing diagnostic subtypes of both SzAff and Sz on a range of cognitive and clinical phenotypes. Methods: Data for 38 SzAff bipolar (SzAffBp), 41 SzAff depressive (SzAffDep), 247 undifferentiated Sz, 160 paranoid Sz, and 54 disorganized Sz were available from the NIMH Study of Genetic Risk for Schizophrenia. Error bar graphs and GLM analyses compared SzAff and Sz diagnostic subtypes on selected variables. Results: SzAffBp performed worse than SzAffDep on most cognitive measures. The paranoid Sz group outperformed the undifferentiated and disorganized groups cognitively, while disorganized individuals showed the greatest impairment. SzAffBp was similar to disorganized Sz on several cognitive variables, but numerically outperformed other groups in reading ability, while SzAffDep closely resembled paranoid Sz. SzAffDep showed reduced symptoms, overall, but high levels of distress. Conclusions: Group comparisons revealed a complex pattern of similarities and differences in cognitive and clinical variables across SzAff and Sz subtypes, rather than a smooth continuum. Examining diagnostic subtypes rather than broad diagnoses provides insight into the heterogeneity of psychotic disorders.

Scientific Focus Area: Social and Behavioral Sciences

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