Objective: Schizophrenia and bipolar disorder are associated with multidimensional disability. This study examined differential predictors of functional deficits in the two disorders.
Method: Community-dwelling individuals with schizophrenia (N=161) or bipolar disorder (N=130) were assessed with neuropsychological tests, symptom measures, and performance-based social and adaptive (i.e., everyday living skills) functional competence measures as well as three domains of real-world functioning: community and household activities; work skills; and interpersonal relationships. The authors used confirmatory path analysis to find the best-fitting models to examine the direct and indirect (as mediated by competence) prediction of the three domains of real-world functioning.
Results: In all models for both groups, neurocognition's relationship with outcomes was largely mediated by competence. Symptoms were negatively associated with outcomes but unassociated with competence, with the exception of depression, which was a direct and mediated (through social competence) predictor in bipolar disorder. In both groups, neurocognition was related to activities directly and through a mediated relationship with adaptive competence. Work skills were directly and indirectly (through mediation with social competence) predicted by neurocognition in schizophrenia and entirely mediated by adaptive and social competence in bipolar disorder. Neurocognition was associated with interpersonal relationships directly in the schizophrenia group and mediated by social competence in both groups.
Conclusions: Although there was greater disability in schizophrenia, neurocognition predicted worse functioning in all outcome domains in both disorders. These results support the shared role of neurocognition in bipolar disorder and schizophrenia in producing disability, with predictive differences between disorders in domain-specific effects of symptoms and social and adaptive competence.