Predictors of Longitudinal Changes in Schizophrenia: The Role of Processing Speed

Background: The main objective was to identify variables that predict functional disability in chronic schizophrenia over time. Method: We examined 95 hospitalized patients with schizophrenia (DSM-IV criteria) in a long-stage unit and 53 healthy controls (matched for age, gender, and years of education). Neuropsychological battery included tests for verbal memory, working memory, executive functioning, and processing speed. Functional disability was assessed at 6-month follow-up with the Disability Assessment Schedule after the neuropsychological and clinical assessment. The study was conducted from September 2005 to July 2008. Results: Patient performance was significantly lower than that of the healthy comparison subjects on all neurocognitive variables (p < .001). Most, but not all, neurocognitive measures were significantly correlated with the patients' functional disability shown 6 months after admission to the study, including self-care management, vocational outcome, family contact, and social functioning. Results suggest that processing speed has a significant influence in these relationships. Conclusions: Processing speed plays an outstanding role in the relationship between neurocognitive symptoms and self-care, vocational outcome, and social functioning. Our data support the possibility of processing speed as the best longitudinal predictor of the level of autonomy in patients with chronic schizophrenia. (J Clin Psychiatry 2009; 70(6):888-896) (C) Copyright 2008 Physicians Postgraduate Press, Inc.