The nature and functional significance of intra-individual neurocognitive ability across serious mental illness diagnoses
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Intra-individual performance variability (IIV) is defined as lawful, transient, within-person changes in cognitive performance. IIV has been found to predict functional and other crucial real-world outcomes among clinical populations with characteristic frontal lobe abnormalities. However, little is known about its significance among individuals with serious mental illness (SMI). Moreover, IIV’s relationships to clinical, cognitive, diagnostic, and demographic variables in this population are yet uncertain. The aims of this study were (1) to characterize intra-individual neurocognitive performance variability among participants with serious mental illness (2) to examine possible differences in levels of IIV across diagnostic and educational groups, (3) and to explore its functional significance among participants with SMI, including its incremental validity to predict employment and living status outcomes, and performance on a test of grocery shopping skills. We completed a secondary analysis using data from 217 participants representing community-dwelling adults with either a psychotic disorder or an affective disorder diagnosis. We found that age, clinical symptoms, and overall cognitive ability were not significantly related to IIV among participants. Psychotic and affective disorder groups evidenced similar levels of IIV, irrespective of positive and negative symptoms. IIV did not vary across groups with different levels of education. Further, IIV was not related to functional outcomes nor incrementally predictive of them, above and beyond overall cognitive ability. Future research may address limitations of the present study and explore interrelationships between IIV, cognitive effort, and disengaged lifestyle among individuals with SMI in the absence of relationships between IIV and our variables of interest.
Table of Contents
Introduction -- Review of the literature -- Methodology -- results -- Discussion
M.A. (Master of Arts)