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Diagnosis and family membership-dependent cognitive domain impairment in schizophrenia patients and their unaffected siblings

University of British Columbia

The goals of the present research were two-fold: (1) to examine whether diagnosis-dependent group differences in cognitive performance among schizophrenia patients, their unaffected siblings and healthy controls are fundamentally the result of a general cognitive impairment and/or of domain-specific deficits in schizophrenia; and (2) to examine the cognitive domains that characterize family membership-dependent and family membership-independent group differences in cognitive performance between schizophrenia patients and their siblings. In Study 1, results from a traditional statistical analysis method suggested impairment in all five cognitive domains tested, whereas constrained principal component analysis (CPCA) revealed a single cognitive domain accounting for group differences that extended across all five traditional domains. This component reflected impairment in a generalized cognitive domain in schizophrenia patients and, to a lesser degree, siblings, and was dominated by WAIS-R Digit Symbol and WMS-R Logical Memory subscales, a finding in line with literature reporting most severe impairment in information processing speed and verbal memory in schizophrenia. In Study 2, CPCA with hierarchical regression was used to examine the cognitive domains that accounted for the interaction between group and family membership, revealing three cognitive domains (Working Memory/Attention, Visual Memory, and Verbal Memory) where differences between patients and their siblings depended on family membership. A subsequent cluster analysis revealed several family clusters differing on patients’ and siblings’ performance across these three cognitive domains. The results of the current research suggest that (1) diagnosis-based group differences in cognitive performance are due to impairment in a generalized cognitive domain (and not primarily within more specific cognitive domains) that is common to all families, (2) this general impairment is best captured by measures of information processing speed and verbal memory, and that (3) family membership-dependent group differences are present in more specific cognitive domains that are distinguishable from the general domain describing overall group differences. This research helps synthesize the two sides of the debate surrounding the nature of cognitive impairment in schizophrenia, by suggesting that there is impairment in both a generalized cognitive domain and in more specific domains, but that the latter may depend on moderating factors, such as family membership.

Text

2013-08-29

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/44945

Neuroscience

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/