ReviewSocial and neuro-cognition as distinct cognitive factors in schizophrenia: A systematic review
Introduction
Cognitive dysfunction in schizophrenia, though described by Kraepelin nearly a century ago, has been studied systematically only in the last couple of decades (Harvey et al., 2001). Initial studies focused on basic neuro-cognitive dysfunction (George and Neufeld, 1985, Green et al., 2000); however subsequent studies have ushered in the concept of social cognition dysfunction in schizophrenia (Corrigan and Green, 1993, Savla et al., 2012). Both social cognition (SC) and neuro-cognition (NC) have potential roles as putative endophenotype markers in schizophrenia (Eack et al., 2010, Kalkstein et al., 2012), predictors of functional outcome (Vauth et al., 2004, Fett et al., 2011) and as targets for remediation (Hogarty et al., 2004). Evidence is still sparse as to whether SC and NC are better modeled as one or two separate constructs.
Conceptually, NC involves general information acquiring and processing functions like attention, vigilance, memory, processing speed and executive functions. It is relatively affect-neutral. NC functions are utilized across both non-social (e.g., driving a car) and social (e.g., responding to an angry colleague) situations. In contrast, SC represents the interface between emotional and cognitive processing, with an inter-subjective quality, requiring reflective (meta-cognitive) and social inferential abilities (Dimaggio et al., 2008). Dissociations between social and non-social cognition have been described in different clinical conditions. Subjects with pre-frontal lobe damage (Anderson et al., 1999), prosopagnosia (Kanwisher, 2000) and Asperger's syndrome (Klin, 2000) have relatively intact neuro-cognitive abilities but have impairments in SC. In contrast, individuals with Williams' syndrome tend to be social, despite having intellectual impairment (Jones et al., 2000).
Factor analytical studies are well suited to identify core domains of cognitive processes and thus establish the distinctiveness of SC and NC. They are useful in determining how individual cognitive processes cluster together, thus reducing a larger set of cognitive abilities to smaller subgroups (Kerlinger, 1979). Identifying groups of cognitive processes that co-vary with one another also help to define meaningful underlying latent variables (Nunnally, 1978), thus giving clues about the construct validity of these processes and their underlying pathophysiology. Exploratory factor analysis (FA) is used to obtain empirical constructs underlying a set of responses, by inspecting the patterns of co-variation represented by the correlations among individual responses (Costello and Osborne, 2005). This is utilized when there is a paucity of strong theoretical grounding about the constructs underlying cognitive processes. On the other hand, confirmatory FA is employed to determine the capacity of a predefined factor model to fit an observed set of data. This method can be used to confirm theoretical frameworks arising out of exploratory methods, in an independent sample (Hatcher, 1994). A number of such attempts have been made in schizophrenia patients.
Further, it is of interest to explore whether SC exists as a single or multi-factorial construct in schizophrenia. The National Institute of Mental Health workshop on social cognition (definitions, assessment and research opportunities) in schizophrenia, 2008, highlighted that there was in fact a paucity of data concerning the factor structure of SC in schizophrenia (Green et al., 2008). It also pointed out that such analyses were not common because very few studies included a broad range of social cognitive measures and had an adequate sample size. Since then, there have been attempts at exploring these questions. In this paper, we systematically review studies that report results of factor analysis (FA) of SC and NC in schizophrenia, to explore (a) the distinctiveness of SC and NC domains, and (b) factor structure of SC.
Section snippets
Methods
We searched published scientific literature in MEDLINE and PsychINFO databases with the following search strategy: [(“factor analysis” OR “principal components analysis”) AND (“social cognition” OR “theory of mind” OR “emotion recognition” OR “emotion processing” OR “emotion regulation” OR “social perception” OR “social knowledge” OR “attributional style” OR “attributional bias”) AND (“schizophrenia” OR “psychosis”)]. Studies were included if 1. The study assessed social cognition domains as
Results
The results are described under three sections: (a) Evidence for distinct SC and NC factors, (b) Evidence for Factor structure of SC and (c) Quality check of the reporting practices of the FA studies. The first two sections contain a summary followed by analysis of influence of potential effect modifiers. Table 1 gives an overview of the 20 selected studies, their sample characteristics, cognitive tests used, methods of FA, factors extracted and their clinical relevance. Supplementary Tables 2
Discussion
In this paper, we systematically collated evidence regarding two important questions pertaining to factor structure of social cognition in schizophrenia: (a) Are SC and NC distinct cognitive domains? (b) Is SC a unitary cognitive domain?
Role of the funding source
The funding agency (ICMR) did not have any role in conceptualizing and writing the manuscript.
Contributors
UMM conceptualized the review, performed the literature search, and drafted the manuscript. JT and BNG supervised the literature review and contributed to drafting of the manuscript. DKS gave inputs on statistical aspects of methodology of factor analyses and quality check in reporting studies. SME and MSK helped in interpreting the results and edited the manuscript. All authors contributed to and have approved the final manuscript.
Conflict of interest
All authors declare that they have no conflicts of interest.
Acknowledgments
We thank the Indian Council of Medical Research (MD financial assistance award 2007–2009 No. 3/2/2008/PG-Thesis-MPD-29 to UM Mehta) for the financial support.
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