title: Cognitive factor structure and invariance in people with schizophrenia, their unaffected siblings, and controls.
abstract: BACKGROUND
  Separable, but positively correlated, factors emerge from analyses of cognitive test data in schizophrenia and control samples (eg, verbal memory and processing speed) and these factors guide data reduction. Additionally, data support a hierarchical model of cognitive performance, in which these correlations reflect the influence of a higher-order factor, referred to as "g." We tested these findings in large, carefully screened samples of people with schizophrenia (n = 496), their unaffected siblings (n = 504), and controls (n = 823). Furthermore, we tested the hypothesis that cognitive performance in schizophrenia is more generalized across domains than among siblings and controls.
  
  
  METHODS
  A combination of exploratory and confirmatory factor analyses (EFA and CFA) and multiple groups CFA (MCFA) was used.
  
  
  RESULTS
  EFA yielded factors for verbal memory, visual memory, processing speed, working memory span, nback performance, and card sorting. The solution was consistent across groups, in terms of the factor assignments of individual cognitive variables and the magnitude of loadings. Method variance may have contributed to the card sorting, visual memory, and nback factors. CFA indicated that the hierarchical model, incorporating a "g" factor, was a good fit for data from all groups. MCFA suggested that this hierarchical structure was fully invariant for controls and siblings. While the variable/factor loadings for the schizophrenia group also were invariant with comparison groups, factor/"g" loadings were higher in schizophrenia, as were correlations among factor-based composite scores.
  
  
  CONCLUSIONS
  Cognitive variables sort into domains consistently in schizophrenia, unaffected siblings, and controls. However, performance in schizophrenia is more generalized and less domain specific.
authors.affiliation: National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA. Dwight.Dickinson@nih.gov
authors.forename: Dwight
authors.initials: D
authors.lastname: Dickinson
authors.forename: Terry E
authors.initials: TE
authors.lastname: Goldberg
authors.forename: James M
authors.initials: JM
authors.lastname: Gold
authors.forename: Brita
authors.initials: B
authors.lastname: Elvevåg
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Weinberger
mesh_terms: D000293:Adolescent; D000328:Adult; D003071:Cognition; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D012559:Schizophrenia / Q000235:genetics; D012565:Schizophrenic Psychology; D012720:Severity of Illness Index; D035781:Siblings / Q000523:psychology*; D055815:Young Adult