title: Dimensions of executive functioning in schizophrenia and their relationship with processing speed.
abstract: BACKGROUND
  The nature of executive dysfunction in schizophrenia is nebulous, due to inconsistencies in conceptualizing and operationalizing the construct, and the broader question of whether schizophrenia is best characterized in terms of specific vs generalized cognitive deficits. The current study aimed to determine whether executive functions represent unitary vs diverse constructs in schizophrenia.
  
  
  METHODS
  Participants included 145 community-dwelling individuals with schizophrenia. Executive functions were measured with the Delis-Kaplan Executive Functioning System (D-KEFS). We conducted an exploratory factor analysis (EFA) with principal axis factoring, as well as parallel analyses to examine the latent constructs underlying the D-KEFS tasks, a second EFA on weighted residuals of the D-KEFS tasks (after accounting for processing speed measured with the Digit Symbol task), and bivariate correlations to examine relationships between the D-KEFS components and relevant demographic and clinical variables, crystallized verbal knowledge, and functional capacity.
  
  
  RESULTS
  EFA of the D-KEFS tasks yielded 2 factors (cognitive flexibility/timed tests and abstraction). EFA of the processing speed-weighted D-KEFS residuals also yielded 2 factors (cognitive flexibility and abstraction). Cognitive flexibility was negatively correlated with psychopathology. Better abstraction was associated with higher education, shorter illness duration, and better functional capacity. Both factors were positively correlated with crystallized verbal knowledge.
  
  
  CONCLUSIONS
  Executive functions in schizophrenia could be parsed into 2 partially related but separable subconstructs. Future efforts to elucidate functional outcomes as well as neurobiological underpinnings of schizophrenia may be facilitated by attending to the distinction between cognitive flexibility and abstraction.
authors.affiliation: Department of Psychiatry, University of California, San Diego, 9500 Gilman Drive, MC 0603V, La Jolla, CA 92093-0603, USA. gsavla@ucsd.edu
authors.forename: Gauri N
authors.initials: GN
authors.lastname: Savla
authors.forename: Elizabeth W
authors.initials: EW
authors.lastname: Twamley
authors.forename: Dean C
authors.initials: DC
authors.lastname: Delis
authors.forename: Scott C
authors.initials: SC
authors.lastname: Roesch
authors.forename: Dilip V
authors.initials: DV
authors.lastname: Jeste
authors.forename: Barton W
authors.initials: BW
authors.lastname: Palmer
mesh_terms: D000328:Adult; D003072:Cognition Disorders / Q000209:etiology / Q000503:physiopathology*; D056344:Executive Function; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D011594:Psychometrics / Q000295:instrumentation; D011618:Psychotic Disorders / Q000150:complications / Q000503:physiopathology; D012559:Schizophrenia / Q000150:complications / Q000503:physiopathology*