General and specific cognitive deficits in schizophrenia.
BACKGROUND
It is controversial whether the cognitive deficit in schizophrenia is better characterized as generalized or as reflecting relatively independent deficits in different cognitive domains. The issue has implications for assessment practice, intervention design, and the exploration of schizophrenia genetics.


METHODS
We used a specialized structural equation modeling approach, single common factor analysis, to explore the relative importance of generalized versus independent cognitive deficits in schizophrenia. Eighteen subtest scores from the Wechsler Adult Intelligence Scale-III and the Wechsler Memory Scale-III were included in the analysis. We analyzed these data for 97 schizophrenia or schizoaffective disorder outpatients and 87 healthy control subjects.


RESULTS
Approximately two thirds of the overall effect of a schizophrenia diagnosis on cognitive performance was mediated through a single common factor. The Wechsler subtest scores showed almost uniformly strong relationships with this factor. The independent associations of group status with the subtest scores were smaller in magnitude and only selectively significant.


CONCLUSIONS
The relatively greater magnitude of illness effects mediated through the common factor in this analysis, compared with the specific, independent effects, suggests that a generalized cognitive deficit is a core feature of schizophrenia.
Dickinson
Dwight
D
Veterans Affairs Capitol Health Care Network, Mental Illness Research, Education, and Clinical Center, 10 North Greene Street, Suite 6A, Baltimore, MD 21201, USA.
Iannone
Virginia N
VN
Wilk
Christopher M
CM
Gold
James M
JM
D000328:Adult; D016022:Case-Control Studies; D003071:Cognition / Q000145:classification*; D003072:Cognition Disorders / Q000209:etiology*; D005163:Factor Analysis, Statistical; D005260:Female; D005793:Generalization, Psychological / Q000502:physiology; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology; D008875:Middle Aged; D015999:Multivariate Analysis; D016571:Neural Networks, Computer; D012559:Schizophrenia / Q000150:complications*; D014706:Verbal Learning / Q000502:physiology; D014888:Wechsler Scales / Q000706:statistics & numerical data