title: Stability of cognitive impairment in chronic schizophrenia over brief and intermediate re-test intervals.
abstract: OBJECTIVE
  This study examined between- and within-subject stability of cognitive performance in individuals with chronic schizophrenia.
  
  
  METHODS
  Thirty individuals with schizophrenia and 20 healthy controls matched by age, sex, education, and estimated IQ underwent repeated cognitive assessments at baseline and 30 days using computerized tests of psychomotor function, visual attention/information processing, non-verbal learning, and executive function.
  
  
  RESULTS
  Compared to healthy controls, individuals with schizophrenia scored lower on all cognitive measures and demonstrated greater variability in cognitive performance. Within-subject variability in cognitive performance in both the schizophrenia and healthy control groups remained stable at brief (i.e., hours) and intermediate (i.e., one month) assessments.
  
  
  CONCLUSIONS
  These results demonstrate the stability of between- and within-subject variability in cognitive performance in schizophrenia, and suggest that variability in cognitive performance may reflect an inherent characteristic of the disorder, rather than differences in test-retest reliability/error of cognitive measures.
authors.affiliation: Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut, USA.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Pietrzak
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Snyder
authors.forename: Colleen E
authors.initials: CE
authors.lastname: Jackson
authors.forename: James
authors.initials: J
authors.lastname: Olver
authors.forename: Trevor
authors.initials: T
authors.lastname: Norman
authors.forename: Danijela
authors.initials: D
authors.lastname: Piskulic
authors.forename: Paul
authors.initials: P
authors.lastname: Maruff
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002908:Chronic Disease; D003072:Cognition Disorders / Q000209:etiology / Q000503:physiopathology*; D003936:Diagnosis, Computer-Assisted; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D011597:Psychomotor Performance; D015203:Reproducibility of Results; D012559:Schizophrenia / Q000503:physiopathology*; D013997:Time Factors