title: Defining a cognitive function decrement in schizophrenia.
abstract: BACKGROUND
  Although cognitive impairment is described as a core component of the characterization of schizophrenia, a sizable percentage of patients are classified as unimpaired by traditional definitions of impairment. The purpose of this study was to determine the percentage of patients with schizophrenia meeting criteria for a "cognitive function decrement" defined as a current level of cognitive function that falls below the level predicted by premorbid estimates.
  
  
  METHODS
  Linear regression analyses were performed on a healthy control population to determine a predicted composite cognitive score based on maternal education, paternal education, and reading score as indicators of premorbid intellectual function. The percentages of patients with current cognitive function above and below predicted values were calculated.
  
  
  RESULTS
  When the Wide Range Achievement Test-3 (WRAT-3) score and maternal education are both used to predict current cognitive performance, as expected, about half (42%) of control subjects fall below expectations. However, 98.1 % of patients fall below expectations.
  
  
  CONCLUSIONS
  When cognitive function decrement is defined as a failure to reach the expected level of cognitive functioning, almost all patients with schizophrenia meet this definition.
authors.affiliation: Duke University, School of Medicine, Durham, North Carolina, USA. richard.keefe@duke.edu
authors.forename: Richard S E
authors.initials: RS
authors.lastname: Keefe
authors.forename: Charles E
authors.initials: CE
authors.lastname: Eesley
authors.forename: Margaret P
authors.initials: MP
authors.lastname: Poe
mesh_terms: D003072:Cognition Disorders / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology; D016001:Confidence Intervals; D006801:Humans; D007360:Intelligence / Q000502:physiology; D007361:Intelligence Tests; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D012044:Regression Analysis; D012559:Schizophrenia / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology; D012565:Schizophrenic Psychology