title: Cognitive heterogeneity in first-episode schizophrenia.
abstract: BACKGROUND
  Studies of chronic schizophrenia suggest that there are subgroups with different profiles of cognitive impairment.
  
  
  OBJECTIVE
  To determine whether such heterogeneity is present at illness onset and any relationship to clinical variables.
  
  
  METHODS
  Ninety-three community patients with first-episode schizophrenia and 50 healthy volunteers were assessed for premorbid (Revised National Adult Reading Test) and current IQ, memory and executive function.
  
  
  RESULTS
  Half of those with schizophrenia had preserved IQ in the normal range but there was evidence of a specific impairment in spatial working memory even in those with high/average IQ; 37 out of 93 (40%) had generalised cognitive decline. Those with low premorbid IQ were significantly younger at illness onset. For the entire group, age at onset correlated positively with premorbid but not current IQ.
  
  
  CONCLUSIONS
  At illness onset, cognitive heterogeneity is present in people with schizophrenia, with a high proportion having undergone general cognitive decline. However, working memory impairment may be a common feature. Lower premorbid IQ is a risk factor for an earlier onset.
authors.affiliation: Institute of Neurology, University College London, Box 19, The National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK. e.joyce@ion.ucl.ac.uk
authors.forename: Eileen M
authors.initials: EM
authors.lastname: Joyce
authors.forename: Sam B
authors.initials: SB
authors.lastname: Hutton
authors.forename: Stanley H
authors.initials: SH
authors.lastname: Mutsatsa
authors.forename: Thomas R E
authors.initials: TR
authors.lastname: Barnes
mesh_terms: D000328:Adult; D000367:Age Factors; D017668:Age of Onset; D002908:Chronic Disease; D003072:Cognition Disorders / Q000150:complications / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007360:Intelligence; D007361:Intelligence Tests; D008297:Male; D008569:Memory Disorders / Q000150:complications / Q000175:diagnosis; D009483:Neuropsychological Tests; D012565:Schizophrenic Psychology