title: The impact of premorbid and current intellect in schizophrenia: cognitive, symptom, and functional outcomes.
abstract: BACKGROUND
  Cognitive heterogeneity among people with schizophrenia has been defined on the basis of premorbid and current intelligence quotient (IQ) estimates. In a relatively large, community cohort, we aimed to independently replicate and extend cognitive subtyping work by determining the extent of symptom severity and functional deficits in each group.
  
  
  METHODS
  A total of 635 healthy controls and 534 patients with a diagnosis of schizophrenia or schizoaffective disorder were recruited through the Australian Schizophrenia Research Bank. Patients were classified into cognitive subgroups on the basis of the Wechsler Test of Adult Reading (a premorbid IQ estimate) and current overall cognitive abilities into preserved, deteriorated, and compromised groups using both clinical and empirical (k-means clustering) methods. Additional cognitive, functional, and symptom outcomes were compared among the resulting groups.
  
  
  RESULTS
  A total of 157 patients (29%) classified as 'preserved' performed within one s.d. of control means in all cognitive domains. Patients classified as 'deteriorated' (n=239, 44%) performed more than one s.d. below control means in all cognitive domains except estimated premorbid IQ and current visuospatial abilities. A separate 138 patients (26%), classified as 'compromised,' performed more than one s.d. below control means in all cognitive domains and displayed greater impairment than other groups on symptom and functional measures.
  
  
  CONCLUSIONS
  In the present study, we independently replicated our previous cognitive classifications of people with schizophrenia. In addition, we extended previous work by demonstrating worse functional outcomes and symptom severity in the compromised group.
authors.affiliation: School of Psychiatry, University of New South Wales, Sydney, NSW, Australia; Neuroscience Research Australia, Randwick, Sydney, NSW, Australia.
authors.forename: Ruth
authors.initials: R
authors.lastname: Wells
authors.affiliation: Department of Psychiatry, University of Melbourne, Parkville, VIC, Australia; Northern Psychiatry Research Centre, North Western Mental Health, Melbourne Health, Victoria, Australia; Schizophrenia Research Institute, Sydney, NSW, Australia; Molecular Psychopharmacology Laboratory, The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia.
authors.forename: Vaidy
authors.initials: V
authors.lastname: Swaminathan
authors.affiliation: Department of Psychiatry, University of Melbourne, Parkville, VIC, Australia; Northern Psychiatry Research Centre, North Western Mental Health, Melbourne Health, Victoria, Australia; Molecular Psychopharmacology Laboratory, The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia.
authors.forename: Suresh
authors.initials: S
authors.lastname: Sundram
authors.affiliation: School of Psychiatry, University of New South Wales, Sydney, NSW, Australia; Neuroscience Research Australia, Randwick, Sydney, NSW, Australia.
authors.forename: Danielle
authors.initials: D
authors.lastname: Weinberg
authors.affiliation: School of Psychiatry, University of New South Wales, Sydney, NSW, Australia; Neuroscience Research Australia, Randwick, Sydney, NSW, Australia.
authors.forename: Jason
authors.initials: J
authors.lastname: Bruggemann
authors.affiliation: Neuroscience Research Australia, Randwick , Sydney, NSW, Australia.
authors.forename: Isabella
authors.initials: I
authors.lastname: Jacomb
authors.affiliation: Department of Psychiatry, University of Melbourne , Parkville, VIC, Australia.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Cropley
authors.affiliation: School of Psychiatry, University of New South Wales, Sydney, NSW, Australia; Neuroscience Research Australia, Randwick, Sydney, NSW, Australia; Schizophrenia Research Institute, Sydney, NSW, Australia.
authors.forename: Rhoshel
authors.initials: R
authors.lastname: Lenroot
authors.affiliation: Department of Psychiatry, University of Melbourne, Parkville, VIC, Australia; Molecular Psychopharmacology Laboratory, The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia.
authors.forename: Avril M
authors.initials: AM
authors.lastname: Pereira
authors.affiliation: Department of Psychiatry, University of Melbourne , Parkville, VIC, Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Zalesky
authors.affiliation: Department of Psychiatry, University of Melbourne , Parkville, VIC, Australia.
authors.forename: Chad
authors.initials: C
authors.lastname: Bousman
authors.affiliation: Department of Psychiatry, University of Melbourne, Parkville, VIC, Australia; Schizophrenia Research Institute, Sydney, NSW, Australia.
authors.forename: Christos
authors.identifier: 0000-0002-9565-0238
authors.initials: C
authors.lastname: Pantelis
authors.affiliation: School of Psychiatry, University of New South Wales, Sydney, NSW, Australia; Neuroscience Research Australia, Randwick, Sydney, NSW, Australia; Schizophrenia Research Institute, Sydney, NSW, Australia.
authors.forename: Cynthia Shannon
authors.initials: CS
authors.lastname: Weickert
authors.affiliation: School of Psychiatry, University of New South Wales, Sydney, NSW, Australia; Neuroscience Research Australia, Randwick, Sydney, NSW, Australia; Schizophrenia Research Institute, Sydney, NSW, Australia.
authors.forename: Thomas W
authors.identifier: 0000-0002-6408-718X
authors.initials: TW
authors.lastname: Weickert