The impact of premorbid and current intellect in schizophrenia: cognitive, symptom, and functional outcomes

Ruth Wells; Vaidy Swaminathan; Suresh Sundram; Danielle Weinberg; Jason Bruggemann; Isabella Jacomb; Vanessa Cropley; Rhoshel Lenroot; Avril M Pereira; Andrew Zalesky; Chad Bousman; Christos Pantelis; Cynthia Shannon Weickert; Thomas W Weickert

doi:10.1038/npjschz.2015.43

The impact of premorbid and current intellect in schizophrenia: cognitive, symptom, and functional outcomes

NPJ Schizophr. 2015 Nov 4:1:15043. doi: 10.1038/npjschz.2015.43. eCollection 2015.

Authors

Affiliations

¹ School of Psychiatry, University of New South Wales, Sydney, NSW, Australia; Neuroscience Research Australia, Randwick, Sydney, NSW, Australia.
² 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.
³ 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.
⁴ Neuroscience Research Australia, Randwick , Sydney, NSW, Australia.
⁵ Department of Psychiatry, University of Melbourne , Parkville, VIC, Australia.
⁶ School of Psychiatry, University of New South Wales, Sydney, NSW, Australia; Neuroscience Research Australia, Randwick, Sydney, NSW, Australia; Schizophrenia Research Institute, Sydney, NSW, Australia.
⁷ Department of Psychiatry, University of Melbourne, Parkville, VIC, Australia; Molecular Psychopharmacology Laboratory, The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia.
⁸ Department of Psychiatry, University of Melbourne, Parkville, VIC, Australia; Schizophrenia Research Institute, Sydney, NSW, Australia.

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.