Is deterioration of IQ a feature of first episode psychosis and how can we measure it?

Abstract Estimates of pre-morbid IQ are widely used to measure the trajectory of cognitive function and decline in people with schizophrenia. This study examined the usefulness of two indices of decline to identify cognitive subtypes in first episode psychosis, and to determine the specificity of no...

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Bibliographic Details
Published in:Schizophrenia research 2012-05, Vol.137 (1), p.104-109
Main Authors: O'Connor, Jennifer A, Wiffen, Benjamin D.R, Reichenberg, Abraham, Aas, Monica, Falcone, M. Aurora, Russo, Manuela, Sood, Poonam Gardner, Taylor, Heather, David, Anthony S
Format: Article
Language:English
Subjects:
Adolescent
Adult
Adult and adolescent clinical studies
Aged
Analysis of Variance
Biological and medical sciences
Cognition Disorders - diagnosis
Cognition Disorders - etiology
Executive Function
Female
Humans
Intellectual Disability - diagnosis
Intellectual Disability - etiology
Intelligence decline
Intelligence Tests
Male
Medical sciences
Memory
Memory neuropsychological function
Middle Aged
Neuropsychological Tests
Pre-morbid indices
Psychiatric Status Rating Scales
Psychiatry
Psychology. Psychoanalysis. Psychiatry
Psychopathology. Psychiatry
Psychoses
Psychotic Disorders - complications
Psychotic Disorders - diagnosis
Reading
Regression Analysis
Retrospective Studies
Schizophrenia
Verbal Learning
Young Adult
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Summary:Abstract Estimates of pre-morbid IQ are widely used to measure the trajectory of cognitive function and decline in people with schizophrenia. This study examined the usefulness of two indices of decline to identify cognitive subtypes in first episode psychosis, and to determine the specificity of non-IQ neuropsychological impairments in this population. Neuropsychological data were collected from 118 first episode psychosis patients and compared to 118 epidemiologically matched controls. The National Adult Reading Test (NART) and the Information subtest of the WAIS-III were compared as indicators of crystallised intelligence or ‘pre-morbid IQ’. Measurement of NART minus current full scale IQ (FSIQ) (where 10 points discrepancy is the decline criterion) did not reveal a large group of individuals with ‘deteriorating’ IQ patterns. Using the Information subtest and the same decline criteria, a ‘deteriorating’ patient group emerged (36%) but was matched by a larger ‘deteriorating’ control group (45%). The ‘deteriorating’ patient group performed at a low IQ level for tasks that loaded highly on performance ability but a relatively high level for tasks measuring verbal skills. Verbal memory discriminated patients from controls better than IQ. Compared to controls, patients showed large selective impairments of verbal episodic memory (effect size, d = 1.4) These data suggest that in first episode populations, caution should be exercised in inferring deterioration of IQ from discrepancies between reading-based and other IQ tests. Rather, sub-groups of patients and controls do show greater verbal aptitude in comparison to performance skills. Memory is generally impaired in first episode patients regardless of IQ.
ISSN:0920-9964
1573-2509
DOI:10.1016/j.schres.2012.01.041