Dimensions of intelligence in schizophrenia: evidence from patients with preserved, deteriorated and compromised intellect

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    Abstract

    There is a growing literature describing a subgroup of "high-functioning" people with schizophrenia who show preserved intellectual ability (IQ). A detailed characterisation of the cognitive abilities of this group may be important in targeting appropriate treatment, management and services for patients with schizophrenia. It is a widely held belief that variation in cognitive processing speed is the basis of individual differences in intelligence. The main objective of this study was to identify subgroups of schizophrenia patients with preserved (N = 45), deteriorated (N = 47) and compromised (N = 17) intellect in order to study whether these subgroups differ in specific cognitive abilities (e.g. executive functions) or in general cognitive processing speed, as measured with an inspection time (IT) task. The patients who displayed an average estimated premorbid IQ, with no evidence of IQ decline (premorbid-current IQ difference <10 points), were found to show better performance on measures of executive function (continuous performance task, verbal fluency) compared with patients in the deteriorated and compromised subgroups. Nevertheless, this represented significantly impaired performance relative to healthy controls. In contrast, the average inspection times of patients with preserved IQ were as slow as those obtained in the deteriorated or compromised groups, indicating that high functioning patients are impaired in terms of cognitive processing speed. Furthermore, the average IT for all schizophrenia groups was significantly slower than that of healthy controls. These findings suggest that high functioning patients with schizophrenia exhibit enduring cognitive difficulties that may impact on their ability to benefit from rehabilitation interventions. (C) 2004 Elsevier Ltd. All rights reserved.
    Original languageEnglish
    Pages (from-to)11-19
    JournalJournal of Psychiatric Research
    Volume39
    Issue number1
    DOIs
    Publication statusPublished - 2005

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    Intelligence
    Schizophrenia
    Aptitude
    Executive Function
    Task Performance and Analysis
    Individuality
    Rehabilitation

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    title = "Dimensions of intelligence in schizophrenia: evidence from patients with preserved, deteriorated and compromised intellect",
    abstract = "There is a growing literature describing a subgroup of {"}high-functioning{"} people with schizophrenia who show preserved intellectual ability (IQ). A detailed characterisation of the cognitive abilities of this group may be important in targeting appropriate treatment, management and services for patients with schizophrenia. It is a widely held belief that variation in cognitive processing speed is the basis of individual differences in intelligence. The main objective of this study was to identify subgroups of schizophrenia patients with preserved (N = 45), deteriorated (N = 47) and compromised (N = 17) intellect in order to study whether these subgroups differ in specific cognitive abilities (e.g. executive functions) or in general cognitive processing speed, as measured with an inspection time (IT) task. The patients who displayed an average estimated premorbid IQ, with no evidence of IQ decline (premorbid-current IQ difference <10 points), were found to show better performance on measures of executive function (continuous performance task, verbal fluency) compared with patients in the deteriorated and compromised subgroups. Nevertheless, this represented significantly impaired performance relative to healthy controls. In contrast, the average inspection times of patients with preserved IQ were as slow as those obtained in the deteriorated or compromised groups, indicating that high functioning patients are impaired in terms of cognitive processing speed. Furthermore, the average IT for all schizophrenia groups was significantly slower than that of healthy controls. These findings suggest that high functioning patients with schizophrenia exhibit enduring cognitive difficulties that may impact on their ability to benefit from rehabilitation interventions. (C) 2004 Elsevier Ltd. All rights reserved.",
    author = "Johanna Badcock and Milan Dragovic and Flavie Waters and Assen Jablensky",
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