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General intellectual ability does not explain the general deficit in schizophrenia.

ABSTRACT: Patients with schizophrenia demonstrate a generalized deficit across multiple cognitive domains. However, it is unknown whether this deficit is largely due to lower intelligence, or if there is an impact of schizophrenia which cannot be accounted for by measures of general intellectual ability (GIA). We created four IQ-matched strata of equal width between 89 healthy volunteers (HC) and 77 patients with schizophrenia (SZ) who had very similar IQ and reading scores within each stratum, then compared each stratum's performance on the MATRICS Consensus Cognitive Battery (MCCB). We hypothesized that any patient impairment on the MCCB after matching on IQ would be evidence that GIA does not fully explain the general deficit seen in schizophrenia. We found that patients showed evidence of greater neuropsychological impairment than what would be expected based solely on their IQ and reading ability scores. Further, this deficit was stronger in some cognitive domains than others, namely, processing speed and social cognition. These results suggest the presence of a distinction between GIA and generalized neuropsychological impairment that was consistent in magnitude across all patients, regardless of IQ.

SUBMITTER: Gray BE

PROVIDER: S-EPMC3679318 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature

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General intellectual ability does not explain the general deficit in schizophrenia.

Gray Bradley E BE McMahon Robert P RP Gold James M JM

Schizophrenia research 20130509 2-3

Patients with schizophrenia demonstrate a generalized deficit across multiple cognitive domains. However, it is unknown whether this deficit is largely due to lower intelligence, or if there is an impact of schizophrenia which cannot be accounted for by measures of general intellectual ability (GIA). We created four IQ-matched strata of equal width between 89 healthy volunteers (HC) and 77 patients with schizophrenia (SZ) who had very similar IQ and reading scores within each stratum, then compa ...[more]

PMID: 23664590

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Project description:There has been a long argument over whether schizophrenia is a neurodegenerative disorder associated with progressive cognitive impairment. Given high heritability of schizophrenia, ascertaning if genetic susceptibility to schizophrenia is also associated with cognitive decline in healthy people would support the view that schizophrenia leads to an accelerated cognitive decline. Using the population representative sample of 6817 adults aged >50 years from the English Longitudinal Study of Ageing, we investigated associations between the biennial rate of decline in cognitive ability and the schizophrenia polygenic score (SZ-PGS) during the 10-year follow-up period. SZ-PGS was calculated based on summary statistics from the Schizophrenia Working Group of the Psychiatric Genomics Consortium. Cognition was measured sequentially across four time points using verbal memory and semantic fluency tests. The average baseline verbal memory was 10.4 (SD = 3.4) and semantic fluency was 20.7 (SD = 6.3). One standard deviation (1-SD) increase in SZ-PGS was associated with lower baseline semantic fluency (β = -0.25, 95%CI = -0.40 to -0.10, p = 0.002); this association was significant in men (β = -0.36, 95%CI = -0.59 to -0.12, p = 0.003) and in those who were aged 60-69 years old (β = -0.32, 95%CI = -0.58 to -0.05, p = 0.019). Similarly, 1-SD increase in SZ-PGS was associated with lower verbal memory score at baseline in men only (β = -0.12, 95%CI = -0.23 to -0.01, p = 0.040). However, SZ-PGS was not associated with a greater rate of decline in these cognitive domains during the 10-year follow-up. Our findings highlight that while genetic susceptibility to schizophrenia conveys developmental cognitive deficit, it is not associated with an ongoing cognitive decline, at least in later life. These results do not support the neo-Kraepelinian notion of schizophrenia as a genetically determined progressively deteriorating brain disease.

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General intellectual ability does not explain the general deficit in schizophrenia.

Publications

General intellectual ability does not explain the general deficit in schizophrenia.

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