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Annotation

Meier MH, Caspi A, Reichenberg A, Keefe RS, Fisher HL, Harrington H, Houts R, Poulton R, Moffitt TE. Neuropsychological Decline in Schizophrenia From the Premorbid to the Postonset Period: Evidence From a Population-Representative Longitudinal Study. Am J Psychiatry . 2013 Sep 13 ; PubMed Abstract

Comments on Paper and Primary News
Primary News: Forty-Year Study Reveals Patterns of Cognitive Decline in Schizophrenia

Comment by:  Angus MacDonald, SRF Advisor
Submitted 23 September 2013 Posted 23 September 2013

The Dunedin study is not only a rich and rare resource for testing developmental hypotheses, but it has also been mined with ingenuity and resourcefulness over the years by Avshalom Caspi, Terrie Moffitt, and their colleagues to provide a number of provocative findings. In this case, they use the continuity of the sample and its multiple-informant design to test a number of useful hypotheses about the development of cognitive impairments in schizophrenia. Their population-based cohort of over 1,000 children yielded 31 cases of tightly defined schizophrenia by age 38. (The fact that this is over 3 percent of the sample, the authors argue, is explained by the comprehensiveness of their methods, suggesting that lower epidemiological estimates may underrepresent lifetime population risks.)

Their findings provide a particularly clear example of a moderate, generalized deficit in cognitive ability well before the onset of illness that, after onset, leads to further declines in fluid, but not crystalized intelligence. The example is clear because it addresses the diagnostic...  Read more


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Primary News: Forty-Year Study Reveals Patterns of Cognitive Decline in Schizophrenia

Comment by:  James Gold, SRF Advisor
Submitted 25 September 2013 Posted 25 September 2013

The recent paper by Meier et al. is a powerful confirmation of several observations that have been in the literature for many years. First, cognitive impairment is evident from early in development in people who go on to develop schizophrenia. Second, there is a loss of intellectual function that occurs in those people at risk who later become ill. Third, this "illness-associated" impairment appears to maximally impact more "fluid" intellectual functions and largely spares "crystallized" forms of verbal knowledge (however, those functions are not fully spared, as there is evidence of subnormal performance levels from early in development).

Thus, what Meier et al. have shown is not new, but it is the first time that these key findings have all been demonstrated in the same subjects followed over time in a population-based sample. The inclusion of a group of depressed patients as well as a mild cognitive impairment control group are innovations that enhance confidence that this is an effect related to schizophrenia in particular rather than psychopathology or cognitive...  Read more


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Comment by:  James MacCabeAnthony S. David
Submitted 19 March 2014 Posted 20 March 2014
  I recommend this paper

The article by Meier and colleagues makes a significant contribution to the field. Studies with prospectively ascertained neuropsychological data spanning years before and after the onset of psychosis are rare and valuable. However, despite our admiration for the work and for the authors, we have the following criticisms of the paper.

First, we question why the authors chose to separate out about 19 percent of the healthy population and label them "mild cognitive impairment." These were normal individuals who happened to have an IQ in the low normal range. The effect was to artificially enhance the mean IQ of the remaining healthy group, thereby accentuating the differences between the healthy and schizophrenia groups.

Second, the prevalence of schizophrenia in the cohort, and by extrapolation, the city of Dunedin, is, by the authors' estimate, 3.7 percent. This would make Dunedin an extreme global hotspot. The literature cited describing variation in international rates of schizophrenia does give lifetime rates over the quotidian 1 percent, but this is for the...  Read more


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