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REVIEW ARTICLES: Andrei Szöke, Anca Trandafir, Marie-Estelle Dupont, Alexandre Méary, Franck Schürhoff, and Marion Leboyer Longitudinal studies of cognition in schizophrenia: meta-analysis The British Journal of Psychiatry 2008; 192: 248-257 [Abstract] [Full text] [PDF]

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How long is longitudinal

Ahmed S huda   (25 April 2008)

How long is longitudinal 25 April 2008
Ahmed S huda, Consultant, Early Intevention in Psychosis Pennine Care Trust Send letter to journal: Re: How long is longitudinal ahmed.huda{at}pennincare.nhs.uk Ahmed S huda	One of the authors' aims was to distinguish if cognitive deficits were progressive. They used studies which retested after at least one month. The means for half of the studies included retesting occurred btween 1-4 months but with a few "outliers" pulling the mean to 12 months. This is a relatively short period of time to deterimine if cognitive deficits are progressive. The data supplement did not state the period of time between tests for the studies. It suggests there were few studies included with retesting beyond 12 months. I think we can accept the autohrs' conclusions of improvement in cognitive testing. However we have to add the further caveat that this seems to be in the short term only (12 months or less given the likley paucity of data from after this period included in the study). This paper can not address the issue of whether schizophrenia is associated with progressive cognitve deficits in the long term as it does not include enough studies with time between tests measured in years/ decades. For example: V. S. Gabrovska-Johnson et al (2003),"Right-hemisphere encephalopathy in elderly subjects with schizophrenia: evidence from neuropsychological and brain imaging studies" Psychopharmacology Volume 169, p. 367-375 found evidence of neurocognitive deficits in elderly patients with schizophrenia that were different than those found in Alzheimer's disease. Perhaps the authors' were too restrictive in their entry criteria and excluded a lot of the longer term studies. It would be unfortunate if the authors' study was to be referenced in future as proof that there is no long term cognitive deteriotation in schizophrenia.