Longitudinal studies of cognition in schizophrenia: meta-analysis.

BACKGROUND A wide range of cognitive deficits have been demonstrated in schizophrenia, but their longitudinal course remains unclear. AIMS To bring together all the available information from longitudinal studies of cognitive performance in people with schizophrenia. METHOD We carried out a meta-analysis of 53 studies. Unlike previous reviewers, we included all studies (regardless of the type of medication), analysed each variable separately and compared results with data from controls. RESULTS Participants with schizophrenia showed a significant improvement in most cognitive tasks. The available data for controls showed, with one exception (the Stroop test), a similar or greater improvement. Performance in semantic verbal fluency remained stable in both individuals with schizophrenia and controls. CONCLUSIONS Participants with schizophrenia displayed improvement in most cognitive tasks, but practice was more likely than cognitive remediation to account for most of the improvements observed. Semantic verbal fluency may be the best candidate cognitive endophenotype.