Executive deficits in Individuals at High Genetic Risk of Schizophrenia
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Background. Studies of individuals at high genetic risk (HR) of schizophrenia have shown subtle deficits in the domains of executive functions. However, executive abilities also depend on working memory, which is one of the most prominent impairments associated with vulnerability to schizophrenia. The present study examines whether working memory deficits could account for impairments usually attributed to executive dysfunctions. Methods. A total of 100 HR and 27 control participants were assessed on working memory and executive tasks. Linear regressions were applied to compare neuropsychological performance between the two groups and to examine the contribution of working memory to performance on those executive tasks where significant difference was evident. Results. HR individuals had significantly reduced working memory capacity and manipulation. Impairments were also found in processing speed, set-shifting and planning abilities. After accounting for the contribution of working memory, the HR group did not significantly differ from controls on cognitive flexibility and planning, however the group differences on processing speed and set-shifting remained significant. Conclusion. Cognitive flexibility and planning processing speed impairments found in HR could be attributed to deficits in working memory processing rather than deficits in pure executive domains. Perceptual processing speed and set-shifting may represent affective endophenotypes characterising genetic predisposition to schizophrenia, independent from working memory impairments.