Background: Schizophrenia is characterized by a generalized cognitive impairment with pronounced deficits in the domains of verbal memory, executive functioning and attention.
Aim: To investigate whether cognitive deficits found in patients with schizophrenia are also found in non-affected relatives.
Method: A meta-analytic review of the published literature on cognitive performance between relatives of schizophrenic patients and healthy controls.
Results: The meta-analyses yielded nine weighted effect sizes from 37 studies comprising 1639 relatives of schizophrenia patients and 1380 control subjects. The largest differences were found on verbal memory recall (d=0.54, 95% CI=0.43-0.66) and executive functioning (d=0.51, 0.36-0.67). Attentional functioning showed smaller effect sizes (d=0.28, 0.06-0.50). These effect sizes are in the moderate range.
Conclusion: Cognitive deficits found in patients with schizophrenia are also found in non-affected relatives. This finding is consistent with the idea that certain cognitive deficiencies in relatives are caused by familial predisposition to schizophrenia and that these deficiencies might be putative endophenotypes for schizophrenia. However, our results do not address genetic causes directly. Further work is needed to determine whether certain cognitive traits are familial and whether there is co-inheritance of these traits with schizophrenia within families.