background In the last years several studies reported on lateralization in schizophrenia. Results of these studies are equivocal.
aim To review studies on lateralization in schizophrenia.
method Meta-analysis of studies on hand preference, anatomical asymmetry and dichotic listening in schizophrenia. Studies were found by searching Medline and Psychlit and using cross references. results In 16 studies on handedness we find a mean weighted odds ratio for non-right-handedness in schizophrenia of 2.15 (95% confidence interval: 1.54-2.71). At meta-analysis 22 studies on anatomical asymmetry show that the hemispheres are significantly less asymmetric in schizophrenia and that there is more frequently a reversal of asymmetry. Meta-analysis of 10 dichotic listening studies shows no clear difference between schizophrenic patients and controls. When only studies with phonemes or rhyme words are considered, patients show significantly decreased language lateralization.
conclusion Meta-analysis of the literature of the past ten years provides evidence for increased prevalence of non-right-handedness, decreased anatomical asymmetry and decreased functional lateralization on dichotic listening tests in schizophrenia. These three findings indicate a lacking development of hemispheric specialisation.