Meta-analysis of brain size in bipolar disorder

A recent meta-analysis concluded that patients with schizophrenia have redu ced cerebral volume, and this finding has been used to implicate neurodevel opmental events in the etiology of this disorder. Since bipolar-disorder pa tients and schizophrenia patients have some similar brain abnormalities, it was of interest to meta-analytically review the literature on brain size i n bipolar disorder. Only seven studies met the inclusion/exclusion criteria for our metaanalysis, but none reported the brain size differences between the bipolar patients and the controls to be statistically significant. The composite effect size was a negligible 0.04 (95% CI: -0.17 to 0.25) and st atistically not significantly different from 0.0 (no effect). Thus, it appe ars that bipolar disorder is not associated with the same cerebral volume r eductions noted in schizophrenia. Implications for hypotheses regarding the etiology of the two disorders are discussed. (C) 1999 Elsevier Science B.V . All rights reserved.