Meta-analysis of thalamic size in schizophrenia.

BACKGROUND This article presents a meta-analysis of thalamic size reduction in schizophrenia. METHODS Reviewed studies were based on magnetic resonance imaging or postmortem material and included measures of thalamic volume or thalamic area in schizophrenic patients and comparison subjects. Meta-analysis I was based on absolute thalamic values (not controlled for overall brain size), and Meta-analysis II evaluated thalamic size adjusted for brain size. RESULTS Meta-analysis I included data from 15 studies (485 schizophrenic subjects and 500 control subjects). Twelve (80%) of the studies had negative effect sizes, which is consistent with the hypothesis that thalamic size is smaller in schizophrenic subjects compared to control subjects. The composite effect size was -0.29 (p <.0001; without outliers: -0.41, p <.0001). Meta-analysis II included data from 11 studies (313 schizophrenic patients and 434 control subjects). Ten (91%) of the studies had negative effect sizes. The composite effect size was -0.35 (p <.0001; without outlier: -0.30, p <.0001). CONCLUSIONS Both meta-analyses indicate a statistically significant, small-to-moderate effect size for thalamic size reduction in schizophrenia; however, the effect size for thalamic size reduction is modest in comparison to that of other structural abnormalities noted in schizophrenia.