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.