In vivo imaging studies suggest functional abnormalities of the thalamus in adult patients with bipolar disorder, but the presence of anatomical abnormalities is controversial. Our objective in this study was to compare the thalamus volumes of children and adolescents with bipolar disorder versus healthy controls to determine whether any morphological abnormalities exist early in illness course. We studied 16 patients with bipolar disorder according to DSM-IV criteria (mean age+/-SD=15.5+/-3.4 years) and 21 healthy control subjects (mean age+/-SD=16.9+/-3.8 years). Blinded examiners measured thalamic gray matter volumes with a semiautomated technique. Analysis of covariance, with age, gender, and intracranial brain volume as covariates, revealed no significant differences in left and right thalamic volumes between patients with bipolar disorder and healthy controls. Our findings indicate there are no significant differences in thalamus size between children and adolescents with bipolar disorder and healthy comparison subjects, in contrast to available findings for schizophrenia and first-break psychosis. Any differences in thalamus size that may exist between patients with bipolar disorder and healthy controls must amount to small effect sizes.
