Anatomical MRI study of corpus callosum in unipolar depression

Previous studies have suggested abnormal cerebral lateralization in major depressive disorder (MDD). Few controlled MRI studies have investigated the corpus callosum (CC), the largest commissura connecting the two cerebral hemispheres, in MDD. This study investigated anatomical abnormalities in the CC and its subdivisions in MDD patients. Twenty-two unmedicated MDD patients and 39 healthy subjects underwent brain magnetic resonance imaging (MRI). Measurements of the CC and its sub-regions were performed with a semi-automated software (NIH Image, version 1.62). ANCOVA with age, gender, and intra-cranial volume (ICV) as covariates showed no significant differences in CC measurements between patients and controls (df=1,56; p>0.05). However, patients with familial MDD had a significantly larger middle genu area (F(1,45)=4.252; p=0.045) compared to healthy controls, and significantly larger middle genu (F(1,13)=5.366; p=0.037), anterior splenium (F(1,13)=6.27; p=0.026), and middle splenium areas (F(1,13)=4.706; p=0.049) compared to patients with non-familial MDD. Although preliminary, our findings suggest that anatomical abnormalities in CC may be restricted to patients with familial MDD, with possible enlargement of CC in this particular sub-group. The possible role of callosal abnormalities in the pathogenesis of mood disorders should be further examined.