Corpus callosum size and shape in individuals with current and past depression

Background: The corpus callosum enables the efficient linking of the two cerebral hemispheres. Reductions in the size of the anterior callosum have been described in geriatric depression, although findings in young adults have been much more equivocal.
Methods: Data was acquired in 26 currently depressed (mean age 32.15 years, 5/26 male) and 28 remitted non-geriatric adults (mean age 36.36 years, 7/28 male), and 32 control subjects (mean age 34.41 years, 11/32 male). The total area, length and curvature of the callosum, and regional thickness along 39 points, from a mid-sagittal T1-weighted magnetic resonance image were compared across the groups.
Results: Total area, length and curvature did not differ between the groups. The currently-depressed group showed expansions in the thickness of the posterior body and isthmus when compared to controls; this was not seen in remitted patients. Similar expansions were seen when comorbidly anxious patients were compared to depressed patients without anxiety. There was no difference between melancholic and non-melancholic patients, and medication status did not affect the results.
Limitations: Currently-depressed patients showed higher rates of co-morbid anxiety and medication usage than remitted patients, although in the depression group as a whole there was no difference between medicated and unmedicated patients.
Discussion: The corpus callosum shows expansions in regions connecting frontal, temporal and parietal regions in currently depressed patients only, suggestive of state-related changes in white matter in major depression that may reflect the effects of state-related factors on white matter structure.