Volumetric asymmetries in late-onset mood disorders: an attenuation of frontal asymmetry with depression severity.

The purpose of the study was to examine global and regional volumetric asymmetries in patients with late-onset mood disorders and non-depressed control subjects. Our sample comprised 34 patients with late-onset major depression, 18 patients diagnosed with late-onset minor depression and 30 control subjects. All subjects were scanned using a 1.5 Tesla GE Scanner, and quantitative estimates of global and focal brain volumes were obtained. Control subjects and patients displayed significant right-left volumetric differences across several regions, with right-sided regions being larger than the left. In the frontal lobes, the asymmetry differed significantly in the three groups (P=0.02). It was most pronounced in the control group and decreased significantly in the minor and major depression groups. There was a significant trend (P=0.005) in the magnitude of frontal asymmetry across groups, with the frontal asymmetry decreasing with increasing severity of depression. Hemispheric and temporal asymmetries were comparable in all three groups. These data suggest that an attenuation of the 'normal' volumetric asymmetry in the frontal regions may provide a structural basis to late-onset mood disorders