Quantitative MRI of the hippocampus and amygdala in severe depression

Background. There is little evidence to support possible structural changes in the amygdala and hippocampus of patients with severe depression. Methods. Quantitative MRI of the amygdala and hippocampus, as well as proto n spectroscopy (MRS) of mesial temporal structures were studied in 34 drug- resistant in-patients with major depression and compared with 17 age-matche d controls. Volumetric MRI data were normalized for brain size. Results. The volume of the left hippocampus was significantly smaller in th e patients compared with the controls. Both groups exhibited similar signif icant hippocampal asymmetry (left smaller than right). The patients, but no t the controls, had significant asymmetry of the amygdalar volumes (right s maller than left). No differences were observed between the patients and co ntrols in the T2 relaxation times for the hippocampus and amygdala. Mesial temporal lobe MRS revealed a significantly elevated choline/creatine ratio in the patients compared with the controls. Conclusions. This quantitative MRI study provides support for a possible as sociation between structural and biochemical substrates and severe drug-res istant major depression.