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 proton spectroscopy
(MRS) of mesial temporal structures were studied in 34 drug-resistant in-patients with major
depression and compared with 17 age-matched controls. Volumetric MRI data were normalized for
Results. The volume of the left hippocampus was significantly smaller in the patients compared
with the controls. Both groups exhibited similar significant hippocampal asymmetry (left smaller
than right). The patients, but not the controls, had significant asymmetry of the amygdalar volumes
(right smaller than left). No differences were observed between the patients and controls 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 association between
structural and biochemical substrates and severe drug-resistant major depression.