Enlargement of the amygdala in patients with a first episode of major depression

Background: The amygdala plays a crucial role in the mediation of affective behavior in humans and is implemented in the limbic-thalamic-cortical network that is supposed to modulate human mood. The aim of the present study was to measure the amygdala volumes in patients with a first episode of major depression. Methods: Thirty inpatients with a first episode of depression were compared with 30 healthy volunteers matched for age, gender, handedness, and education by performing structural magnetic resonance imaging (MRI) measures of the amygdala. Results: Patients showed increased amygdala volumes in both hemispheres as compared to healthy control subjects. No significant correlations were found between amygdala volumes and age, age of onset, illness duration, or severity of depression in the patient group. Conclusions: Enlarged amygdala volumes in patients with a first episode of major depression might be due to enhanced blood flow in the amygdala rather than to a neurodevelopmental structural predisposition to major depression.