Limbic gray matter increases in response to cognitive-behavioral therapy in major depressive disorder

Abstract

Major depressive disorder (MDD) is related to volumetric decreases in (cortico-)limbic brain regions. In contrast to pharmacological and electroconvulsive therapy, little is known about the brain structural effects of psychotherapy and potential links to symptom improvements. In a naturalistic longitudinal study using structural magnetic resonance tomography, gray matter volume (GMV) and clinical measures were assessed in 30 outpatients with MDD before and after 20 cognitive-behavioral therapy (CBT) sessions. Data from 30 healthy controls was acquired. Region-of-interest analyses revealed significant GMV increases within patients for the right anterior hippocampus and the bilateral amygdala, resulting in a significant group-by-time interaction for the left amygdala (p ≤ 0.022). Simultaneously, analyses revealed volumetric decreases in the right posterior hippocampus (p = 0.016). While there were no associations with overall symptom improvement, right amygdala volume increases were slightly associated with improvements in identifying feelings (r_s = 0.321, p = 0.042). Together, findings show an impact of CBT not only on psychopathology but also on brain structure. The connection between CBT-related increased amygdala GMV and improved emotion identification emphasizes the role of improvements in emotional awareness.

Fig. 1. GMV changes in the amygdala within patients and the association with improvements in alexithymia (Difficulty Identifying Feelings).

Left: Scatter plots depicting GMV changes (∆ = t2-t1) within the cluster of the right amygdala (x = 32, y = −3, z = −27) on the y-axis correlated with changes (∆ = t1-t2) in the Toronto Alexithymia Scale (TAS20) subscale Difficulty Identifying Feelings (DIF; r_s = 0.321, p = 0.042) on the x-axis within the patient group. Line: regression slope. Right: Coronal view (Montreal-Neurological-Institute coordinate y = 0) depicts the results of the paired t-tests (t1 vs. t2) in the patient group within the bilateral amygdala.