Amygdala and regional volumes in treatment-resistant versus nontreatment-resistant depression patients

Abstract

Background: Although treatment-resistant and nontreatment-resistant depressed patients show structural brain anomalies relative to healthy controls, the difference in regional volumetry between these two groups remains undocumented.

Methods: A whole-brain voxel-based morphometry (VBM) analysis of regional volumes was performed in 125 participants' magnetic resonance images obtained on a 1.5 Tesla scanner; 41 had treatment-resistant depression (TRD), 40 nontreatment-resistant depression (non-TRD), and 44 were healthy controls. The groups were comparable for age and gender. Bipolar/unipolar features as well as pharmacological treatment classes were taken into account as covariates.

Results: TRD patients had higher gray matter (GM) volume in the left and right amygdala than non-TRD patients. No difference was found between the TRD bipolar and the TRD unipolar patients, or between the non-TRD bipolar and non-TRD unipolar patients. An exploratory analysis showed that lithium-treated patients in both groups had higher GM volume in the superior and middle frontal gyri in both hemispheres.

Conclusions: Higher GM volume in amygdala detected in TRD patients might be seen in perspective with vulnerability to chronicity, revealed by medication resistance.

Keywords: biological markers; bipolar disorder; brain imaging/neuroimaging; depression; treatment resistance.