Cerebral cortical thickness after treatment with desvenlafaxine succinate in major depressive disorder.

Thickness of the cerebral cortex has been previously investigated for its potential as a biomarker in major depressive disorder (MDD). This is the first study to examine the longitudinal effects of a serotonin-norepinephrine reuptake inhibitor, desvenlafaxine succinate (DVS), on whole-brain cortical thickness (CT) in patients treated for MDD. We also aimed to replicate a previous finding of an association between improvement in clinical severity and CT in one of five predefined regions-of-interest (ROI). Twenty-five individuals with MDD received treatment with DVS (50 mg/day) for 8 weeks, with 19 completing the study. We used FreeSurfer 6.0 to compare group differences between MDD and controls (n=23) and between treatment responders, treatment nonresponders and controls. We tested correlations between 8-week change in depression severity and regional CT in five ROIs: the rostral and caudal anterior cingulate cortex, lateral and medial orbitofrontal cortex and inferior temporal gyrus. There were no differences in CT between MDD and controls or DVS responders and controls. There was greater CT in DVS nonresponders in the left pars orbitalis when compared to controls [MNI (X, Y, Z=-38.4, 37.6, -11.1); P=0.027]. There were no significant correlations between change in depression severity and CT in any of the five ROIs. Brain CT does not seem to be a sensitive marker of short-term antidepressant response in MDD, except increased CT in nonresponders. Duration of the intervention and interindividual heterogeneity may impede identification of discriminating features of treatment response as associated to CT.