RELATIONSHIP BETWEEN THE CORTICAL THICKNESS AND SERUM CORTISOL LEVELS IN DRUG-NAÏVE, FIRST-EPISODE PATIENTS WITH MAJOR DEPRESSIVE DISORDER: A SURFACE-BASED MORPHOMETRIC STUDY

In major depressive disorder (MDD) patients, higher morning cortisol levels due to a hyperactive hypothalamic-pituitary-adrenal (HPA) axis have been reported. The aim of the present study was to evaluate the relationship between cortical thinning and the serum cortisol levels during the first depressive episode in drug-naïve MDD patients using an automated surface-based morphometry (SBM) method.

The institutional review board approved this prospective study. MR imaging data were obtained using a 3T scanner by a three-dimensional fast-spoiled gradient recalled acquisition with steady state (3D-FSPGR). Thirty drug-naïve patients with MDD and 41 age- and gender-matched healthy subjects (controls) were enrolled. We then used the SBM method (Freesurfer) to generate cortical thickness maps, and measured the cortical thickness in each subject. Morning blood samples were drawn from all participants for cortisol measurements.

We found the serum cortisol levels were significantly higher in the MDD patients than in the controls. The MDD patients manifested significant thinning of the left lateral orbitofrontal cortex compared with the controls. There was a significant negative linear correlation between the thickness of the left lateral orbitofrontal cortex and the serum cortisol levels in the MDD patients.

In the early stage of MDD, the thickness of the lateral orbitofrontal cortex was significantly reduced, and also showed a significant inverse correlation with the serum cortisol levels. Since the lateral orbitofrontal cortex contains a high concentration of glucocorticoid receptor, glucocorticoid receptor-mediated signaling transductions could contribute to neurotoxicity, which might occur when there are high cortisol levels in patients with MDD.