Impact of early and recent stress on white matter microstructure in major depressive disorder

Background: Major Depressive Disorder (MDD) is a worldwide-spread pathology, characterized by lifetime-recurrent episodes. Adverse childhood experiences (ACE) increase the lifetime risk of developing depression and affect the structure of the brain. Recent stressful events (RSE) can trigger the onset of depressive episodes, and affect grey matter volume. The aim of our study is to analyse the effect of both early and recent stress events on white matter microstructure in MDD patients and healthy volunteers. Methods: Sixty-five MDD inpatients and fifty-nine healthy controls underwent MRI acquisition of diffusion tensor images with a 3.0 T scanner. Severity of ACE and RSE was rated, respectively, on the Risky Families Questionnaire and on the Social Readjustment Rating Scale. Results: A significant effect of diagnosis was observed, with MDD subjects showing reduced fractional anisotropy (FA) and axial diffusivity (AD) compared to healthy controls in all the major association, projection and commissural tracts. In patients with MDD, but not in healthy controls, both ACE and RSE correlated with measures of WM microstructure: ACE correlated negatively with AD and MD, whereas RSE correlated negatively with FA. Limitations: The two diagnostic groups differed for age and education, previous and current medications, and treatment periods. Conclusions. Exposure to both early and recent stress exerts a widespread effect on WM microstructure of MDD patients, with a different impact possibly depending from the developmental period in which the stress has occurred.