Gray and White matter microstructural alterations in major depressive disorder: a multi-center diffusion imaging...

Area of Science:

• Neuroimaging
• Neuroscience
• Psychiatry

Background:

• Diffusion imaging, including diffusion tensor imaging (DTI), is crucial for studying brain microstructure in major depressive disorder (MDD).
• Previous DTI studies often focused on white matter (WM) and region-specific changes, with limited analysis of gray matter (GM) microstructural alterations using advanced models.
• A comprehensive assessment of widespread microstructural changes in MDD is needed.

Purpose of the Study:

• To investigate gray matter (GM) and white matter (WM) microstructural changes in MDD patients using neurite orientation dispersion and density imaging (NODDI) and DTI.
• To examine both whole-brain and regional microstructural alterations.
• To explore correlations between diffusion indices and clinical variables like illness duration and depression severity.

Main Methods:

• Employed NODDI and DTI techniques on data from 159 MDD patients and 112 healthy controls across multiple centers.
• Utilized gray matter-based spatial statistics (GMS) and tract-based spatial statistics (TBSS) for regional analyses.
• Assessed diffusion indices including free water fraction (FWF), orientation dispersion index (ODI), and fractional anisotropy (FA).

Main Results:

• MDD patients showed significantly increased FWF in GM, elevated ODI in WM, and decreased FA in WM compared to controls.
• WM FA negatively correlated with illness duration, while WM ODI positively correlated with illness duration.
• GMS identified increased FWF in frontal, temporal, and limbic regions; TBSS revealed widespread FA reductions in WM.

Conclusions:

• Microstructural tissue disorganization, characterized by increased GM water and altered WM integrity, may be integral to MDD pathophysiology.
• Diffusion imaging findings suggest widespread GM and WM alterations in MDD, extending beyond previously studied regions.
• Further research is required to elucidate the biological mechanisms underlying these neuroimaging findings in MDD.