Aberrant levels of cortical myelin distinguish individuals with unipolar depression from healthy controls

The association of unipolar depression (UD), relative to healthy controls (HC), with cortical myelin is underexplored, despite growing evidence of associations with white matter tract integrity. We characterized cortical myelin in the 360 Glasser atlas regions using the T1w/T2w ratio in 39 UD and 47 HC participants (ages=19-44, 75% female). A logistic elastic net regularized regression with nested cross-validation and a subsequent linear discriminant analysis conducted on held-out samples were used to select brain regions and classify UD vs. HC. True-label model performance was compared against permuted-label model performance. Cortical myelin distinguished UD from HC with 68% accuracy (p<0.001; sensitivity=63.8%, specificity=71.5%). Brain regions contributing to this classification performance were located in the orbitofrontal cortex, anterior cingulate, extended visual, and auditory cortices, and showed statistically significant decreases and increases in myelin levels in UD vs. HC. The patterns of cortical myelin in these regions may be a biomarker of UD.