White matter integrity deficit in treatment-naïve adult patients with major depressive disorder.

OBJECTIVES The fronto-limbic system plays critical roles in cognitive functions, including emotion. This is supported by recent reports in the studies of major depressive disorder using diffusion tensor imaging of the brain. This study examined white matter integrity and correlations to cognitive function in treatment-naive adult patients with major depressive disorder. METHODS Fractional anisotropy values, derived from diffusion tensor imaging, were compared in 18 treatment-naïve adult patients with major depressive disorder and 18 well-matched healthy controls by voxel-based analysis. Correlation of fractional anisotropy with performance of cognitive tests was also analysed. RESULTS Lower fractional anisotropy values in the bilateral medial frontal gyri, right subgyral frontal and temporal lobes, and left middle frontal and cingulate gyri were observed in patients than in controls. However, no correlation between mean fractional anisotropy values and cognitive scores was found. CONCLUSION These findings support the notion that deficit of white matter integrity in the fronto-limbic system may be the neural substrate of major depressive disorder.