In conclusion, we have shown that fractional anisotropy value of the left dorsomedial thalamus was significantly decreased for both medicated and unmedicated patients with major depression disorder, while plasma leptin secretion was enhanced and significantly correlated with FA value for only the latter, indicating that the microstructural abnormality of the white matter found in MDD patients is associated with high leptin levels. Here, LEP is linked to major depressive disorder.