Since changes in Gal-9, IFNγ, and Ido1 expression have been independently linked to central diseases such as depression and MS (2, 32, 34, 63), the ability of Gal-9 to accentuate DO expression during neuroinflammation may play a significant role in these and other psychiatric conditions and should be further studied as a putative therapeutic target. This evidence concerns the gene IDO1 and major depressive disorder.