DPP4 and major depressive disorder: We identified 29 Co-DEGs in IBD and MDD: ACSL1, AQP5, ATF3, DDR2, DPEP1, DPP4, DUOX2, MAPK1, MTDH, NOX1, PPARG, PRKCA, RPL8, SIRT3, SLC39A14, SNX4, VDAC2, WWTR1, CYBB, GOT1, ATG7, GABARAPL2, IL6, TBK1, TF, TGFB1, TIMM9, BECN1, and TRIM26.