SHMT2 and major depressive disorder: For anxiety or depression, individual indices WBC, platelets, neutrophils, CRP, GlyA and composite indices NLR, SII, SIRI, INFLA all showed significant mediating effects, with intermediate ratios of 3.13, 1.85, 4.84, 6.68, 5.86, and 3.52%, 4.55, 4.06, 9.00%, respectively.