The integrative analysis of the bioinformatics and ML identified 10 potent MDD-related biomarkers including CEACAM8, CLEC12B, DEFA4, HP, LCN2, NRG1, OLFM4, SERPING1, TCN1 and THBS1, that showed the most significant and strong differential expression between MDD patients and HCs. This evidence concerns the gene OLFM4 and major depressive disorder.