Accordingly, we propose an experimental approach for NFKB, OPRM1, and EGFR, as central nodes in our network analysis, they can be explored in experimental and clinical studies in MDD: NFKB via peripheral blood mononuclear cells or inflammatory markers (e.g., TNF-α, IL-6) [73], OPRM1 via accessible cells or genetic polymorphisms [74], [93], and EGFR via soluble EGFR or plasma EGF [75]. This evidence concerns the gene OPRM1 and major depressive disorder.