In comparison with simple MDD, MDD with melancholic and psychotic features and suicidal behaviors are reported to be associated with increased pro-inflammatory markers, namely APPs (e.g., haptoglobin), upregulated T cell markers, besides failure to suppress the production of IL-1β and sIL-2R by administration of dexamethasone [2,17,18,19,20]. Here, CTSB is linked to major depressive disorder.