Focusing on plasmatic biomarkers, MDEs in MDD and BD are associated with prolonged exposure to cortisol in response to stressors (30–32), higher levels of acute phase proteins, mainly C-reactive protein (CRP) (33, 34), complement components C3 and C4 (35–40), and pro-inflammatory interleukin-6 (IL-6) (34, 41–43), and altered metabolic profiles in terms of leptin-resistance induced hyperleptinemia (44, 45) and reduced adiponectin levels (46–50). Here, IL6 is linked to major depressive disorder.