In depression, (1) the inflammatory processes including IL-6 stimulate the release of corticotrophin-releasing hormone (CRH) and heighten hypothalamic-pituitary-adrenal axis activity, which leads to elevated cortisol levels to initiate and/or worsen symptoms of depression [32,33]; (2) central and peripheral administration of IL-6 influences mood states [34]; (3) levels of IL-6 decreases in responders to antidepressant treatment, while it remains high in nonresponders [35,36]. Here, CRH is linked to major depressive disorder.