IL6 and major depressive disorder: Associations were found between child abuse and/or neglect, depression, perceived stress, fatigue, and plasma levels of cytokines interleukin (IL-6), C-reactive protein (CRP), soluble tumor necrosis factor receptor type II (sTNF-RII), interleukin IL-1 receptor antagonist (IL-1ra), and psycho-physiological adjustments that may lead to BC.