Meanwhile, chronic MDD was associated with the dysregulation of hypothalamus pituitary adrenal axis (HPAS), pro-inflammatory cytokines (tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6)), cardiometabolic (blood pressure regulation, glucose, and fat metabolism) systems, etc. (Kahl et al., 2017). Here, IL6 is linked to major depressive disorder.