Excessive exposure of mice to stressors, such as immobilization and pathogens, stimulates the secretion of adrenal hormones, such as cortisol, and immune cytokines, such as IL-1β and IL-6, via the activation of the hypothalamus − pituitary − adrenal (HPA) axis, resulting in the occurrence of colitis and gut dysbiosis accompanied by anxiety, depression, and memory impairment8,10–12. Here, IL6 is linked to major depressive disorder.