Evidence has shown that oxytocin regulates stress responses through reducing the activity of the hypothalamic–pituitary–adrenal axis [50], inhibiting the activation of the amygdala in response to negative stimuli [51], activating oxytocin receptor-expressing neurons in the key brain regions [52], regulating autonomic stress responses [53], attenuating inflammation [54], exhibiting consolation-like behavior toward distressed affiliative conspecifics [55, 56], seeking social support, and reducing anxiety and depression-related behaviors. This evidence concerns the gene OXT and major depressive disorder.