In general, amygdala removal after surgery can cause a variety of psychological and physiological stresses, including postoperative pain, leading to an imbalance of the HPA axis, rising levels of CRH and GC, and disorders in the signal transmission of serotonin (5-HT) and norepinephrine (NE), creating a physical, emotional and psychological burden that may eventually accumulate into symptoms of mental illnesses such as depression and anxiety. Here, CRH is linked to major depressive disorder.