Bai Shao extract can reduce the expression of L-tryptophan (TRP) catabolizing enzyme tryptophan 2,3-dioxygenase (TDO) in the liver of stress-induced depression-like mice.[19] In addition, extracts of Sheng Jiang and Gui Zhi can also reduce the expression of P53 and glutathione reductase genes in the brain of depression model rats, and upregulate the expression of glutathione peroxidase 1 gene, improving depression symptoms in rats.[20,21] But the specific mechanism of XJZT antidepressant effect is not yet clear. Here, TDO2 is linked to major depressive disorder.