CXCR4 and depressive disorder: In this research, we found that the CXCR4 signaling pathway was activated in the liver of depression; however, there was no sufficient evidences to inference whether depression causes liver damage and then causes liver to activate CXCR4 signaling pathway for excitable liver protection or depression activated the CXCR4 signaling pathway in liver and strengthened the possibility of liver cancer; it deserves further research.