CCR2 was the receptor for Ccl2 in neurons,[31] and it is a G protein‐coupled receptor that binds Gαi.[32] Recruitment of Ccl2 to CCR2 inhibited intracellular cAMP levels, which activates its downstream protein kinase A signaling pathway and plays a significant role in the development of depressive disorders.[33] Therefore, the Ccl2‐CCR2‐cAMP axis could be a potential machinery for the control of neuronal activities and the presence of depression. This evidence concerns the gene CCR2 and major depressive disorder.