MAPK1 has not only been shown to be downregulated in PFC of depressed subjects51, 52 and in the frontal cortex of chronic restraint rats53 but its downregulation can lead to depressive phenotype in rodents.54 Phospholipase D, whose roles in cell communication and a wide range of biological processes are well demonstrated and whose expression is compromised in rat model of depression,55 is the target of miR-324-5p. Here, MAPK1 is linked to major depressive disorder.