Rapid antidepressant therapy has been shown to be related to the circadian rhythm, but the specific molecular pathways have not been clarified. Accumulating evidence shows that the mitogen-activated protein kinase (MAPK) pathway is involved in the mechanism of action of antidepressants, and can simultaneously modulate the circadian system. Wang et al. propose that the MAPK pathway is a common route through which various rapid antidepressants regulate circadian genes. In the cover image, the rat in the depressive-like state (left) has a disturbed circadian rhythm. In contrast, when the circadian rhythm is normalized via the MAPK pathway (right), the rat rapidly returns to a relatively normal mood state. See pages 66–76 . (Cover image provided by Xin-Ling Wang).