PMCH and major depressive disorder: In addition to being associated with feeding behavior and energy homeostasis, MCH has also been shown to play an important role in the regulation of anxiety- and depression-related behaviors in stressed rats and mice, and blocking MCH receptor 1 has antidepressant and anti-anxiety effects in various animal models (Ludwig et al., 2001; Abbott et al., 2003; Hausen et al., 2016; Jiang and Brüning, 2018).