Kim et al. (2015) 's study showed that stress can cause activation of MCH receptors in BLA, leading to defects in emotion-related behaviors. In addition, the levels of P-CamKII α in BLA of MCH KO mice were decreased, and they were able to recover from chronic stress (Kim and Han, 2016a). However, there are also studies that contradict the above results of anxiety induced by MCH, in which intranasal administration of MCH significantly reduced depression-like behaviors in stressed rats and mice (Oh et al., 2020). Here, PMCH is linked to major depressive disorder.