PMCH and major depressive disorder: Indeed, ICV infusion of MCH peptide, or local infusion into mood-regulating brain structures, are widely reported to induce/enhance anxiety and depression-like behaviors in rodents (Georgescu et al., 2005; Lagos et al., 2011b; López Hill et al., 2013; Urbanavicius et al., 2014, 2016, 2019; Ye et al., 2018; see Figure 1), though a few early (Monzón and De Barioglio, 1999; Monzón et al., 2001), and one more recent (Oh et al., 2020), studies reported an anxiolytic or antidepressant effect.