For example, ghrelin was reported to both promote (Carlini et al., 2002, 2004; Hansson et al., 2011; Currie et al., 2012; Spencer et al., 2012; Meyer et al., 2014) and alleviate (Lutter et al., 2008; Spencer et al., 2012; Jensen et al., 2016; Huang et al., 2017) anxiety- and depression-like behaviors, a dual but disparate effect which may depends on both contextual states (for example, non-stress vs. stress, acute vs. chronic stress, mild vs. strong stress) and physiological states (for example, food availability) of the animal (Spencer et al., 2015). This evidence concerns the gene GHRL and Anxiety.