Furthermore, the pathophysiological mechanisms focused on were also different in both studies; in the anorexia study, the role of feeding regulating hormones, such as ghrelin and leptin, were assessed in seven studies, whereas in this review, neuropeptides (i.e., substance P and NK receptor) and 5-HT regulating enzymes (i.e., TPH and MAO-A) were focused on by more than seven studies. Here, TPH1 is linked to Anorexia.