Certain intestinal peptides, including peptide YY (PYY), glucagon-like peptide-1 (GLP-1), cholecystokinin, CRH, growth inhibitory-releasing peptide, and oxytocin, are especially important, as they modulate depressive and anxiety-related behaviors (Młynarska et al., 2022; Dockray, 2014). The gene discussed is PYY; the disease is Anxiety.