PYY and Anxiety: While early studies suggest that PYY and GLP-1 are expressed in several brain regions,215–218 including the nucleus tractus solitarius (NTS), a primary projection area for the vagus nerve,215 these hormones have been associated with reward processing, anti-anxiety and antidepressant effects, and enhancements in memory and neuroplasticity.219–223 However, further research is required to verify whether PYY is produced outside the GIT.