Date of Award

Spring 2023

Document Type

Scholarly Project

Degree Name

Master of Physician Assistant Studies (MPAS)


Physician Assistant Studies

First Advisor

Kauffman, Russell

Second Advisor

Stavetig, Mindy


Depression, Major Depressive Disorder, Gut-Brain-Axis, Gut Microbiota, Probiotics


Major Depressive Disorder (MDD) is a crippling condition that affects millions of people worldwide. Serotonin reuptake inhibitors (SSRIs) are the staple treatment adjunct to psychotherapy. Recently, the connection between gut health, specifically the gut brain axis, has been researched to look at the connection between gut microbiota and it’s effect on depressive symptoms. A literature review was performed using electronic databases such as PubMed, PsychINFO, and embase. This meta-analysis evaluates the connection between gut microbiota and depression as well as the effectiveness of SSRI therapy on depression. Results show a significant change in gut microbiota with short term change to a Mediterranean diet (MD) compared to a Western diet (WD). This change in gut microbiota has also shown improvement in depressive symptoms. This analysis also found a link to degradation of the hypothalamus from certain gut bacteria found in a WD. SSRI therapy showed minimal improvement in depressive symptoms short term, with little increase in effectiveness long term.