Graduation Date


Document Type

Senior Thesis

Degree Name

Bachelor of Science



Department or Program Chair

Andrea Renwanz Boyle PhD, FNAP

First Reader

Patricia Harris PhD, RN


The human gut is populated with hundreds of types of bacteria and fungi. In North America, both intestinal and mood disorders are prevalent, presenting health problems that challenge health care professionals and patients alike. A scholarly literature review was conducted to explore this important relationship.

The investigation of the literature revealed that there is an association between gut health disorders and mood disorders, mainly anxiety and depression. This is due to bi-directionality between the brain-gut pathways, meaning that gastrointestinal health may have an effect on mental health and vice versa.

This connection between gut and mood can have substantial implications for the treatment of both GI and mental health patients. Probiotics, bacteria that are beneficial to the body, have grown in popularity as a gut health supplement and may have an effect on the brain. Studies were conducted to test whether specific gut flora have effects on mood.

There were many differences identified between the gut flora of those with and without major depressive disorder. Specific bacterium, such as Lactobacillus plantarum P8, Bifidobacterium longum NCC300, and Lactobacillus rhamnosus HN001; have undergone randomized, double-blind, placebo-controlled trials and have been found to decrease feelings of depression as well as anxiety. Different probiotic strains have different effects on the mind, and these findings may be among the newest avenues of prevention and/or treatment for depression and anxiety. The next step will be additional research to validate these findings.