The Gut-Brain Axis and Its Role in Depression.

The gut microbiota in humans communicates to the central nervous system through the gut-brain axis, and this communication functions in a bidirectional manner. The backbone of this axis is via the vagus nerve allowing the communication. Research on the functionality of the gut-brain axis is present; however, analysis of the diversity and stratification of the gut microbiota is in its infancy. Through the exploration of various studies focusing on the role of the gut microbiota and its effects on the efficacy of selective serotonin receptor inhibitors (SSRIs) in depression management, many promising alterations in constructive changes have emerged. It has become evident that a set of quantifiable microbial markers have been identified as consistent in the stools of depressive subjects that can be further used to determine the severity of disease progression - the presence of certain bacterial species being a common thread amongst the therapeutic bacteria for depression management. The vagus nerve's role in the gut-brain axis, which is vital to carry out any constructive alterations in the gut microbiota, has been strengthened through evidence of SSRIs depending on the vagus to execute therapeutic effects. This review will focus on the interaction between the diversity of the gut microbiota and investigate its link with depression.