The microbiota–gut–brain axis is believed to modulate various central processes through the vagus nerve as well as production of microbial metabolites and immune mediators which trigger changes in neurotransmission, neuroinflammation, and behavior.

Little is understood about the utilization of microbiome manipulation to treat disease.

Though studies exploring the role of the microbiome in various disease processes have shown promise, mechanisms remain unclear and evidence-based treatments for most illnesses have not yet been developed.

The animal studies reviewed here offer an excellent array of basic science research that continues to clarify mechanisms by which the microbiome may affect mental health.

In this review, we focus on recent studies investigating the relationship between gut microbiome dysbiosis and the pathogenesis of depression.