Depression is a mental health disorder that affects 5% of the population, however, 60% of patients do not respond to currently available antidepressants. While it can be argued that a variety of causes contribute to depression, many studies have shown correlations between the structure and composition of the gut microbiome and depressive disorders. Furthermore, the gut microbiome produces metabolic products that contribute to depression. This review will discuss the gut microbiome composition and associated metabolic products that may contribute to the severity of depression, as well as current and potential treatments and their effects on the gut microbiome composition. While individual gut composition can vary, depressed individuals appear to have lower abundances of Faecalibacterium, Escherichia, Ruminococcus,

Eubacterium, Clostridium, Lachnospiraceae, and Bifidobacterium, in comparison to non-depressed individuals. These bacteria contribute in part to the overall neuroactive metabolic production of serotonin, dopamine, GABA, norepinephrine, butyric acid, tryptophan, and tyrosine. Current treatments for depression are not effective for all and do not address the treatment of gut dysbiosis. Treating depression as a symptom of dysbiosis may be worthwhile. There is potential for the treatment of depression using alternative medicine, probiotics, and fecal microbiota transplant, which directly addresses the gut microbiome.