Objective: Several mental disorders have been linked to imbalances in the diversity, composition, and function of the gut microbiota, regardless of the protection offered by the blood-brain barrier. This systematic review considered research that compared the gut microbial makeup of healthy volunteers and those with bipolar disorder, epilepsy, anxiety, and major depressive disorders (MDD).
Materials and Methods: To find human case-control studies and cohort-designed studies that examined the connections between mental health disorders and stool microbiota measurements, Medline via PubMed, Google Scholar, and Science Direct databases were searched using the phrases title: (Role of gut microbiota on mental health) AND title: (Role of gut microbiota on depression OR mental health OR anxiety).
Results: We analyzed the resulting research, concentrating on bacterial taxa that differed between MDD and healthy controls as well as between all recruited participants with psychiatric illnesses. Actinobacteria, Bacteroidetes, Firmicutes, Fusobacteria, Euryarchaeota, Proteobacteria, Spirochaetes, Nitrospirota, and Verrucomicrobia were among the nine phyla that were represented. Seven of these phyla were found to be significant in both case-controlled and cohort-designed studies, but studies for all phyla produced different results. Ten of the nine taxa had lower MDD, seven had findings in both directions for case-controlled studies, and eleven had higher MDD. Thirteen genera were found to be less abundant in the MDD and Anxious Distress groups, whilst 28 genera were found to be significantly abundant in both groups.
Conclusions: There is no specificity on the bacterial taxa most frequently associated with mental health disorders based on the human research of mental health disorders and gut microbiota that are currently available.