Dilip KC, M.D., Vidyulata Salunkhe, M.D., M.P.H., Bibodh Jung Karki, M.D., Amar Sutrawe, M.D., Steven Lippmann, M.D.

Many commensal microbiota inhabit the human body, most commonly on skin and in the gastrointestinal tract.  There are trillions of microorganisms in the intestine; the most frequent inhabitants of the gut are Firmicutes, Bacterioides, Proteobacteria, Actinobacteria, and Cyanobacteria (1). Microbial flora composition changes during the life cycle and influences many metabolic, structural, and histological functions of the body (2).

Genetics, environment, diet, infections, antibiotics, and probiotics affect microbiota (3). Probiotics are foods and medicinal that enhance beneficial, physiological flora life. A reduction in certain flora results in microbial imbalance, yielding production of short chain fatty acids associated with higher inflammation levels (3).

Intestinal flora have a role in neuropsychiatric conditions, like mood disorders, autism, schizophrenia, and Parkinson’s disease (4). The bidirectional communication system documented between the brain and gut bacteria is called the gut-brain axis (5). It is mediated by neural, endocrine, and immune pathways. Gut microbiota influence brain development and the brain interacts with the neuroimmune and neuroendocrine systems (6).  

Inflammation of the gut increases permeability that fosters release of inflammatory mediators and disturbs the gut microbiome. Elevated levels of cytokines TNF-α and monocyte chemoattractant protein increase permeability of the blood-brain barrier and yields dysfunctional effects. This impairs brain function and can lead to anxiety, depression, and/or memory loss. Conversely, mental disorders like depression induce neurochemical dysfunctions with neuroplastic and organizational changes (7). Individuals with gastrointestinal disorders are more prone to psychiatric illnesses (8,9).

Treatment of people using current guidelines often influence the composition of gut microbiota, and that can further affect patient outcomes. New diagnostic tools and personalized, microbiota-based therapies might mitigate deregulation of the gut-brain axis. An analysis of the microbiota role in mental health might help to develop microbiota-based therapies (10). A class of drugs called, psychobiotics, include beneficial bacteria reported to minimize gut-brain-axis disorders (11). Thus, treatment of gut-brain axis dysfunction could enhance mental illness interventions (12). 

Greater understanding of gut microbiota and factors leading to floral imbalance such as stress, diet, and antibiotics might aid at attenuating and/or treating psychiatric issues in patients.  Understanding gut-brain psychology could promote research into improved health outcomes.

References

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