From Gut to Brain: How Microbiota Modulate Stress and Mental Health

Abstract

The microbiome is a collaborating microbial community that refers to the collection of microorganisms, their structural substances, genes, and metabolites that exist in a habitat, creating a separate community in many places, such as the human gut. They form a complex ecosystem that helps in homeostasis, digestion, nutrient uptake, energy production, vitamin synthesis, and immune and inflammatory modulation. They change in response to a variety of environmental factors, like exercise, diet, and medication. Dysbiosis, or microbiota imbalances, affects body functions and leads to a variety of diseases, making it an important area for management. Chronic abdominal symptoms are recently regarded as a dysregulation of the interactions between the gut, gut microbiome, enteric nervous system, and central nervous system; the gut-brain pathways, thereby affecting the patient’s behavior and attitude. In addition, the gut microbiota produces about 90% of serotonin. Therefore, dysbiosis of gut microbiota leads to cognitive and mood disorders. Chronic stress activates the brain to produce stress hormones that influence the gut microbiota, affecting gut peristalsis and intestinal permeability, which creates a hostile environment for beneficial microbiota, allowing the stress-resistant species to dominate. Moreover, it decreases the formation of essential metabolites such as short-chain fatty acids (SCFAs), which regulate inflammation and mood, increasing depression and anxiety, and leads to further stress and negative feedback, producing more vicious cycles.