<span style="font-family:Verdana;">The effects of microorganisms on the central nervous system are manifested in both health and disease states. The symbiotic microorganisms in the human gut have certain effects on the brain development before and after birth. Chronic inflammation in patients with irritable bowel syndrome (IBS), psychiatric disorders such as PTSD, anxiety disorders, etc., is likely to be associated with an imbalance in gut flora. Intestinal flora regulates the central nervous system mainly through nerve, endocrine, metabolic and immune pathways. The mechanisms involved in the influence of intestinal flora on the central nervous system are diverse, so it is necessary to explore the role of intestinal flora in mental and psychological diseases.</span>