The keywords were classified into 10 categories: gut microbiota, Hypothalamic-pituitary-adrenal (HPA) axis, bipolar disorder, probiotics, irritable bowel syndrome, Parkinson’s disease, NLRP3 inflammasome, metabolic syndrome, vagus nerve, and short-chain fatty acids (see Figure 7A). This evidence concerns the gene NLRP3 and irritable bowel syndrome.