Studies on MDD have shown that the increase of some proinflammatory bacteria and the decrease of some anti-inflammatory bacteria in patients are related to inflammatory factors (IL-1β, IL-6, and TNF-α) and cognitive function, and intestinal microbiota may be responsible for cognitive impairment in patients with MDD (Liu P. et al., 2021). The gene discussed is IL6; the disease is Cognitive impairment.