Ulcerative colitis is a painful inflammatory bowel disease that is frequently comorbid with psychiatric disorders like anxiety and depression. While the exact mechanisms remain unclear, the microbes in our gut, our microbiota, may be part of the connection between the brain and the gut. One of the risk factors for colitis, anxiety, and depression is the lack of a receptor called ERβ. So, researchers wanted to know how, or if, ERβ-deficiency impacts the gut in an induced model of colitis. Mice without ERβ had more severe colitis symptoms and stronger anxiety-like behaviors than mice with ERβ, and their gut microbiota was markedly different than that of mice with ERβ. Co-housing experiments allow mouse microbiotas to influence one another, and mice with ERβ that were co-housed with ERβ-deficient mice had more severe colitis and anxiety-like behaviors than those housed separately. Further tests found that expression of the protein ERBB4 is reduced in the hypothalamus of ERβ-deficient mice and that the hypothalamic- pituitary-adrenal (HPA) axis was hyperactivated. While more research is needed, these results suggest that the ERβ-induced gut microbiota imbalance plays an important role in colitis severity and that it contributes to the development of anxiety-like behaviors through the HPA axis.