People with social phobia have a different biological composition of their intestinal microbiota. The intestinal microbiota could be related to the processing of social relationships that takes place in the brain.

Fecal microbiota transplants have emerged as an effective technique to understand how they can affect phenotypic changes in the recipient. The research carried out has also shown that these transplants can transfer psychological and physiological traits in cases of depression, anxiety comorbid with irritable bowel syndrome or schizophrenia, that is, it seems proven that the intestinal microbiota is capable of affecting the brain functioning.