We read with great interest the recent excellent work by Stevens et al,1 in which the authors showed that zonulin and fatty acid-binding protein 2 have a relationship with the increase in lipopolysaccharide (LPS) and abnormal composition of gut microbiota in patients with anxiety or depression. We appreciate these findings and would like to discuss the role of enterochromaffin cells (ECs) in brain function in this context.

Accumulating evidence has shown that neuropsychiatric diseases are frequently associated with gut microbiota disorders.2 It has been widely recognised that toxins within the human body mainly stem from the gut.3 The opening of intercellular tight junctions in the gut allow many toxins into the bloodstream that then have a deleterious effect on the brain, finally resulting in a series of neuropsychiatric symptoms. …