It can modulate the release and efficacy of monoaminergic transmission, alter of the activity and function of the hypothalamus-pituitary-adrenal axis, activate inflammation and immune response, as well as regulate the abundance of brain-derived neurotrophic factor (BDNF).8 In IBD, the gut-microbiota-brain axis seems linked to the development of a mental disorder due to the underlying inflammatory activity. Here, BDNF is linked to irritable bowel syndrome.