Another possible mechanism of microbiota for reducing anxiety is through the hypothalamic-pituitary-adrenal (H.P.A.)axis by enhancing hippocampal neurotrophic factor messenger expression R.N.A., which could decrease anxiety-like activity [43], which was demonstrated in a study that revealed improvements in subjects with stress-related disorders associated with HPA axis dysfunction, such as having a large proportion of glucocorticoid receptors and lower learning ability [44]. The gene discussed is NR3C1; the disease is stress-related disorder.