Several studies have established the correlation between gut microbiota and neurological disorders including blood brain barrier integrity [127], neurogenesis [128], maturation, and ramification of microglia [129], myelination [130], expression of neurotrophins like BDNF, oxytocin, and vasopressin [131], and release of neurotransmitters [132]. The gene discussed is BDNF; the disease is nervous system disorder.