| [ Summary ] |
In the late 19th century, scientists believed that certain toxins generated in the gut could trigger depression, anxiety, and psychiatric diseases in a process known as 'autointoxication.' When a living body is exposed to harmful stressor(s), it activates the hypothalamic‒pituitary‒adrenal (HPA) axis and the sympathetic system in order to maintain its homeostasis. In 2004, Japanese scientists made the important observation that the HPA axis was activated in germ‒free mice and this hyperactivation was normalized after transplantation of normal gut microbiota. This discovery attracted attention to the 'brain‒gut‒gut microbiota axis'. Subsequent studies have shed more light on the relationship between gut microbiota and psychiatric illness. In particular, the clinical correlation between gut microbiota and depression/autism has been extensively investigated. It has been reported that patients with depression/autism have higher rates of various gastrointestinal symptoms. Studies on psychiatric disease and gut microbiota should be a priority in 'brain‒gut‒gut microbiota axis' research. |