Microbial communities are hypothesized to influence mental health states via the gut-brains axis. The gut, which also known as the “second brain” is linked through several nerves and neurons to the brain. Thus cytokine production in response to microbes, as well as precursors for neurotransmitter produced to microbes, can then travel to and influence the brain. An example of this, is a study in which depressed mice whose vagus nerve was severed (removing the link between the gut and the brain), the symptoms of depression were no longer alleviated with probiotic use.
The brain and mental health states have also been found to, in turn, influence gut health. This is through the gut-brain axis, once again, and neurotransmitters, hormones, and steroids produced by the brain can influence the gut. One example is how catecholamines and norepinephrine during stress can travel to the gut and cause dysbiosis; there is an overall decrease in motility and nutrient absorption.
Thus overall, these relationships can influence health and disease because there are never ending lists and ways to promote mental health, which can then promote gut health and limit the risks of diseases associated with gut dysbiosis. On the other side, taking care of gut health can encourage a healthy mental state. Thus they can both promote health and disease by influencing on another.
