The Gut-Brain Connection

A new research review suggests better understanding the gastrointestinal microbiome may help psychiatrists treat mental health disorders such as depression.

“There is strong communication between the gastrointestinal tract and the brain,” says Juan M. Lima-Ojeda, a physician and researcher at the University of Regensburg. This finding comes after Ojeda and his team completed a review of over 120 peer-reviewed articles on the microbiome-gut-brain axis. They published their review in Frontiers of Psychiatry, then made their findings most easily digestible for Frontiers for Young Minds.

The microbiota-gut-brain (MGB) axis is a direct connection between gut bacteria and the brain. The MGB axis is a neuroendocrine-immune system, meaning it links the nervous system, the endocrine system, and the immune system. The gastrointestinal tract is connected to the brain through an important nerve called vagus nerve, which acts like a main phone line. This communication goes in both directions and also includes the hypothalamic-pituitary-adrenal (HPA) axis, a system that includes the hypothalamus, pituitary and adrenal glands. The HPA axis links the nervous system to the endocrine system and controls the response of our bodies to stress.

Because of the interconnectedness of the MGB and HPA axes, long-term stress can damage the bacteria living in the gut. A difficult life situation can be enough to reduce the diversity of gut bacteria and to increase the numbers of bad bacteria in the gut. These changes in the gut microbiota can cause changes in the brain as well—increasing the risk of brain disorders such as depression.

At present, the exact mechanism that produces depression is unknown. It is possible that the changes in the body that result in depression involve the participation of the three systems that make up the MGB axis: the nervous, endocrine, and immune systems. Therefore, it is hypothesized that emotional stress, malnutrition and high use of specific antibiotics may be risk factors that alter the MGB axis and increase the risk of developing depression.

In another study at the University of Regensburg, researchers tested the use of the antibiotic minocycline as a treatment for depression in preclinical and clinical designs. Minocycline fights bacteria in the body and is routinely used to combat UTIs, respiratory infections, skin infections and more. Three weeks of minocycline treatment in rats alleviated the depressive-like phenotype. These preclinical results further support the microbiome-gut-brain axis as potential target in the treatment of depression. The result of the clinical study (leading center Charité Berlin) will clarify soon whether depressed patients have beneficial antidepressant treatment effects.

According to the research, the best thing you can do to protect your gut and brain: eat a balanced diet.