As we have learned from previous articles on our blog, bacteria play a significant role not only in digestion but also in the formation of our immune system. But there is more! Increasingly, research indicates a close connection between the development of the brain in early life and the process of colonization of the digestive system by microbes.

Many studies show that when you are born by caesarean section, bacteria that support the development of immunity do not colonize your body as they should. As it also turned out, numerous experiments on animal models have repeatedly shown the existence of an increased risk of mental disorders in individuals who were born in this way. Following this, a team of scientists from the University of Copenhagen set out to investigate whether the bacteria in the microbiota of the digestive system could moderate behavioural changes.

The course of the study

The first aim of the experiment was to verify whether the mice born via caesarean section have a disturbed development of the microbiota compared to individuals born naturally. If this part of the hypothesis was confirmed, the second stage of the study was to check whether the changes in the composition of bacteria affect the disturbances of the brain development process at an early stage, and, consequently, the psychophysical development of mice.

The animals were therefore divided into two groups. In group 1, the young were born without surgical intervention, while the individuals in group 2 were born after a cesarean section. In addition, it was made sure that all incidental factors that could affect the result of the experiment were excluded.

The way of birth affects the development of the microbiome and the mental sphere

The confirmation of the first part of the assumptions of Danish researchers was not a big surprise for them. As a result of birth by caesarean section, the microbiota of these mice was not appropriately colonized by the microorganisms. Researchers noticed a distinctly different bacterial composition than in mice that were born naturally. The experiment was repeated many times, but each time the results were very similar.

The researchers’ curiosity, however, was aroused by subsequent behavioural tests that were carried out on the test animals. Their results showed that mice born as a result of caesarean section were much more predisposed to anxiety. In addition, individuals from group 2 were much less interested in intercourse with other mice than those that were born into the world by the forces of nature. Their motor activity was also reduced.

How to measure stress levels in mice?

When a rodent finds itself in a situation that threatens its sense of security, it immediately empties its intestines. It is a natural mechanism whose task is to ease the escape of an animal from a potential threat, e.g. a predator. Thus, the more frequent defecation, the more stressed the animal is. This is how you can measure how high the level of anxiety is in a particular individual.

Studies on the relationship between the digestive system and the brain confirm that many mental disorders, such as depression and anxiety, can be mediated by an inappropriate composition of intestinal bacteria – especially in the early stages of the body’s development. The knowledge gained in this area creates an opportunity to develop new, effective options in the treatment of mental disorders, without the need to use pharmacological therapy, and through – less invasive – appropriate adjustment of the diet.

https://www.sciencedirect.com/science/article/pii/S0031938420305990