Gut bacteria influences how babies experience the feeling of fear

EAST LANSING, Mich. — The body’s gut flora influences many other organs and areas outside of the intestines. A good balance of healthy gut bacteria improves mood, decreases weight, and according to recent studies, benefits the development of the brain. Interestingly, new research shows that a healthier gut decreases the feeling of fear in infants.

A team of researchers from Michigan State University and the University of North Carolina at Chapel Hill set out to study the connection between brain formation and the type of bacteria in a baby’s gut. This association would also shed light on the reason why some babies scare easier than others.

The microbiome consists of thousands of bacterial strains that function to break down food. According to the team, babies that responded to fear in a more powerful way possess different strains of gut bacteria than those who responded more moderately. Since brain function is linked to bacteria in the gut, these reactions to fear can signal neurological issues.

“This early developmental period is a time of tremendous opportunity for promoting healthy brain development,” said Rebecca Knickmeyer, the study’s leader from MSU, in a statement. “The microbiome is an exciting new target that can be potentially used for that.”

Previous research shows that certain types of gut bacteria in animals with the way they respond in scary situations. This prompted Knickmeyer, an associate professor of Pediatrics and Human Development at MSU’s College of Human Medicine, and her colleagues to look for comparable results in humans, particularly children. In certain circumstances, understanding how individuals deal with fear might assist the prediction of future mental health issues.

For example, young children who over-respond to fear could be prone to anxiety or other neurological disorders. Conversely, those that show little to no response to scary situations could grow to lack certain crucial social characteristics that allow them to be healthy, civilized young people. “Fear reactions are a normal part of child development. Children should be aware of threats in their environment and be ready to respond to them” says Knickmeyer. “But if they can’t dampen that response when they’re safe, they may be at heightened risk to develop anxiety and depression later on in life.”

For this particular study, the team strategically chose 30 infants with similar backgrounds to prevent outside components from affecting the results. One of the corresponding factors was the fact that all babies chosen had been fed breastmilk, and all had not been subject to antibiotics.

To determine the types of bacteria in each child’s gut, the team evaluated samples of fecal matter from each individual. The team tested each child’s reaction to fear by evaluating the way they responded to an individual wearing a scary Halloween outfit.

“We really wanted the experience to be enjoyable for both the kids and their parents. The parents were there the whole time and they could jump in whenever they wanted,” says Knickmeyer. “These are really the kinds of experiences infants would have in their everyday lives.”

Results show substantial links between particular aspects of microbiota in the gut and the severity of baby anxiety reactions. Children with unbalanced gut bacteria (not having as many good bacterial strains) at one-month-old were more apprehensive at age one. Additionally, the composition of the gut flora during the first year was similarly linked to fear reactions. Certain types of bacteria overpopulated in those who exhibited exaggerated responses to fear, while different bacterial strains dominated in those with more moderate reactions.

The researchers scanned each child’s brain via MRI and discovered that the diameter of the amygdala, the region of the inner cortex necessary to make immediate choices about possible dangers, was linked to the composition of the microflora. This indicates that the amygdala’s formation and activity may be regulated by the bacteria in the gut.

Knickmeyer, also a scientist at the Institute for Quantitative Health Science and Engineering at MSU, is ready to begin new research to further investigate this association. She and her team hope to answer questions about brain development and possible brain disorders with additional research centered around gut microbiomes. “We have a great opportunity to support neurological health early on,” she said. “Our long-term goal is that we’ll learn what we can do to foster healthy growth and development.”

The study is published in the journal Nature Communications.