Bacteria in the Gut and Babies’ Fear

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Bacteria in the Gut and Babies’ Fear

Jim Windell

            All babes react to scary situations. Some overreact to danger – like a new person getting too close to them. Others may fail to react at all when, say, they come face to face with a barking dog.

           Is this because of their inborn temperament? Or is it something else entirely?

           New research suggests that the answer to this question may come – not from temperament or personality – but from a very surprising place – an infant’s digestive system.

           According to a new research study reported in the journal Nature Communications, research from Michigan State University and the University of North Carolina, Chapel Hill, looked at the vast community of microorganisms known as the gut microbiome – present in the human digestive system.

           To determine whether the gut microbiome was connected to fear response in humans, MSU's Rebecca Knickmeyer, an associate professor in the College of Human Medicine's Department of Pediatrics and Human Development, and her colleagues designed a pilot study with about 30 infants. They carefully selected a cohort to keep as many factors impacting the gut microbiome as consistent as possible. For example, all of the children were breast fed and none were on antibiotics.

           The researchers then studied each child’s microbiome by analyzing stool samples and they also assessed each child's fear response using a simple test: observing how a child reacted to someone entering the room while wearing a Halloween mask.

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

           Compiling all the data, the researchers saw significant associations between specific features of the gut microbiome and the strength of infant fear responses. For example, children with uneven microbiomes at one month of age were more fearful at one year of age. Uneven microbiomes are dominated by a small set of bacteria, whereas even microbiomes are more balanced. The researchers also discovered that the content of the microbial community at one year of age related to fear responses. Compared with less fearful children, infants with heightened responses had more of some types of bacteria and less of others.

           As part of the study, the team also imaged the children's brains using MRI technology. They found that the content of the microbial community at one year was associated with the size of the amygdala – a part of the brain involved in making quick decisions about potential threats.

           That may mean, according to this research, that the microbiome may influence how the amygdala develops and operates. That is only one of several interesting possibilities uncovered by this new study, which Knickmeyer and her the team are currently working to replicate.

           Studies of the connection between microbiomes and fear responses in animals led Knickmeyer and her team to look for something similar in humans. Studying how humans, especially young children, handle fear is important because it can help forecast mental health in some cases.

           "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" said Knickmeyer, who also works in MSU's Institute for Quantitative Health Science and Engineering. "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."

           To read the original journal article, find it with this reference:

Alexander L. Carlson, Kai Xia, M. Andrea Azcarate-Peril, Samuel P. Rosin, Jason P. Fine, Wancen Mu, Jared B. Zopp, Mary C. Kimmel, Martin A. Styner, Amanda L. Thompson, Cathi B. Propper, Rebecca C. Knickmeyer. Infant gut microbiome composition is associated with non-social fear behavior in a pilot study. Nature Communications, 2021; 12 (1) DOI: 10.1038/s41467-021-23281-y







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