Evidence of a connection between our gut microbiota, development, and behavior is mounting. A new study links behavioral issues and socioeconomic stress to a distinct microbiome.

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Are behavior and the microbiome related?

Children receive the first microbes that go on to colonize their gut during birth. Scientists have studied the importance of the many microbial species and identified key roles during infant development.

However, the field is only slowly emerging from infancy, and data on other age groups are sparse.

A new study looking at early school-age children highlights links between behavior, socioeconomic stress, and the gut microbiome. Parental behavior also has a big role to play, according to the researchers.

The senior study author is Thomas Sharpton, an associate professor in the Department of Microbiology at Oregon State University in Corvallis.

Working with collaborators from the University of Oregon and other institutions, the team’s results now feature in the journal mBio.

Sharpton and colleagues set out to determine if there are any links between the composition of a child’s microbiome and their socioeconomic risk, behavior dysregulation, and the behavior of their parent or caregiver.

“Most studies to date have linked microbiome composition to infant and toddler behaviors, such as extroversion, fear, and cognitive development,” he explains.

“It hasn’t been clear, though, that the microbiome associates with other forms of behavioral dysregulation or if it links to the onset of psychiatric disorders and problem behaviors.”

The team recruited 40 families with children aged 5–7 from a variety of socioeconomic groups. The caregivers filled in questionnaires about the children’s behavior and the quality of their relationship. They also provided a stool sample for the gut microbiome analysis.

The team found that children at higher socioeconomic risk had different microbial profiles to their peers at lower socioeconomic risk. However, the role of a child’s caregiver was key.

“These results provide evidence that, in terms of the microbiome’s functional potential, caregiver behavior can moderate the associations between socioeconomic risk covariates and the microbiome,” they explain in the paper.

When the researchers looked at behavioral dysregulation, they saw similar results.

Children with certain types of behavioral dysregulation, such as the ability to inhibit impulses and depression, had distinct microbial profiles. However, “caregiver behavior may moderate these associations.”

When the researchers dug deeper, they identified several bacterial species behind some of these interactions.

Specifically, they saw that Bacteroides fragilis was strongly linked with socioeconomic risk and behavioral dysregulation.

“Interestingly, B. fragilis [was] associated with reduced levels of aggression, anxiety, emotional reactivity, externalizing behavior, and impulsivity, as well as an increase in inhibitory control (i.e., better mental health),” the authors explain in the paper.

“Recent psychological research links chronic intestinal inflammation to depression and anxiety. In light of these observations, we hypothesize that the anti-inflammatory properties of Bacteroides may impact intestinal inflammation in children to subsequently influence behavior.”

B. fragilis was also associated with lower reported incidents of family turmoil,” they continue. “These results are noteworthy because studies in mice have found that B. fragilis modulates the immune system and protects against pathogen-induced inflammation, specifically through the production of polysaccharide A.”

The team saw that butyrate-producing bacterial species had both positive and negative effects.

“Our pairwise correlations identified three known butyrate-producing taxa — Coprococcus comes, Eubacterium rectale, and Roseburia inulinivorans — that associate with various aspects of socioeconomic risk or behavioral dysregulation,” they write.

“The production of butyrate from plant-derived polysaccharides by the gut microbiome is understood to be an important mechanism through which high fiber diets promote beneficial health effects.”

On the other hand, they also saw an association between C. comes and increased aggressive behavior, as well as between E. rectale and reduced inhibitory control.

Inflammation in the gut may be central to whether or not a child shows signs of behavioral dysregulation.

However, it is important to note the study’s limitations. This type of analysis does not allow researchers to establish cause and effect.

Also, because this study had a small number of participants, people should treat the results as preliminary. The researchers also point out that they didn’t measure the impact of the children’s diets in this study, which may be a significant confounding factor.

Still, the results are thought-provoking, and future studies are sure to uncover the strength of the relationships between a child’s microbiome, their caregiver, and their developmental trajectory.