New insights into how the infant microbiome impacts early childhood behavior in boys and girls

A Dartmouth-led study, published in Pediatric Research, has shown a direct association between infant microbiome composition and early childhood behavioral health.
Studies in the past have shown a link between gut microbiome, which is the entire community of microbes living in the intestinal tract, and behavioral disorders like anxiety, depression, and attention deficit hyperactivity disorder (ADHD). However, human data has not been available to determine the role of the microbiome in infancy and their impact on outcomes for children. This is because there have not been enough data to compare the results between boys and girls.

"Most of the previous research has focused on participants who already have depressive or anxious symptoms," says Hannah Laue, ScD. She is a research associate at Dartmouth’s Geisel Medical School and the first author of this study. "We wanted to examine the early stages of these behaviors to determine if the microbiome is influencing neurobehaviors or the opposite."

Laue says that by focusing on infancy, the investigators were able to study a crucial window of time. This is when the microbiome (and the brain) are at their fastest development and may be most vulnerable to changes in microbiome.

The study team used the New Hampshire Birth Cohort Study to determine if differences in infant microbiome could be related to neurobehavior. It also examined whether the behavior was different in boys and in girls. This study was initiated in 2009 in order to examine the impact of environmental factors on the outcomes of pregnancy and birth. Dartmouth's Drs. The cohort includes a longitudinal monitoring of the microbiome at birth, starting at birth, to better understand how it affects the health and well being of children.

The researchers collected stool samples from 260 infants over a period of six weeks, one and two years. They were able to identify the microbes and their functions in each participant's intestines. The Behavioral Assessment System For Children was used to measure their behavioral development. It measures a variety of adaptive and clinical behaviors in children and young people.

Researchers were able to prove that microbiome changes are preceded by behavioral changes. The study team also discovered that microbiomes in infants and young children were linked to neurobehaviors like anxiety, depression, hyperactivity, social behavior, and other behaviors in a time-and sex-specific way.

Laue says, "For example, increased diversity in the gut was more beneficial for boys. It was associated with fewer disorders like anxiety and depression but not among girls." "We observed differences in social behavior with microbiomes at later stages. This was where we found evidence that diversity could be beneficial for both boys and girls." We also found that there were differences between certain bacteria species and their essential functions, such as vitamin B synthesis, which were directly related to these outcomes.

Although their findings didn't reveal a microbial species capable of preventing children from developing anxiety and depression, Laue says that future research could look at the specific findings to determine if they could be used as probiotics or any other type of intervention such as breastfeeding promotion.