Study Examines Microbiome Content for 1-Month and 1-Year Old Infants
The microbiome is the collection of trillions of microorganisms that colonize the digestive tract. Each person has a completely unique microbiome, made up of a network of microbiota originally determined by their DNA. The microbiome develops rapidly during the first year of life. Previous research has linked human behaviors, including fear and anxiety, to the composition of the microbiome. It was due to these reasons that a research team from Michigan State University set out to study the emergence of fear responses in infants around 12-months old and examine if fear behavior is influenced by the development and composition of the microbiome. The Michigan State researchers theorized that there are critical windows in the development of the brain and nervous system in which variations in microbiome composition could impact infants’ fear behaviors and perhaps influence the physical structure of brain areas involved in generating fear. By recruiting a group of 34 infants, the study’s authors assessed microbiome contents and the volume of key brain regions at ages 1-month and 12-months. At the second assessment point, they also examined social and non-social types of fear behaviors in the infants. The study’s results indicated that the composition of the microbiome at 1-year “is significantly associated with increased fear behavior” and that differences in microbial colonization causes differences in fear. The researchers based these findings on a task designed to measure non-social fear. They also discovered that certain qualities of the 1-month microbiome were additionally associated with increased non-social fear at 1-year. Additionally, this study demonstrated a “suggestive” relation between contents of the infant microbiome and volumes of the amygdala and the prefrontal cortex. Despite finding associations between microbiome and variations between individual fear responses among the infants, the study’s authors say it is too early to label any specific microbiome contents as good or bad. This is mostly due to differences among individuals and also because some microbes may have positive and negative impacts in different contexts.
