Early life temperament predicts personality and risk of psychiatric and behavioral disorders later in life. Variation in temperament is influenced by biological and environmental factors. Research implicates a connection between the gut microbiome and physical as well as mental health conditions, creating a biological mechanism of interest. The gut microbiota is associated with brain regions that are linked to neurodevelopment and control of behavior. The aim of this study is to gather and analyze scientific evidence of associations between gut microbiota (GM) composition and diversity, and temperament in infancy and early childhood.
This study is a systematic review based on a literature search of the PubMed database. A total of 25 studies were identified, of which seven were included in the review following application of eligibility criteria.
The findings suggest an association between higher Surgency/Extraversion and a specific gut microbiota structure (beta diversity). Evidence supporting a link between GM alpha diversity and temperament was limited and warrants further research. On the taxonomic level, some interesting patterns emerged. Results implicate that an abundance of Bifidobacteriaceae may promote Surgency/Extraversion as well as Effortful Control/Regulation in the first year of life. Additionally, the families of Lachnospiraceae, Ruminococcaceae and Dialister of the phylum Bacillota, were found to influence Surgency/Extraversion and Negative Affectivity implicating a gut-brain connection mediated by their shared ability to produce butyrate, a short-chain fatty acid with known health benefits. Although these observations find support in literature, they remain tentative owing to the limited number of studies as well as the observed significant heterogeneity in methodology and study populations. Further research is needed to replicate results across different populations and timelines as well as to expand the scope of research to include functional aspects of the GM
