Temperament in Early Childhood Is Associated With Gut Microbiota Composition and Diversity.

Temperament is a key predictor of human mental health and cognitive and emotional development. Although human fear behavior is reportedly associated with gut microbiome in infancy, infant gut microbiota changes dramatically during the first 5 years, when the diversity and composition of gut microbiome are established. This period is crucial for the development of the prefrontal cortex, which is involved in emotion regulation. Therefore, this study investigated the relationship between temperament and gut microbiota in 284 preschool children aged 3-4 years. Child temperament was assessed by maternal reports of the Children's Behavior Questionnaire. Gut microbiota (alpha/beta diversity and genera abundance) was evaluated using 16S rRNA sequencing of stool samples. A low abundance of anti-inflammatory bacteria (e.g., Faecalibacterium) and a high abundance of pro-inflammatory bacteria (e.g., Eggerthella, Flavonifractor) were associated with higher negative emotionality and stress response (i.e., negative affectivity, β = -0.17, p = 0.004) and lower positive emotionality and reward-seeking (i.e., surgency/extraversion, β = 0.15, p = 0.013). Additionally, gut microbiota diversity was associated with speed of response initiation (i.e., impulsivity, a specific aspect of surgency/extraversion, β = 0.16, p = 0.008). This study provides insight into the biological mechanisms of temperament and takes important steps toward identifying predictive markers of psychological/emotional risk.