LAUSR

Supplemental digital content is available in the text. ABSTRACT Objective Emerging evidence points toward a connection between mental health and the gut microbiota and its metabolites (e.g., short-chain fatty acids). It is unknown whether the gut microbiota is associated with the development of mental health problems (e.g., internalizing or externalizing behaviors) in preschool children. The objective of this study was to evaluate associations between the gut microbiota and internalizing and externalizing behaviors in preschool-aged children. Methods A community sample of 248 typically developing children (3–5 years of age) provided a stool sample for gut microbiota and SCFA analysis. Parents reported child internalizing and externalizing behaviors using the Child Behavior Checklist. Associations between child behaviors and gut microbiota measures were analyzed using Spearman correlations followed by an adjustment for multiple testing, with subanalysis conducted in children clinically “at risk” for behavioral problems compared with those who were not. Results There was a correlation between Shannon alpha diversity with internalizing behaviors (rs = −0.134, p = .035) and its subscale somatic complaints (rs = −0.144, p = .023). In addition, children clinically “at risk” for internalizing problems had decreased alpha diversity (U = 551, p = .017). Internalizing behaviors correlated with valerate and isobutyrate (rs = −0.147, p = .021; rs = −0.140, p = .028, respectively). Furthermore the somatic complaints subscale additionally correlated with acetate and butyrate (rs = −0.219, p = .001; rs = −0.241, p < .001, respectively). These findings were also present in children “at risk” for internalizing problems (U = 569, p = .026; U = 571, p = .028) and somatic complaints (U = 164, p = .004; U = 145, p = .001). Conclusions These analyses reveal novel associations between internalizing behaviors and the gut microbiota in preschool children. Furthermore, a relationship between somatic complaints and acetate and butyrate was identified, indicating that interventions that increase SCFA production warrant future investigation.