What can the gut microbiome teach us about the connections between child physical and mental health? A systematic review.

A deeper understanding of the gut-brain axis is of significance in pediatrics, given the influential role of early childhood experiences and exposures in shaping the microbiome, and health, across the life course. This systematic review synthesized evidence on the connection between the gut microbiome and mental health in children with physical illness. Six electronic databases were systematically searched and data extracted according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Of 1,476 identified articles, 11 articles reporting on nine unique studies (all randomized controlled trials) were included. Most studies examined the gut microbiome in infants with colic, while the remaining studies investigated outcomes in children aged 1 day to 18 years at risk for atopic dermatitis or irritable bowel syndrome. Baseline and postintervention gut microbiome differences varied across studies. Findings on psychological functioning also varied, with only half of the captured studies showing a positive effect of intervention on psychological well-being. Only two studies analyzed the association between the gut microbiome and psychological outcomes, each with a different pattern of results. As the field moves forward, it will be critical to gain a better understanding of the microbiome characteristics that influence mental health outcomes in pediatric populations.