The Gut Microbiome of Youth Who Have Behavioral and Mental Health Problems: A Scoping Review

Background: Mental health conditions have increased over the past several decades. While there is growing evidence that the gut microbiome affects mental health, there are limited studies focused on children, adolescents, and young adults. This scoping review examined the existing literature and compared findings on the relationships between the gut microbiome with mental health across these younger age groups. Methods: A literature search using PubMed, PsycINFO, and CINAHL was performed, and bibliographies were manually searched. Eighteen articles met eligibility for our scoping review. Findings from each study were evaluated, focusing on bacterial composition and diversity among children/adolescents and young adults. Results: There were no studies specifically on the adolescent age group, so data was synthesized comparing the child/adolescent (2 to <18 years of age) and young adult (18-25 years of age) groups. Studies utilized several different methods for gut microbiome analysis and examined various mental health conditions. Findings for both age groups were mostly inconsistent. However, Bifidobacteria seems to be associated with better mental health. Alpha diversity was lower for children/adolescents with ADHD and high stress but higher for young adults with ADHD and Major Depressive Disorder. Limitations: There were inconsistencies across studies, likely due to differences in mental health problems examined, populations assessed, and research designs or measurements used. Conclusions: Future research should replicate studies to confirm findings, examine lower taxonomic levels, consider longitudinal designs to assess for directionality, and consider clinical trials to examine the effects of probiotics with the same strains to manage mental health symptoms.