MicroorganismsJun 26, 2026

Gut bacteria types and variety in attention-deficit/hyperactivity disorder: A systematic review

Gut-Brain Axis Weekly Brief ↗PubMed ↗DOI ↗OA ↗

Updated Jun 27, 2026

Abstract

A total of 23 studies were included in the systematic review examining gut microbiota in individuals with ADHD.

Most studies found no significant differences in microbial diversity (alpha-diversity) between ADHD and control groups.
Beta-diversity analysis revealed significant differences in microbial composition between ADHD and control groups.
ADHD is often associated with a reduction in butyrate-producing bacteria and an increase in other specific taxa.
Some longitudinal studies indicated that early-life microbial patterns may precede an ADHD diagnosis.
Alterations in gut microbiota related to ADHD include changes in bacteria involved in short-chain fatty acid production and immune regulation.
Inconsistencies in findings may stem from methodological differences and potential confounding factors.

Simplified

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental condition. Growing evidence suggests that the gut-brain axis may contribute to its pathophysiology. However, findings regarding gut microbiota alterations in ADHD remain inconsistent. This systematic review aimed to synthesize the current evidence on the gut microbiota composition and microbial diversity in individuals with ADHD. A systematic search of PubMed, Scopus, and Web of Science was conducted up to 31 December 2025 following PRISMA guidelines, yielding 562 studies. Twenty-three studies published between 2015 and 2025 were included. Most studies reported no significant differences in alpha-diversity in ADHD and control groups. More consistently, beta-diversity analysis reported significant differences in microbial composition between ADHD and control groups. ADHD was often associated with a reduced abundance of Alistipes and butyrate producers such as Faecalibacterium and increased abundance of Roseburia and Agathobacter. Some longitudinal studies suggested that distinct early-life microbial patterns may precede the ADHD diagnosis. ADHD appears to be associated with alterations in the gut microbiota, particularly in taxa involved in short-chain fatty acid production and immune regulation. However, findings remain inconsistent due to methodological heterogeneity and potential confounding factors. Future research should prioritize longitudinal multi-omics approaches to clarify causal mechanisms and refine microbiota-targeted interventions.

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The authors declare no conflicts of interest.

PubMed

Gut bacteria types and variety in attention-deficit/hyperactivity disorder: A systematic review

Abstract

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Abstract

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Funding

Competing interests

Related papers

You found one interesting study. We’ll send the next 7.

What Lands in Your Inbox Each Week:

Recent issues from the gut-brain axis brief