Gut Brain Evidence

Evidence map

Gut brain axis: what the evidence base looks like

17 publications, 2 of them trials and 10 syntheses. This page describes the shape of that literature rather than summarising its conclusions.

Updated 3 min read 17 citations

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What the evidence on gut brain axis is made of Of 17 publications on this topic, the breakdown by study type: 10 meta-analysis, 2 randomised trial, 5 review. 1025meta-analysis (10)randomised trial (2)review (5)
17 publications, by study type. Volume is not strength — the same count can be a settled question or a pile of commentary, and which one it is depends almost entirely on this breakdown. Harvested from PubMed and Crossref; publication type as recorded by the source.

What this literature is made of

The synthesis is ahead of the primary literature here — reviews and meta-analyses drawing on a modest number of underlying studies. Treat confident conclusions with the caution the sample size deserves.

The distinction that matters most is between synthesis and primary research. A meta-analysis pools trials and is the closest thing to a settled answer a field produces. A narrative review is one group's reading of the same material and can be selective without being dishonest. Counting them together, which most citation counts do, obscures exactly the thing you want to know.

When the gut brain axis literature was published Publication years for the 17 papers on this topic, grouped into bands from before 2015 through to 2023 onwards. 2023 onwards9 papers2020-20227 papers2015-20191 papers
Still active. The most recent paper here is from 2025, so this is a field where an answer written today may not hold for long. Publication years as recorded by PubMed and Crossref.

How this page is built

Everything above is computed from the citations this site harvested from PubMed and Crossref, not written by hand. When the weekly harvest finds a new paper on this topic, these counts change and the characterisation changes with them. That is the point: a hand-written claim about how strong an evidence base is starts decaying the day it is written.

Publication type is taken as the source records it. That is imperfect — journals label inconsistently, and a paper indexed as a "review" may be a systematic one — so treat the bands as approximate. They are accurate enough to distinguish a trial literature from a commentary literature, which is the distinction that matters.

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Sauerkraut is preserved by lactic acid bacteria converting the cabbage's own sugars. Eugene Zelenko · CC BY-SA 4.0 · Wikimedia Commons

The strongest work on this topic

Ordered by study design first, then recency. The full set is listed in the references below.

  1. Gut microbiota variations in depression and anxiety: a systematic review — Cao Y, Cheng Y, Pan W et al., 2025, systematic review
  2. The complex relationship between gut microbiota and Alzheimer's disease: A systematic review — Zhou XP, Sun LB, Liu WH et al., 2025, systematic review
  3. Exploring the gut-exercise link: A systematic review of gastrointestinal disorders in physical activity — Al-Beltagi M, Saeed NK, Bediwy AS et al., 2025, systematic review
  4. The Microbiota-Gut-Brain Axis in Metabolic Syndrome and Sleep Disorders: A Systematic Review — Dos Santos A, Galiè S, 2024, systematic review
  5. Systematic review: Autism spectrum disorder and the gut microbiota — Korteniemi J, Karlsson L, Aatsinki A, 2023, systematic review
  6. Microbiota in Autism Spectrum Disorder: A Systematic Review — Lewandowska-Pietruszka Z, Figlerowicz M, Mazur-Melewska K, 2023, systematic review
  7. The gut microbiota-brain axis, psychobiotics and its influence on brain and behaviour: A systematic review — Barrio C, Arias-Sánchez S, Martín-Monzón I, 2022, systematic review
  8. The Gut Microbiome in Depression and Potential Benefit of Prebiotics, Probiotics and Synbiotics: A Systematic Review of Clinical Trials and Observational Studies — Alli SR, Gorbovskaya I, Liu JCW et al., 2022, systematic review
  9. The gut microbiota in anxiety and depression - A systematic review — Simpson CA, Diaz-Arteche C, Eliby D et al., 2021, systematic review
  10. Probiotics for Alzheimer's Disease: A Systematic Review — Naomi R, Embong H, Othman F et al., 2021, systematic review
How much research is there on gut brain axis?
17 publications are indexed here, of which 2 are trials and 10 are syntheses.
Does more research mean a stronger conclusion?
No. Composition matters more than volume — five randomised trials support a claim far better than fifty commentaries, and citation counts do not distinguish between them.
How current is this?
The most recent paper indexed here is from 2025. The set is refreshed weekly from PubMed and Crossref.
Why does this page not tell me the answer?
Because summarising a literature into a conclusion requires reading it, and doing that automatically is how confident nonsense gets published. This page tells you how much weight a conclusion could bear; the articles on this site do the interpreting.

References

Every citation below links to the original peer-reviewed record on PubMed or via DOI. Nothing here is a substitute for medical advice.

  1. The complex relationship between gut microbiota and Alzheimer's disease: A systematic review Zhou XP, Sun LB, Liu WH, et al. · Ageing research reviews · 2025 · Systematic review DOIPubMed 39662839
  2. Gut microbiota variations in depression and anxiety: a systematic review Cao Y, Cheng Y, Pan W, et al. · BMC psychiatry · 2025 · Systematic review DOIPubMed 40312666Full text
  3. Exploring the gut-exercise link: A systematic review of gastrointestinal disorders in physical activity Al-Beltagi M, Saeed NK, Bediwy AS, et al. · World journal of gastroenterology · 2025 · Systematic review DOIPubMed 40539198Full text
  4. The Microbiota-Gut-Brain Axis in Metabolic Syndrome and Sleep Disorders: A Systematic Review Dos Santos A, Galiè S · Nutrients · 2024 · Systematic review DOIPubMed 38337675Full text
  5. Systematic review: Autism spectrum disorder and the gut microbiota Korteniemi J, Karlsson L, Aatsinki A · Acta psychiatrica Scandinavica · 2023 · Systematic review DOIPubMed 37395517
  6. Microbiota in Autism Spectrum Disorder: A Systematic Review Lewandowska-Pietruszka Z, Figlerowicz M, Mazur-Melewska K · International journal of molecular sciences · 2023 · Systematic review DOIPubMed 38068995Full text
  7. The gut microbiota-brain axis, psychobiotics and its influence on brain and behaviour: A systematic review Barrio C, Arias-Sánchez S, Martín-Monzón I · Psychoneuroendocrinology · 2022 · Systematic review DOIPubMed 34942539
  8. The Gut Microbiome in Depression and Potential Benefit of Prebiotics, Probiotics and Synbiotics: A Systematic Review of Clinical Trials and Observational Studies Alli SR, Gorbovskaya I, Liu JCW, et al. · International journal of molecular sciences · 2022 · Systematic review DOIPubMed 35562885Full text
  9. The gut microbiota in anxiety and depression - A systematic review Simpson CA, Diaz-Arteche C, Eliby D, et al. · Clinical psychology review · 2021 · Systematic review DOIPubMed 33271426
  10. Probiotics for Alzheimer's Disease: A Systematic Review Naomi R, Embong H, Othman F, et al. · Nutrients · 2021 · Systematic review DOIPubMed 35010895Full text
  11. Mediterranean diet, gut microbiota, and cognitive decline in older adults with obesity/overweight and metabolic syndrome: a prospective cohort study Ni J, Hernández-Cacho A, Nishi SK, et al. · BMC medicine · 2025 · Randomised controlled trial DOIPubMed 41327300Full text
  12. Probiotic Supplementation Improves Cognitive Function and Mood with Changes in Gut Microbiota in Community-Dwelling Older Adults: A Randomized, Double-Blind, Placebo-Controlled, Multicenter Trial Kim CS, Cha L, Sim M, et al. · The journals of gerontology. Series A, Biological sciences and medical sciences · 2021 · Randomised controlled trial DOIPubMed 32300799Full text
  13. The gut microbiota-immune-brain axis: Therapeutic implications O'Riordan KJ, Moloney GM, Keane L, et al. · Cell reports. Medicine · 2025 · Review DOIPubMed 40054458Full text
  14. The microbiota-gut-brain axis and neurodevelopmental disorders Wang Q, Yang Q, Liu X · Protein & cell · 2023 · Review DOIPubMed 37166201Full text
  15. The Microbiota-Gut-Brain Axis in Psychiatric Disorders Góralczyk-Bińkowska A, Szmajda-Krygier D, Kozłowska E · International journal of molecular sciences · 2022 · Review DOIPubMed 36232548Full text
  16. Human gut microbiota/microbiome in health and diseases: a review Gomaa EZ · Antonie van Leeuwenhoek · 2020 · Review DOIPubMed 33136284
  17. The Microbiota-Gut-Brain Axis Cryan JF, O'Riordan KJ, Cowan CSM, et al. · Physiological reviews · 2019 · Review DOIPubMed 31460832