Rao, A Venket, Bested, Alison C, Beaulne, Tracey M et al. · Gut pathogens · 2009 · DOI
This study tested whether a specific probiotic bacteria could help reduce anxiety in ME/CFS patients. Thirty-nine patients took either the probiotic or a placebo daily for two months. The researchers found that patients taking the probiotic had lower anxiety scores compared to those taking placebo, and their gut bacteria levels changed in expected ways.
Anxiety affects many ME/CFS patients and current treatment options are limited. This study provides preliminary evidence that modifying gut bacteria through probiotics may offer a non-pharmacological approach to reducing emotional symptoms, opening a new avenue for symptom management in ME/CFS.
This pilot study does not prove that probiotics are an effective treatment for ME/CFS—the small sample size and short duration limit generalizability. It also does not establish the causal mechanism by which the bacteria reduce anxiety, nor does it clarify whether the observed effect would persist beyond two months or which CFS patients might benefit most.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Rao, A Venket, Bested, Alison C, Beaulne, Tracey M, Katzman, Martin A, Iorio, Christina, Berardi, John M, et al. (2009). A randomized, double-blind, placebo-controlled pilot study of a probiotic in emotional symptoms of chronic fatigue syndrome.. Gut pathogens. https://doi.org/10.1186/1757-4749-1-6
BibTeX
@article{mecfsatlas-rao-2009-randomized-double,
author = {Rao, A Venket and Bested, Alison C and Beaulne, Tracey M and Katzman, Martin A and Iorio, Christina and Berardi, John M and Logan, Alan C},
title = {A randomized, double-blind, placebo-controlled pilot study of a probiotic in emotional symptoms of chronic fatigue syndrome.},
journal = {Gut pathogens},
year = {2009},
doi = {10.1186/1757-4749-1-6},
note = {PubMed: 19338686},
url = {https://www.mecfsatlas.com/evidence/rao-2009-randomized-double},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-27. https://www.mecfsatlas.com/evidence/rao-2009-randomized-double
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