Kennedy, Gwen, Spence, Vance A, McLaren, Margaret et al. · Free radical biology & medicine · 2005 · DOI
This study measured harmful molecules called free radicals in the blood of ME/CFS patients and compared them to healthy people. Researchers found that ME/CFS patients had higher levels of these damaging molecules, and in patients without heart disease risk factors, the amount of free radicals correlated with how severe their symptoms were, particularly fatigue after exertion and joint pain.
This was the first study to demonstrate elevated isoprostanes—a gold-standard marker of oxidative damage—in ME/CFS patients and link them to clinical symptom severity. Identifying a potential biochemical mechanism underlying ME/CFS could inform future therapeutic strategies targeting oxidative stress and validate patient-reported symptoms with objective biomarkers.
This study does not prove that oxidative stress causes ME/CFS symptoms, only that they are associated. The cross-sectional design cannot establish directionality; elevated oxidative stress could be a consequence of ME/CFS rather than a cause. The finding that oxidative stress correlated with symptoms only in the low-risk cardiovascular group requires replication and may reflect confounding or subgroup-specific mechanisms.
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
Kennedy, Gwen, Spence, Vance A, McLaren, Margaret, Hill, Alexander, Underwood, Christine, & Belch, Jill J F (2005). Oxidative stress levels are raised in chronic fatigue syndrome and are associated with clinical symptoms.. Free radical biology & medicine. https://doi.org/10.1016/j.freeradbiomed.2005.04.020
BibTeX
@article{mecfsatlas-kennedy-2005-oxidative-stress,
author = {Kennedy, Gwen and Spence, Vance A and McLaren, Margaret and Hill, Alexander and Underwood, Christine and Belch, Jill J F},
title = {Oxidative stress levels are raised in chronic fatigue syndrome and are associated with clinical symptoms.},
journal = {Free radical biology & medicine},
year = {2005},
doi = {10.1016/j.freeradbiomed.2005.04.020},
note = {PubMed: 16085177},
url = {https://www.mecfsatlas.com/evidence/kennedy-2005-oxidative-stress},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/kennedy-2005-oxidative-stress
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