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Redox imbalance links COVID-19 and myalgic encephalomyelitis/chronic fatigue syndrome.

Paul, Bindu D, Lemle, Marian D, Komaroff, Anthony L et al. · Proceedings of the National Academy of Sciences of the United States of America · 2021 · DOI

Quick Summary

This review examines how COVID-19 and ME/CFS may share similar biological problems, particularly an imbalance in how the body handles harmful molecules called free radicals. Both conditions appear to involve problems with inflammation, energy production in cells, and a slowed metabolism. While this research shows these biological abnormalities exist in both illnesses, more studies are needed to understand exactly how they work together and how to treat them.

Why It Matters

This review provides scientific validation that ME/CFS and long COVID-19 involve measurable biological abnormalities rather than being purely psychological conditions. Understanding these shared mechanisms could accelerate development of treatments applicable to both illnesses and help clinicians recognize long COVID-19 as potentially part of the ME/CFS disease spectrum.

Observed Findings

  • People with acute COVID-19 and ME/CFS show measurable redox imbalance (altered oxidative stress markers)
  • Both conditions demonstrate systemic and neuroinflammation with abnormal cytokine patterns
  • Cells in both conditions show impaired ability to produce sufficient ATP (energy currency)
  • Both illnesses are associated with a hypometabolic state (slowed overall metabolic rate)
  • These biological abnormalities also appear in other neurological diseases, suggesting shared pathophysiological mechanisms

Inferred Conclusions

  • Redox imbalance, inflammation, energy metabolism deficits, and hypometabolism are interconnected phenomena in ME/CFS and acute COVID-19 that may drive symptom severity
  • Long COVID-19 shares phenotypic features with ME/CFS and may involve overlapping molecular pathology requiring similar investigation
  • Identifying these molecular mechanisms provides targets for developing novel therapeutics for both post-infectious conditions
  • The bidirectional relationships among these biological abnormalities suggest treating one pathway may have cascading effects on others

Remaining Questions

  • Do these same biological abnormalities characterize long COVID-19 patients, and to what degree?
  • Which of these mechanisms is primary (causative) versus secondary (compensatory), and what triggers their initial development?
  • Why do some infected individuals develop persistent post-viral symptoms while others recover completely?
  • Which therapeutic interventions targeting redox balance, inflammation, or metabolism show promise in clinical trials for ME/CFS or long COVID-19?

What This Study Does Not Prove

This review does not prove that redox imbalance directly causes ME/CFS or long COVID-19—it documents associations that may be correlational. It also does not establish that all ME/CFS cases involve identical biological mechanisms, nor does it provide evidence that current treatments targeting these pathways will be effective in patients.

Topics

NeuroinflammationPost-Exertional Malaise

Tags

Symptom:Post-Exertional MalaiseCognitive DysfunctionUnrefreshing SleepOrthostatic IntoleranceFatigue
Biomarker:CytokinesMetabolomicsBlood Biomarker
Phenotype:Infection-TriggeredLong COVID Overlap
Method Flag:Exploratory Only

Metadata

DOI
10.1073/pnas.2024358118
PMID
34400495
Review status
Machine draft
Evidence level
Established evidence from major reviews, guidelines, or evidence maps
Last updated
7 April 2026