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ME/CFS Atlas — A public knowledge atlas for ME/CFS

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ME/CFS Atlas is an evidence reference platform, not a medical provider. Content is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional.

© 2026 ME/CFS Atlas

ME/CFS Evidence Browser — Classified Studies on Myalgic Encephalomyelitis

Evidence browser

Search and filter 6,129 studies by evidence level, diagnostic criteria, PEM status, and research domain. Each entry links to the original source.

Studies sorted by evidence level, then year. Browse by topic instead →

Evidence level (E0–E3) reflects study type and replication, not methodological quality. A weak systematic review still sits at E0. How evidence levels work →

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260 studies

E0 — Consensus630E1 — Replicated320E2 — Moderate2,760E3 — Preliminary2,419

ME/CFS4,015Long COVID207Post-infectious189Overlapping1,034

Required for diagnosis410Not specified / unclear2,192Not required3,527

Post-Exertional Malaise1,040Cognitive Dysfunction1,713Pain1,607Unrefreshing Sleep786Orthostatic Intolerance470

Cytokines813Gene Expression566Metabolomics469Neuroimaging464Autoantibodies456

Infection-Triggered1,160Long COVID Overlap564Pediatric495Severe227

Strong Phenotyping427Sex-Stratified326Severe ME Included115

Systematic Review258Meta-Analysis59RCT300

Peer-reviewed6,072Preprint3Unclear54

241–260 of 260 studies

E3 PreliminaryReviewPEM not requiredReview-Narrative

Neural control of force output during maximal and submaximal exercise.

St Clair Gibson, A, Lambert, M L, Noakes, T D·Sports medicine (Auckland, N.Z.)·2001

This review challenges the common belief that muscle fatigue during exercise comes only from chemical changes in muscles themselves. Instead, the authors propose that the brain and nervous system actively control and limit how hard we can exercise to protect our bodies from damage. Interestingly, they note that people with ME/CFS experience fatigue even at rest, suggesting fatigue may be a protective signal from the nervous system rather than a simple muscle problem.

ME/CFS (general)

E3 PreliminaryMechanismPEM unclearMechanistic

Specific oxidative alterations in vastus lateralis muscle of patients with the diagnosis of chronic fatigue syndrome.

Fulle, S, Mecocci, P, Fanó, G et al.·Free radical biology & medicine·2000

Researchers examined muscle tissue from ME/CFS patients and found signs of oxidative damage—a type of cellular wear and tear similar to rust forming on metal. The patients' muscles showed damage to DNA and fats in cells, and their bodies had ramped up production of protective chemicals called antioxidants to fight back against this damage. This suggests ME/CFS may cause real, measurable changes in how muscle cells function at a chemical level.

ME/CFS (general)

E3 PreliminaryCohortPEM not requiredCross-Sectional

"I could not lift my arm holding the fork...". Living with chronic fatigue syndrome.

Söderlund, A, Skoge, A M, Malterud, K·Scandinavian journal of primary health care·2000

This study asked 12 people with ME/CFS to describe what living with the illness is really like. They reported extreme exhaustion that goes far beyond normal tiredness, along with muscle weakness, pain, memory problems, sleep issues, and heightened sensitivity to light, sound, and smells. These symptoms made everyday activities like cooking, talking, and housework unpredictably difficult, which disrupted their social lives and relationships.

ME/CFS (general)

E3 PreliminaryCohortPEM not requiredObservational

Acute effects of thirty minutes of light-intensity, intermittent exercise on patients with chronic fatigue syndrome.

Clapp, L L, Richardson, M T, Smith, J F et al.·Physical therapy·1999

This study looked at whether 30 minutes of light, on-and-off walking on a treadmill would make symptoms worse in people with ME/CFS. Ten participants did 10 short 3-minute walks with 3-minute rest breaks in between. The researchers found that this type of gentle, intermittent exercise did not worsen symptoms immediately or up to a week afterward.

ME/CFS (general)

E3 PreliminaryMechanismPEM not requiredMechanistic

Impaired oxygen delivery to muscle in chronic fatigue syndrome.

McCully, K K, Natelson, B H·Clinical science (London, England : 1979)·1999

This study found that muscles in people with ME/CFS are not receiving oxygen as quickly and efficiently as they should after exercise or when blood flow is temporarily stopped. The researchers measured how fast oxygen returns to calf muscles and found it took significantly longer in ME/CFS patients compared to healthy people. They also found that the muscles' ability to use oxygen for energy was reduced by about 20% in ME/CFS patients.

ME/CFS (general)

E3 PreliminaryCohortPEM unclearCase-Control

Managing chronic fatigue syndrome: overview and case study.

Jason, L A, Melrose, H, Lerman, A et al.·AAOHN journal : official journal of the American Association of Occupational Health Nurses·1999

This study explains 'envelope theory,' a practical approach where people with ME/CFS stay within their energy limits to avoid crashes and gradually build tolerance. By tracking energy levels over time, patients and doctors can better understand each person's unique patterns and what activities trigger setbacks.

ME/CFS (general)

E3 PreliminaryMechanismPEM unclearObservational

Demonstration of delayed recovery from fatiguing exercise in chronic fatigue syndrome.

Paul, L, Wood, L, Behan, W M et al.·European journal of neurology·1999

This study tested whether people with ME/CFS recover more slowly from exercise than healthy people. Researchers had both patients and control subjects perform intense leg muscle contractions, then measured how quickly their muscle strength returned to normal. The results confirmed that while both groups got tired similarly during exercise, people with ME/CFS took much longer to recover their muscle strength afterward—even 24 hours later.

ME/CFS (general)

E3 PreliminaryMechanismPEM not requiredCross-Sectional

Corticomotor excitability and perception of effort during sustained exercise in the chronic fatigue syndrome.

Sacco, P, Hope, P A, Thickbroom, G W et al.·Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology·1999

This study examined whether the fatigue and exercise difficulty in ME/CFS comes from the brain and nervous system rather than just muscle weakness. Researchers used magnetic stimulation to measure how the motor cortex (the brain region controlling movement) responds during sustained muscle contractions in ME/CFS patients and healthy controls. They found that people with ME/CFS had shorter exercise endurance, felt more exhausted during effort, and showed different patterns of brain-to-muscle signaling compared to healthy people.

ME/CFS (general)

E3 PreliminaryMechanismPEM not requiredMechanistic

Mouse running activity is lowered by Brucella abortus treatment: a potential model to study chronic fatigue.

Ottenweller, J E, Natelson, B H, Gause, W C et al.·Physiology & behavior·1998

Researchers infected mice with a killed bacterium to see if it would create a model similar to ME/CFS. The mice immediately stopped running and grooming after infection, then slowly recovered over 2-4 weeks—though some mice recovered faster than others. Interestingly, during recovery, the mice could only run for short periods at first before becoming exhausted, gradually building up their endurance over time.

ME/CFS (general)

E3 PreliminaryCohortPEM not requiredCase-Control

The case history of an elite ultra-endurance cyclist who developed chronic fatigue syndrome.

Rowbottom, D G, Keast, D, Green, S et al.·Medicine and science in sports and exercise·1998

Researchers studied an elite cyclist who developed ME/CFS and tested his fitness before, during, and after his illness. His oxygen capacity and exercise performance dropped significantly during illness, but surprisingly remained low even after he felt clinically better. The authors suggest these fitness losses were due to prolonged inactivity from being sick rather than damage to his muscles' ability to use oxygen.

ME/CFS (general)

E3 PreliminaryReviewPEM not requiredReview-Narrative

Chronic fatigue syndrome: a literature review from a physiatric perspective.

Jain, S S, DeLisa, J A·American journal of physical medicine & rehabilitation·1998

This review examined over 200 scientific studies about ME/CFS to understand what we know about the condition, particularly focusing on thinking problems and exercise. The authors found that while patients often report cognitive difficulties, actual measured problems are subtle and mainly affect how quickly the brain processes complex information. Brain imaging studies suggest changes may occur in the white matter of the brain rather than in the muscles themselves.

ME/CFS (general)

E3 PreliminaryMechanismPEM not requiredCross-Sectional

Decreased postexercise facilitation of motor evoked potentials in patients with chronic fatigue syndrome or depression.

Samii, A, Wassermann, E M, Ikoma, K et al.·Neurology·1996

This study measured how the brain's motor cortex responds to exercise using magnetic stimulation in people with ME/CFS, depressed patients, and healthy controls. After exercise, healthy people showed a much stronger increase in brain activity (218%), while ME/CFS patients showed a weaker increase (126%), suggesting their brains may not respond as vigorously to physical exertion as they should.

ME/CFS (general)

E3 PreliminaryReviewPEM not requiredReview-Narrative

Fatigue in the chronic fatigue syndrome: a cognitive phenomenon?

Fry, A M, Martin, M·Journal of psychosomatic research·1996

This 1996 study examined whether the extreme tiredness experienced by people with ME/CFS comes from problems in the muscles or the brain's motor control. After reviewing existing research on muscle function and brain activity, the researchers concluded that the fatigue is not caused by physical muscle damage or weakness. Instead, they suggest that the brain may be processing fatigue signals in an unusual way, influenced by how people think about and interpret their symptoms.

ME/CFS (general)

E3 PreliminaryMechanismPEM not requiredObservational

Effort syndrome: hyperventilation and reduction of anaerobic threshold.

Nixon, P G·Biofeedback and self-regulation·1994

This study focuses on a condition called 'effort syndrome,' which causes people to feel exhausted during physical activity. The researchers found that patients with effort syndrome breathe too heavily (hyperventilate), which changes the chemistry of their blood and makes their muscles tire much earlier than normal. By measuring breathing patterns during exercise, doctors can identify how much work each patient can do before their body runs out of chemical buffers.

ME/CFS (general)

E3 PreliminaryBehavioralPEM unclearConference-Abstract

Muscle histopathology and physiology in chronic fatigue syndrome.

Edwards, R H, Gibson, H, Clague, J E et al.·Ciba Foundation symposium·1993

Researchers examined muscle tissue from 108 ME/CFS patients and 22 healthy people using microscopes to look for structural damage, and tested muscle strength before and after exercise. They found no consistent muscle damage that explained fatigue symptoms, and muscle strength worked normally even after exercise. The study suggests ME/CFS is not caused by a primary muscle disease.

ME/CFS (general)

E3 PreliminaryReviewPEM requiredReview-Narrative

Clinical presentation of chronic fatigue syndrome.

Komaroff, A L·Ciba Foundation symposium·1993

ME/CFS is a long-lasting illness that causes severe tiredness lasting at least six months, along with other symptoms like fever, sore throat, joint pain, and worsening after physical activity. While some symptoms can look like mental health conditions, ME/CFS has physical features—like sudden onset following a flu-like illness and post-exertional exhaustion—that suggest it involves real biological problems. This condition significantly impacts people's ability to work, study, and care for themselves.

ME/CFS (general)

E3 PreliminaryMechanismPEM unclearObservational

Skeletal muscle metabolism in the chronic fatigue syndrome. In vivo assessment by 31P nuclear magnetic resonance spectroscopy.

Wong, R, Lopaschuk, G, Zhu, G et al.·Chest·1992

This study used a special imaging technique (31P NMR spectroscopy) to examine how muscles use energy during exercise in people with ME/CFS compared to healthy volunteers. Patients with ME/CFS became exhausted much faster during exercise (about 8 minutes versus 11 minutes) and had lower levels of ATP, the main energy molecule muscles use. The patterns of energy use looked similar between groups, but happened much more quickly in the ME/CFS group.

ME/CFS (general)

E3 PreliminaryReviewPEM not requiredReview-Narrative

Chronic fatigue syndrome.

McCluskey, D R, Riley, M S·Comprehensive therapy·1992

ME/CFS likely involves multiple different problems happening in the body at the same time, rather than one single cause. Most patients get sick after a viral infection, but scientists haven't found clear evidence the virus stays in the body long-term. People with ME/CFS have real physical limitations in how much exercise they can do, and they may perceive their own effort and tiredness differently than healthy people do.

ME/CFS (general)

E3 PreliminaryCommentaryPEM not requiredEditorial

Chronic fatigue syndrome: issues in the diagnosis and estimation of incidence.

Armon, C, Kurland, L T·Reviews of infectious diseases·1991

This article examines how ME/CFS is diagnosed and points out problems with the current definition used by doctors. The authors identified several issues: the definition doesn't clearly address what happens when patients do too much activity, it doesn't specify how much rest is needed, and it may miss cases in poorer communities. They suggest a new flowchart that could help identify different types of ME/CFS and potentially help some patients avoid developing the condition.

ME/CFS (general)

E3 PreliminaryReviewPEM not requiredReview-Narrative

Physiologic measurement of exercise and fatigue with special reference to chronic fatigue syndrome.

Lewis, S F, Haller, R G·Reviews of infectious diseases·1991

This review article explains how scientists measure exercise capacity and fatigue in the body. It describes three key concepts: aerobic fitness (how efficiently your heart and muscles use oxygen), muscle strength (your muscles' ability to produce force), and fatigue (the loss of strength that happens during activity). The authors discuss how these measurements might help us better understand what happens in ME/CFS when patients experience excessive fatigue.

ME/CFS (general)

Or browse by topic

PEM Immune Neuro Metabolic Biomarkers Severe ME Long COVID Cognitive

Curated Collections

Thematic groupings by clinical question or research area.

Neuroinflammation Evidence

PET imaging and other studies providing evidence for brain inflammation in ME/CFS.

Metabolism & Mitochondria

Metabolomics and mitochondrial function studies revealing energy metabolism disruption.

Biomarkers

Studies identifying potential biological markers for ME/CFS diagnosis and stratification.

PEM-Specific Research

Studies specifically examining post-exertional malaise, the hallmark symptom of ME/CFS.