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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.

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ME/CFS Evidence Browser — Classified Studies on Myalgic Encephalomyelitis

Evidence browser

Search and filter 6,188 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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742 studies

E0 — Consensus649E1 — Replicated321E2 — Moderate2,795E3 — Preliminary2,423

ME/CFS4,032Long COVID222Post-infectious189Overlapping1,058

Required for diagnosis416Not specified / unclear2,235Not required3,537

Post-Exertional Malaise1,074Cognitive Dysfunction1,744Pain1,625Unrefreshing Sleep802Orthostatic Intolerance482

Cytokines820Gene Expression570Metabolomics476Neuroimaging471Autoantibodies458

Infection-Triggered1,178Long COVID Overlap597Pediatric494Severe232

Strong Phenotyping443Sex-Stratified328Severe ME Included119

Systematic Review269Meta-Analysis61RCT301

Peer-reviewed6,131Preprint3Unclear54

701–720 of 742 studies

E3 PreliminaryMechanismPEM requiredMechanistic

Exercise lowers pain threshold in chronic fatigue syndrome.

Whiteside, Alan, Hansen, Stig, Chaudhuri, Abhijit·Pain·2004

This study looked at how exercise affects pain sensitivity in people with ME/CFS compared to healthy people. When healthy volunteers exercised, their pain threshold (the point at which they felt pain) went up, making them less sensitive to pain. However, in ME/CFS patients, the pain threshold actually decreased after exercise, meaning they became more sensitive to pain. This suggests that the body's natural pain-blocking system may not work properly in ME/CFS.

Post-Exertional Malaise

E3 PreliminaryMechanismPEM not requiredMechanistic

Chronic fatigue syndrome: new evidence for a central fatigue disorder.

Georgiades, Evelina, Behan, Wilhelmina M H, Kilduff, Liam P et al.·Clinical science (London, England : 1979)·2003

This study investigated whether ME/CFS involves problems with how the brain regulates energy and effort perception. Researchers compared 12 ME/CFS patients and 11 healthy controls during exercise, measuring chemicals in the blood that help the brain function. ME/CFS patients felt more exhausted at every stage and had different levels of brain chemicals, particularly those related to serotonin and dopamine—systems that regulate mood, motivation, and perception of effort.

Post-Exertional Malaise

E3 PreliminaryMechanismPEM not requiredCross-Sectional

Hypothalamic-pituitary-adrenal axis reactivity in chronic fatigue syndrome and health under psychological, physiological, and pharmacological stimulation.

Gaab, Jens, Hüster, Dominik, Peisen, Renate et al.·Psychosomatic medicine·2002

This study looked at how the stress-response system (a hormone system in the brain called the HPA axis) works in ME/CFS patients compared to healthy people. Researchers exposed both groups to different types of stress—mental stress, exercise, and a hormone test—and measured how their bodies responded. ME/CFS patients showed lower levels of a stress hormone called ACTH at baseline and during stress tests, but their cortisol levels were mostly normal, suggesting their stress system works differently rather than being broken.

Post-Exertional Malaise

E3 PreliminaryReviewPEM unclearReview-Narrative

Chronic fatigue syndrome: probable pathogenesis and possible treatments.

Evengård, Birgitta, Klimas, Nancy·Drugs·2002

ME/CFS is a serious illness affecting about 1 in 200 people in Western countries, causing extreme tiredness that lasts at least 6 months along with problems thinking clearly, poor sleep, and pain. While doctors don't yet know exactly what causes it, research shows the immune system is overactive and certain brain functions are disrupted. Currently, talking therapy (cognitive behavioural therapy) can help improve quality of life, but scientists are still searching for more effective treatments.

Immune SystemPost-Exertional Malaise

E3 PreliminaryReviewPEM not requiredReview-Narrative

Cytokine responses to physical activity, with particular reference to IL-6: sources, actions, and clinical implications.

Shephard, Roy J·Critical reviews in immunology·2002

When people exercise, their muscles release a protein called IL-6 that helps control inflammation and manage energy. This review examines how the body produces different types of inflammatory signals during and after exercise, with IL-6 playing a central role. The authors note that people with ME/CFS have higher levels of these inflammatory proteins, though it's unclear whether these proteins actually cause the fatigue experienced by patients.

Immune SystemPost-Exertional Malaise

E3 PreliminaryReviewPEM unclearReview-Narrative

Chronic fatigue syndrome: evaluation and treatment.

Craig, Timothy, Kakumanu, Sujani·American family physician·2002

ME/CFS is a serious condition marked by extreme tiredness that doesn't go away, along with muscle pain, swollen lymph nodes, and feeling worse after physical activity. Doctors diagnose it mainly by ruling out other illnesses, since there's no single blood test or physical sign that definitively confirms it. Treatment is personalized and may include exercise, sleep improvements, diet changes, and medications like antidepressants.

Post-Exertional Malaise

E3 PreliminaryMechanismPEM requiredMechanistic

Activity rhythm degrades after strenuous exercise in chronic fatigue syndrome.

Ohashi, Kyoko, Yamamoto, Yoshiharu, Natelson, Benjamin H·Physiology & behavior·2002

This study looked at whether exhausting exercise disrupts the body's internal daily rhythm in people with ME/CFS. Researchers measured activity patterns in ME/CFS patients and healthy controls before and after a strenuous treadmill test. They found that ME/CFS patients' activity rhythms became abnormally lengthened (longer than 24 hours) after exercise, while healthy people's rhythms stayed normal—suggesting the body loses its ability to keep time after strenuous activity in ME/CFS.

Post-Exertional Malaise

E3 PreliminaryReviewPEM not requiredReview-Narrative

The case definition of chronic fatigue syndrome.

Tan, Eng M, Sugiura, Kazumitsu, Gupta, Sudhir·Journal of clinical immunology·2002

This review discusses how ME/CFS is currently diagnosed using symptom-based criteria from 1994, which doesn't account for the fact that different patients have very different experiences. The authors suggest that ME/CFS might actually be four distinct subtypes based on which body system is most affected: nervous system (memory problems, headaches), endocrine system (poor sleep, post-exertion crashes), musculoskeletal system (muscle and joint pain), or immune/infection-related (sore throat, swollen lymph nodes). If researchers studied more similar groups of patients separately instead of mixing everyone together, they might get clearer and more consistent results.

Post-Exertional Malaise

E3 PreliminaryMechanismPEM requiredObservational

Hormonal responses to exercise in chronic fatigue syndrome.

Ottenweller, J E, Sisto, S A, McCarty, R C et al.·Neuropsychobiology·2001

This study compared how the bodies of ME/CFS patients and healthy people respond to exercise, specifically looking at hormones—chemical messengers that regulate many body functions. Researchers found that ME/CFS patients had weaker responses in several key stress hormones (like adrenaline) immediately after exercise, but hormone levels returned to normal by the next day, suggesting that abnormal hormones may not be the main reason why ME/CFS patients feel worse after exertion.

Post-Exertional Malaise

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.

Post-Exertional Malaise

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.

Post-Exertional Malaise

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.

Post-Exertional Malaise

E3 PreliminaryMechanismPEM unclearCase-Control

Immunological response in chronic fatigue syndrome following a graded exercise test to exhaustion.

LaManca, J J, Sisto, S A, Zhou, X D et al.·Journal of clinical immunology·1999

Researchers tested whether people with ME/CFS have an unusual immune system response to hard exercise compared to healthy people who don't exercise regularly. They had 20 women with ME/CFS and 14 healthy women do an exhausting treadmill test, then checked their blood for immune cells and immune chemicals at several time points. While people with ME/CFS reported much worse fatigue 24 hours later, their immune systems actually responded to the exercise in the same way as the healthy controls.

Immune SystemPost-Exertional Malaise

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.

Post-Exertional Malaise

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.

Post-Exertional Malaise

E3 PreliminaryCommentaryPEM not requiredEditorial

Chronic fatigue syndrome: new insights and old ignorance.

Evengård, B, Schacterle, R S, Komaroff, A L·Journal of internal medicine·1999

ME/CFS is a complex condition that affects thinking, sleep quality, and causes physical symptoms like sore throats, muscle pain, and exhaustion after activity. While many patients report that their illness began with an infection, scientists still don't fully understand how infections connect to ME/CFS. Research shows the immune system is overactive and certain brain systems aren't working normally, suggesting ME/CFS involves multiple body systems.

Immune SystemPost-Exertional Malaise

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.

Post-Exertional Malaise

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.

Post-Exertional Malaise

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.

Post-Exertional Malaise

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.

Post-Exertional Malaise

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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.