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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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© 2026 ME/CFS Atlas

ME/CFS Evidence Browser — Classified Studies on Myalgic Encephalomyelitis

Evidence browser

Search and filter 6,167 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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737 studies

E0 — Consensus643E1 — Replicated320E2 — Moderate2,782E3 — Preliminary2,422

ME/CFS4,025Long COVID217Post-infectious189Overlapping1,050

Required for diagnosis414Not specified / unclear2,219Not required3,534

Post-Exertional Malaise1,064Cognitive Dysfunction1,735Pain1,620Unrefreshing Sleep799Orthostatic Intolerance478

Cytokines818Gene Expression567Metabolomics473Neuroimaging468Autoantibodies458

Infection-Triggered1,174Long COVID Overlap588Pediatric493Severe231

Strong Phenotyping438Sex-Stratified326Severe ME Included118

Systematic Review265Meta-Analysis60RCT300

Peer-reviewed6,110Preprint3Unclear54

421–440 of 737 studies

E2 ModerateCohortPEM not requiredCross-Sectional

The effect of exercise on gait and balance in patients with chronic fatigue syndrome.

Paul, L M, Wood, L, Maclaren, W·Gait & posture·2001

This study looked at whether people with ME/CFS have problems with walking and balance, and whether light exercise makes these problems worse. Researchers compared 11 ME/CFS patients with 11 healthy people and found that while ME/CFS patients did show different walking patterns, their balance was similar to healthy controls, and the exercise test did not worsen either group's balance or gait.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredObservational

Identifying physical activity patterns in chronic fatigue syndrome using actigraphic assessment.

van der Werf, S P, Prins, J B, Vercoulen, J H et al.·Journal of psychosomatic research·2000

Researchers used a motion-tracking device to measure physical activity patterns in 277 ME/CFS patients over 12 days and compared them to 47 healthy people. Patients with ME/CFS showed less intense bursts of activity, shorter activity periods, and longer rest times afterward. About one-fourth of patients were identified as 'pervasively passive'—meaning they had very low activity levels throughout the entire study period.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Exercise capacity in chronic fatigue syndrome.

De Becker, P, Roeykens, J, Reynders, M et al.·Archives of internal medicine·2000

This study measured how much exercise women with ME/CFS could tolerate compared to healthy women without the condition. Patients with ME/CFS were able to exercise at only about half the capacity of healthy controls—they couldn't reach high heart rates and couldn't sustain heavy workloads. The findings show that ME/CFS significantly limits physical ability in ways that can be objectively measured.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Normal carnitine levels in patients with chronic fatigue syndrome.

Soetekouw, P M, Wevers, R A, Vreken, P et al.·The Netherlands journal of medicine·2000

This study tested whether a chemical called carnitine, which helps muscles produce energy, was missing in people with ME/CFS. Researchers measured carnitine levels in 25 women with ME/CFS and compared them to 25 healthy women. They found that carnitine levels were actually normal in the ME/CFS patients, which contradicted earlier studies that suggested carnitine deficiency might cause the condition.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Influence of exhaustive treadmill exercise on cognitive functioning in chronic fatigue syndrome.

LaManca, J J, Sisto, S A, DeLuca, J et al.·The American journal of medicine·1998

This study looked at how exercise affects thinking and mental processing in people with ME/CFS compared to healthy people. Both groups did exhausting exercise on a treadmill, then took thinking tests right after and 24 hours later. People with ME/CFS performed worse on these thinking tests after exercise, particularly on tasks involving speed and attention, and their thinking stayed impaired the next day.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearCross-Sectional

Effects of exercise on cognitive and motor function in chronic fatigue syndrome and depression.

Blackwood, S K, MacHale, S M, Power, M J et al.·Journal of neurology, neurosurgery, and psychiatry·1998

This study compared how people with ME/CFS, people with depression, and healthy people performed on thinking and strength tests before and after exercise on a treadmill. People with ME/CFS reported feeling much more tired and struggling harder during the exercise than the other groups. After exercising, people with ME/CFS had bigger drops in their ability to focus and pay attention compared to healthy people, suggesting that exercise affects their thinking ability in a specific way.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Muscle fibre characteristics and lactate responses to exercise in chronic fatigue syndrome.

Lane, R J, Barrett, M C, Woodrow, D et al.·Journal of neurology, neurosurgery, and psychiatry·1998

Researchers examined muscle samples from 105 ME/CFS patients to understand why they have abnormal responses to exercise, particularly high lactate levels. They found that patients with high lactate responses had fewer type 1 muscle fibres (which are energy-efficient), but this wasn't because they were inactive—it appeared to be a specific muscle problem related to ME/CFS itself.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCase-Control

[Risk factors for ischemic heart disease in patients with chronic fatigue syndrome].

Vilikus, Z, Marecková, H, Janatková, I et al.·Sbornik lekarsky·1998

This study compared heart disease risk factors between people with ME/CFS and healthy controls. Researchers found that despite ME/CFS patients exercising less overall, they had no higher risk for heart disease than the control group. This suggests that reduced exercise activity in ME/CFS does not appear to increase cardiovascular risk in the way it might in other conditions.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearObservational

Physical activity before and after exercise in women with chronic fatigue syndrome.

Sisto, S A, Tapp, W N, LaManca, J J et al.·QJM : monthly journal of the Association of Physicians·1998

This study tracked the physical activity of 20 women with ME/CFS and 20 healthy volunteers for two weeks using a movement monitor worn at the waist. After all participants did a strenuous treadmill exercise test, researchers measured how their activity changed. Women with ME/CFS showed a noticeable drop in activity levels after the exercise, with the biggest decrease happening around days 12-14, and they took more rest breaks during the day.

Post-Exertional Malaise

E2 ModerateBehavioralPEM not requiredCross-Sectional

Physical fatigability and exercise capacity in chronic fatigue syndrome: association with disability, somatization and psychopathology.

Fischler, B, Dendale, P, Michiels, V et al.·Journal of psychosomatic research·1997

This study looked at how people with ME/CFS respond to exercise by measuring whether they can reach their target heart rate during activity. Researchers found that many patients don't reach expected heart rates and that this relates to how disabled they feel in daily life. Interestingly, anxiety and depression didn't explain why people avoided strenuous exercise, suggesting that avoidance behavior in ME/CFS may have different causes than in other conditions.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCase-Control

A case-control study to assess possible triggers and cofactors in chronic fatigue syndrome.

MacDonald, K L, Osterholm, M T, LeDell, K H et al.·The American journal of medicine·1996

This study compared 47 people with ME/CFS to 47 matched healthy controls to identify what might trigger or contribute to the illness. Researchers found that people with ME/CFS were more likely to have exercised regularly before getting sick, and women with ME/CFS were more likely to have never had children. Depression was more common after ME/CFS developed, though it wasn't more common before illness onset.

Post-Exertional Malaise

E2 ModerateCohortPEM requiredCross-Sectional

Decreased vagal power during treadmill walking in patients with chronic fatigue syndrome.

Cordero, D L, Sisto, S A, Tapp, W N et al.·Clinical autonomic research : official journal of the Clinical Autonomic Research Society·1996

This study compared how the nervous system controls heart rate in people with ME/CFS versus healthy volunteers during and after treadmill walking. Researchers found that people with ME/CFS had weaker parasympathetic (rest-and-recover) nervous system activity during walking, and this activity dropped even further after exercise stopped. This abnormality might help explain why ME/CFS patients feel worse after physical activity.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCase-Control

An examination of the working case definition of chronic fatigue syndrome.

Komaroff, A L, Fagioli, L R, Geiger, A M et al.·The American journal of medicine·1996

Researchers studied 281 patients with severe, long-lasting fatigue to see how well the official definition of ME/CFS worked. They compared these patients to healthy people and people with similar conditions like multiple sclerosis and depression. The study found that certain symptoms—like muscle pain, post-exertion exhaustion, headaches, and flu-like symptoms—were very common in ME/CFS patients but rare in the other groups.

Post-Exertional Malaise

E2 ModerateBehavioralPEM not requiredCase-Control

Psychological symptoms, somatic symptoms, and psychiatric disorder in chronic fatigue and chronic fatigue syndrome: a prospective study in the primary care setting.

Wessely, S, Chalder, T, Hirsch, S et al.·The American journal of psychiatry·1996

This study followed over 1,900 people in primary care and found that most individuals with ME/CFS also had a current mental health condition like depression or anxiety. The researchers discovered that people with chronic fatigue were much more likely to have psychiatric disorders (60-78%) compared to those without fatigue (19-31%). While the study suggests a strong link between psychiatric conditions and ME/CFS, it does not explain whether one causes the other.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Metabolic and cardiovascular effects of a progressive exercise test in patients with chronic fatigue syndrome.

Sisto, S A, LaManca, J, Cordero, D L et al.·The American journal of medicine·1996

Researchers tested how well women with ME/CFS could exercise compared to healthy controls by having them walk on a treadmill until exhaustion. Women with ME/CFS had lower aerobic fitness levels than healthy controls, but their hearts and lungs appeared to work normally. Importantly, the maximal exercise test did not cause a major flare-up of fatigue or other ME/CFS symptoms.

Post-Exertional Malaise

E2 ModerateBehavioralPEM not requiredCross-Sectional

The impact of catastrophic beliefs on functioning in chronic fatigue syndrome.

Petrie, K, Moss-Morris, R, Weinman, J·Journal of psychosomatic research·1995

This study looked at whether how people think about ME/CFS affects how disabled they become. Researchers asked 282 people with ME/CFS what they thought would happen if they pushed themselves too hard, and sorted their answers into catastrophic (very negative) or non-catastrophic thinking. People who had catastrophic thoughts about pushing themselves were significantly more fatigued and more disabled in work, household tasks, sleep, socializing, and hobbies—even though they had been sick for similar lengths of time as others.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Repetitively negative changing T waves at 24-h electrocardiographic monitors in patients with the chronic fatigue syndrome. Left ventricular dysfunction in a cohort.

Lerner, A M, Lawrie, C, Dworkin, H S·Chest·1993

This study looked at heart activity recorded over 24 hours in ME/CFS patients compared to others. All 24 ME/CFS patients showed unusual patterns on their heart monitors (abnormal T waves), compared to only 22% of people without ME/CFS. Further testing found that 8 out of 60 ME/CFS patients had mild heart pumping problems that only showed up during exercise, even though their resting heart function appeared normal. The researchers suggest ME/CFS fatigue might be related to the heart not working well during normal daily activities.

Post-Exertional Malaise

E2 ModerateReviewPEM unclearReview-Narrative

Symptoms and signs of chronic fatigue syndrome.

Komaroff, A L, Buchwald, D·Reviews of infectious diseases·1991

This review summarizes what doctors have learned about chronic fatigue syndrome (ME/CFS) by studying approximately 510 patients. The hallmark features include a sudden illness-like onset, long-lasting exhaustion that severely limits daily activities, and a unique symptom called postexertional malaise—where patients feel much worse after physical or mental activity. Many patients also experience fever, sore throat, swollen lymph nodes, muscle pain, sleep problems, and difficulty concentrating.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearCross-Sectional

Aerobic work capacity in patients with chronic fatigue syndrome.

Riley, M S, O'Brien, C J, McCluskey, D R et al.·BMJ (Clinical research ed.)·1990

This study tested how much physical activity patients with ME/CFS could manage on a treadmill and compared them to healthy people and those with irritable bowel syndrome. Researchers found that ME/CFS patients got tired much faster, had higher heart rates during exercise, and felt like they were working much harder than the other groups—even though they weren't doing as much activity.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Cardiac function at rest and with exercise in the chronic fatigue syndrome.

Montague, T J, Marrie, T J, Klassen, G A et al.·Chest·1989

This study looked at heart function in 41 ME/CFS patients compared to healthy volunteers. While the hearts looked normal at rest, patients became exhausted during exercise much sooner than healthy people—their heart rates climbed more slowly and didn't reach the expected levels, even though their resting heart rhythms and structure were completely normal.

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.