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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 6,113 studies by evidence level, diagnostic criteria, PEM status, and research domain. Each entry links to the original source.

Studies sorted by review quality. 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 — Consensus629E1 — Replicated320E2 — Moderate2,745E3 — Preliminary2,419

ME/CFS4,003Long COVID206Post-infectious189Overlapping1,031

Required for diagnosis410Not specified / unclear2,176Not required3,527

Post-Exertional Malaise1,039Cognitive Dysfunction1,709Pain1,606Unrefreshing Sleep785Orthostatic Intolerance468

Cytokines812Gene Expression566Metabolomics468Neuroimaging463Autoantibodies454

Infection-Triggered1,155Long COVID Overlap562Pediatric491Severe226

Strong Phenotyping427Sex-Stratified325Severe ME Included114

Systematic Review258Meta-Analysis59RCT300

Higher42Moderate2,570Preliminary3,224Weak277

Peer-reviewed6,056Preprint3Unclear54

121–140 of 260 studies

E2 ModeratePEM unclearModerate confidenceObservationalEditor reviewed

Impact of a maximal exercise test on symptoms and activity in chronic fatigue syndrome.

Bazelmans, Ellen, Bleijenberg, Gijs, Voeten, Marinus J M et al.·Journal of psychosomatic research·2005

This study tested how a single intense exercise session affected people with ME/CFS compared to healthy controls. People with ME/CFS experienced increased fatigue that lasted up to 2 days after the exercise test, while healthy people felt back to normal within 2 hours. Interestingly, people with ME/CFS didn't actually move around less after the exercise—their fatigue increased even though their measured activity stayed the same.

ME/CFS (general)

E2 ModeratePEM not requiredPreliminaryObservationalEditor reviewed

Increased daily physical activity and fatigue symptoms in chronic fatigue syndrome.

Black, Christopher D, O'connor, Patrick J, McCully, Kevin K·Dynamic medicine : DM·2005

This small study asked 6 people with ME/CFS to increase their daily walking by about 30% for 4 weeks and tracked how they felt. Unlike some previous research suggesting exercise helps, these patients reported that their muscle pain and mood actually got worse with more activity, even though they were able to increase their activity level. The researchers suggest that people with ME/CFS may have a daily limit to how much activity they can do before symptoms worsen.

ME/CFS (general)

E2 ModeratePEM not requiredModerate confidenceObservationalEditor reviewed

Kinesiophobia in chronic fatigue syndrome: assessment and associations with disability.

Nijs, Jo, De Meirleir, Kenny, Duquet, William·Archives of physical medicine and rehabilitation·2004

This study looked at whether ME/CFS patients who fear movement (kinesiophobia) have more activity limitations than others. Researchers used a questionnaire to measure fear of movement and found that patients with higher fear of movement reported more difficulty with daily activities, but this fear did not actually relate to how much exercise capacity they had when tested on a bike.

ME/CFS (general)

E2 ModeratePEM unclearPreliminaryReview-NarrativeEditor reviewed

Chronic fatigue syndrome: matching exercise to symptom fluctuations.

Skinner, James S·The Physician and sportsmedicine·2004

People with ME/CFS often feel extremely tired and experience worsening fatigue after physical activity, leading many to stop exercising altogether and become weaker. This review suggests that gentle, intermittent exercise at low to moderate intensity may actually help improve how much activity patients can do and reduce their fatigue and other symptoms. The good news is that standard exercise testing doesn't make ME/CFS symptoms worse, and matching exercise type to daily symptom changes appears to be a practical approach.

ME/CFS (general)

E2 ModeratePEM not requiredModerate confidenceCase-ControlEditor reviewed

Physiological responses during a submaximal cycle test in chronic fatigue syndrome.

Wallman, Karen E, Morton, Alan R, Goodman, Carmel et al.·Medicine and science in sports and exercise·2004

This study compared how people with ME/CFS and healthy people without the condition respond to exercise on a stationary bike. The main finding was that people with ME/CFS felt much more exhausted during the same amount of exercise, and they couldn't exercise as hard before becoming tired. Both groups were matched carefully so they had similar activity levels before the study, which makes the comparison more fair.

ME/CFS (general)

E2 ModeratePEM not requiredModerate confidenceCross-SectionalEditor reviewed

Sociodemographic and symptom correlates of fatigue in an adolescent primary care sample.

Mears, Cynthia J, Taylor, Renee R, Jordan, Karen M et al.·The Journal of adolescent health : official publication of the Society for Adolescent Medicine·2004

This study looked at how common fatigue lasting more than one month is in teenagers visiting primary care clinics. Researchers found that about 8% of teens had prolonged fatigue and 4.4% had symptoms matching CFS-like illness. Teens with prolonged fatigue were more likely to also experience headaches, muscle pain, fever, and fatigue that worsened with exercise.

ME/CFS (general)

E2 ModeratePEM not requiredModerate confidenceCase-ControlEditor reviewed

Perceived exertion in fatiguing illness: Gulf War veterans with chronic fatigue syndrome.

Cook, Dane B, Nagelkirk, Paul R, Peckerman, Arnold et al.·Medicine and science in sports and exercise·2003

This study compared how hard exercise felt to Gulf War veterans with ME/CFS versus healthy Gulf War veterans. Researchers had both groups exercise on stationary bikes while measuring their effort ratings. People with ME/CFS reported that the same amount of exercise felt much harder than it did for healthy veterans, even though they had similar physical fitness levels.

ME/CFS (general)

E2 ModeratePEM requiredPreliminaryCross-SectionalEditor reviewed

Rupture of silicone gel breast implants and symptoms of pain and fatigue.

Vermeulen, Ruud C W, Scholte, Hans R·The Journal of rheumatology·2003

This study looked at women with silicone breast implants to see if their symptoms matched those of ME/CFS patients. Researchers found that women whose implants had ruptured reported more severe fatigue, pain, and memory problems than those with intact implants. While the symptom patterns differed somewhat from typical ME/CFS, rupture of the implant was associated with worsening of fatigue and pain symptoms.

ME/CFS (general)

E2 ModeratePEM not requiredModerate confidenceCross-SectionalEditor reviewed

Perceived exertion in fatiguing illness: civilians with chronic fatigue syndrome.

Cook, Dane B, Nagelkirk, Paul R, Peckerman, Arnold et al.·Medicine and science in sports and exercise·2003

This study looked at how hard exercise feels to people with ME/CFS compared to healthy people. Researchers had both groups exercise on a treadmill and rate their effort. While people with ME/CFS said exercise felt harder at moderate intensities, when researchers compared effort levels to each person's maximum oxygen capacity, there was no real difference—suggesting the difference in how hard it felt might be explained by their lower fitness level rather than a problem with how their body perceives effort.

ME/CFS (general)

E2 ModeratePEM not requiredModerate confidenceCross-SectionalEditor reviewed

Subclassifying chronic fatigue syndrome through exercise testing.

Vanness, J Mark, Snell, Christopher R, Strayer, David R et al.·Medicine and science in sports and exercise·2003

Researchers tested 189 people with ME/CFS using an exercise test that measures how much oxygen the body can use. They sorted patients into four groups based on fitness level—from no impairment to severe. The study found that people with ME/CFS vary widely in their physical capacity, and that fitness level affects how the body responds to exercise in measurable ways.

ME/CFS (general)

E2 ModeratePEM not requiredModerate confidenceCross-SectionalEditor reviewed

Blood volume and its relation to peak O(2) consumption and physical activity in patients with chronic fatigue.

Farquhar, William B, Hunt, Brian E, Taylor, J Andrew et al.·American journal of physiology. Heart and circulatory physiology·2002

This study looked at whether people with ME/CFS have lower blood volume (the amount of fluid circulating in their bodies) and whether this might explain their exercise problems. Researchers compared 17 ME/CFS patients with 17 healthy controls, measuring blood volume and fitness capacity. They found that ME/CFS patients had significantly reduced exercise capacity and a trend toward lower blood volume, and these two measurements were strongly related to each other.

ME/CFS (general)

E2 ModeratePEM unclearModerate confidenceCross-SectionalEditor reviewed

Cardiovascular responses of women with chronic fatigue syndrome to stressful cognitive testing before and after strenuous exercise.

LaManca, J J, Peckerman, A, Sisto, S A et al.·Psychosomatic medicine·2001

This study compared how the hearts and blood pressure of women with ME/CFS respond to stressful mental tasks compared to healthy women. Researchers found that women with ME/CFS had a weaker cardiovascular response to cognitive stress than healthy controls, and this pattern held true even after exercise. The study also found that women with more severe ME/CFS symptoms had the lowest cardiovascular responses to stress.

ME/CFS (general)

E2 ModeratePEM not requiredModerate confidenceCross-SectionalEditor reviewed

Is physical deconditioning a perpetuating factor in chronic fatigue syndrome? A controlled study on maximal exercise performance and relations with fatigue, impairment and physical activity.

Bazelmans, E, Bleijenberg, G, Van Der Meer, J W et al.·Psychological medicine·2001

This study tested whether ME/CFS patients are in poor physical condition compared to healthy people, and whether being out of shape might be making their illness worse. Researchers had 20 ME/CFS patients and 20 healthy controls perform exercise tests while measuring heart rate, oxygen use, and other body functions. The study found no significant difference in physical fitness between the two groups, suggesting that poor fitness is not the main reason ME/CFS patients struggle with exercise.

ME/CFS (general)

E2 ModeratePEM not requiredPreliminaryCase-ControlEditor reviewed

Cognitive compromise following exercise in monozygotic twins discordant for chronic fatigue syndrome: fact or artifact?

Claypoole, K, Mahurin, R, Fischer, M E et al.·Applied neuropsychology·2001

This study asked whether exercise makes thinking and memory problems worse in people with ME/CFS. Researchers tested 21 pairs of identical twins where one twin had ME/CFS and one did not, asking them to exercise until exhausted and then testing their memory, attention, and thinking speed. The twins with ME/CFS did not show worse cognitive decline after exercise compared to their healthy twin, suggesting that exercise itself does not damage thinking ability.

ME/CFS (general)

E2 ModeratePEM not requiredPreliminaryCross-SectionalEditor reviewed

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.

ME/CFS (general)

E2 ModeratePEM not requiredModerate confidenceCross-SectionalEditor reviewed

Physiological responses to incremental exercise in patients with chronic fatigue syndrome.

Inbar, O, Dlin, R, Rotstein, A et al.·Medicine and science in sports and exercise·2001

Researchers compared how the bodies of 15 people with ME/CFS responded to a gradually increasing exercise test on a treadmill, compared to 15 healthy people. People with ME/CFS showed lower heart rates and weaker cardiovascular responses during exercise, even when they appeared to be pushing themselves as hard as they could. This suggests their bodies may have trouble with either heart function or muscle oxygen use during physical exertion.

ME/CFS (general)

E2 ModeratePEM not requiredModerate confidenceObservationalEditor reviewed

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.

ME/CFS (general)

E2 ModeratePEM not requiredModerate confidenceCross-SectionalEditor reviewed

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.

ME/CFS (general)

E2 ModeratePEM not requiredModerate confidenceCross-SectionalEditor reviewed

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.

ME/CFS (general)

E2 ModeratePEM unclearModerate confidenceCross-SectionalEditor reviewed

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.

ME/CFS (general)

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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.