Skip to content

Start Here
Atlas
Evidence
Research
Ask
Updates
About
Support

Evidence Atlas

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

Start Here
Atlas
Evidence
Research
Ask
FAQ
Glossary
Updates
Methodology
Press
Retractions
Contribute
About
Support
Contact

Weekly research digest — no spam

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.

Generator v1·Scanner v1.4·Lint gate: enforce·See methodology

© 2026 ME/CFS Atlas

ME/CFS Evidence Browser — Classified Studies on Myalgic Encephalomyelitis

Evidence browser

Search and filter 6,145 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 →

Sort

345 studies

E0 — Consensus637E1 — Replicated320E2 — Moderate2,768E3 — Preliminary2,420

ME/CFS4,014Long COVID212Post-infectious189Overlapping1,045

Required for diagnosis412Not specified / unclear2,201Not required3,532

Post-Exertional Malaise1,055Cognitive Dysfunction1,723Pain1,612Unrefreshing Sleep793Orthostatic Intolerance474

Cytokines816Gene Expression567Metabolomics469Neuroimaging466Autoantibodies457

Infection-Triggered1,170Long COVID Overlap580Pediatric492Severe228

Strong Phenotyping435Sex-Stratified326Severe ME Included116

Systematic Review263Meta-Analysis60RCT300

Peer-reviewed6,088Preprint3Unclear54

181–200 of 345 studies

E2 ModerateCohortPEM not requiredCross-Sectional

Small heart syndrome in patients with chronic fatigue syndrome.

Miwa, Kunihisa, Fujita, Masatoshi·Clinical cardiology·2008

This study found that people with ME/CFS are more likely to have a smaller heart than healthy people. Researchers used chest X-rays and heart ultrasounds to measure heart size in 56 ME/CFS patients under age 50 and compared them to 38 healthy controls. Patients with both ME/CFS and a small heart also experienced more symptoms like dizziness when standing, cold feet, and heart rhythm irregularities.

Autonomic Nervous System

E2 ModerateCohortPEM unclearCross-Sectional

Electrocardiographic QT interval and cardiovascular reactivity in fibromyalgia differ from chronic fatigue syndrome.

Naschitz, Jochanan E, Slobodin, Gleb, Sharif, Dauod et al.·European journal of internal medicine·2008

This study found that ME/CFS and fibromyalgia, two conditions that seem similar on the surface, actually show different patterns on heart tests. People with ME/CFS had shorter QT intervals on their electrocardiogram (a measure of heart electrical activity) and had more dramatic blood pressure and heart rate changes during a tilting test compared to people with fibromyalgia. These differences suggest the two conditions may be distinct disorders rather than variants of the same illness.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCross-Sectional

Sympathetic cardiovascular control during orthostatic stress and isometric exercise in adolescent chronic fatigue syndrome.

Wyller, Vegard Bruun, Saul, J Philip, Walløe, Lars et al.·European journal of applied physiology·2008

This study looked at how the bodies of adolescents with ME/CFS respond to physical stress, specifically when lying down while pressure is applied to the legs and while squeezing a hand grip. Researchers found that ME/CFS patients had higher heart rates and stress hormone levels even at rest, and their cardiovascular system overreacted to the leg pressure test but underreacted during the hand grip exercise compared to healthy teenagers.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCross-Sectional

Symptoms of autonomic dysfunction in chronic fatigue syndrome.

Newton, J L, Okonkwo, O, Sutcliffe, K et al.·QJM : monthly journal of the Association of Physicians·2007

This study looked at whether people with ME/CFS have problems with their autonomic nervous system (the part that controls automatic body functions like heart rate and blood pressure). Researchers used a questionnaire called COMPASS to measure autonomic symptoms in ME/CFS patients and healthy controls. They found that autonomic dysfunction symptoms were significantly more common in ME/CFS patients and were linked to how severe their fatigue was.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCross-Sectional

[Estimation of fatigue state in patient with CFS using actigraph and R-R interval power spectrum analysis].

Tajima, Seiki, Kuratsune, Hirohiko, Yamaguti, Kouzi et al.·Nihon rinsho. Japanese journal of clinical medicine·2007

This study measured activity levels and sleep patterns in people with ME/CFS using wearable devices and heart rate analysis. Researchers found that ME/CFS patients had lower activity during waking hours, slept longer, experienced more frequent sleep disruptions, and showed abnormal nervous system activity during sleep compared to healthy people.

SleepAutonomic Nervous System

E2 ModerateCohortPEM not requiredCase-Control

Higher heart rate and reduced heart rate variability persist during sleep in chronic fatigue syndrome: a population-based study.

Boneva, Roumiana S, Decker, Michael J, Maloney, Elizabeth M et al.·Autonomic neuroscience : basic & clinical·2007

This study found that people with ME/CFS have a faster heart rate and less heart rate variability (natural changes in heartbeat speed) during sleep compared to healthy people. These differences suggest that the nervous system in ME/CFS patients stays more activated even during sleep, which may be related to chemical imbalances in the body.

SleepAutonomic Nervous System

E2 ModerateCohortPEM not requiredCross-Sectional

Sympathetic predominance of cardiovascular regulation during mild orthostatic stress in adolescents with chronic fatigue.

Wyller, Vegard B, Saul, J P, Amlie, Jan P et al.·Clinical physiology and functional imaging·2007

This study looked at how the nervous system controls the heart and blood vessels in teenagers with ME/CFS when their bodies experience mild stress (tilting on a bed). Researchers found that adolescents with ME/CFS showed an exaggerated sympathetic nervous system response—meaning their "fight or flight" system kicked in too strongly compared to healthy teenagers. This suggests the body's automatic control of heart rate and blood pressure may not work normally in ME/CFS.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCross-Sectional

Usefulness of an abnormal cardiovascular response during low-grade head-up tilt-test for discriminating adolescents with chronic fatigue from healthy controls.

Wyller, Vegard Bruun, Due, Reidar, Saul, J Philip et al.·The American journal of cardiology·2007

This study tested how the hearts of adolescents with ME/CFS respond to mild physical stress (tilting the body slightly upright for 15 minutes) compared to healthy teenagers. Researchers found that young people with ME/CFS had abnormal heart and blood vessel responses during this test—their hearts beat faster, their blood pressure increased more, and their stroke volume (amount of blood pumped per heartbeat) decreased more than in healthy controls. These differences suggest that ME/CFS involves problems with how the body regulates blood flow and heart function during even mild stress.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCross-Sectional

Patterns of hypocapnia on tilt in patients with fibromyalgia, chronic fatigue syndrome, nonspecific dizziness, and neurally mediated syncope.

Naschitz, Jochanan E, Mussafia-Priselac, Renata, Kovalev, Yulia et al.·The American journal of the medical sciences·2006

This study looked at whether people with ME/CFS, fibromyalgia, and dizziness breathe too fast when standing up, causing them to exhale too much carbon dioxide (a condition called hypocapnia). Researchers tested 585 people using a tilt table that slowly raises the upper body while measuring breathing patterns. They found that 9-27% of people with these conditions showed abnormal breathing on the tilt test, compared to 0-2% of healthy controls, suggesting this may be a real but not universal feature of these illnesses.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCross-Sectional

Shortened QT interval: a distinctive feature of the dysautonomia of chronic fatigue syndrome.

Naschitz, Jochanan, Fields, Madeline, Isseroff, Hillel et al.·Journal of electrocardiology·2006

This study examined heart rhythm patterns in ME/CFS patients by measuring a specific electrical timing interval on EKGs (called the QT interval). Researchers found that people with ME/CFS had shorter QT intervals than healthy controls, both when lying down and during a head-up tilt test. This shortened interval appears to be linked to the autonomic nervous system problems common in ME/CFS.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCross-Sectional

Hyperventilation and amplified blood pressure response: is there a link?

Naschitz, J E, Mussafia-Priselac, R, Peck, E R et al.·Journal of human hypertension·2005

This study looked at whether rapid, shallow breathing (hyperventilation) causes blood pressure to rise when people change position, such as standing up. Researchers tested 320 patients with various conditions including ME/CFS using a tilt table test while measuring breathing CO2 levels. They found that hyperventilation during the test did not lead to higher blood pressure increases, suggesting that rapid breathing may not be the cause of blood pressure problems in these patient groups.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCase-Control

Orthostatic instability in a population-based study of chronic fatigue syndrome.

Jones, James F, Nicholson, Ainsley, Nisenbaum, Rosane et al.·The American journal of medicine·2005

This study tested whether people with ME/CFS have problems with their body's ability to regulate blood pressure and heart rate when changing positions (like standing up). Researchers compared 58 people with ME/CFS to 55 healthy people using a tilt table test. Surprisingly, they found that both groups had similar rates of these problems, suggesting that this particular type of autonomic dysfunction may not be a primary cause of ME/CFS.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCross-Sectional

Cardiovascular reactivity in fibromyalgia: evidence for pathogenic heterogeneity.

Naschitz, Jochanan E, Rozenbaum, Michael, Fields, Madeline C et al.·The Journal of rheumatology·2005

This study looked at how the hearts of fibromyalgia patients respond to position changes (lying down versus standing up) compared to people with other conditions including ME/CFS. Researchers used a specialized test that measures heart rate patterns during a tilt test and analyzed the data with advanced mathematical methods. They found no single heart response pattern that was unique to fibromyalgia, suggesting that fibromyalgia patients have different types of heart responses rather than one shared pattern.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCross-Sectional

Patterns of cardiovascular reactivity in disease diagnosis.

Naschitz, J E, Rosner, I, Rozenbaum, M et al.·QJM : monthly journal of the Association of Physicians·2004

This study looked at how the heart and blood vessels respond to changes in body position (lying down versus standing up) in people with ME/CFS compared to healthy people and those with other conditions. Researchers used a simple test where patients lie down and then tilt upright while measuring heart rate and blood vessel changes. They found that people with ME/CFS have a distinctive pattern of heart and blood vessel responses that could help doctors identify the condition.

Autonomic Nervous System

E2 ModerateCohortPEM unclearCase-Control

Peripheral cholinergic function in humans with chronic fatigue syndrome, Gulf War syndrome and with illness following organophosphate exposure.

Khan, Faisel, Kennedy, Gwen, Spence, Vance A et al.·Clinical science (London, England : 1979)·2004

Researchers tested how blood vessels in the forearm respond to acetylcholine (a chemical messenger in the body) in people with ME/CFS, Gulf War illness, and pesticide exposure. They found that people with ME/CFS had an unusually strong vascular response to acetylcholine, but people with the other two conditions had normal responses. This suggests ME/CFS may involve a specific problem with how the body breaks down acetylcholine in blood vessels.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCross-Sectional

Use of time-frequency analysis to investigate temporal patterns of cardiac autonomic response during head-up tilt in chronic fatigue syndrome.

Yoshiuchi, Kazuhiro, Quigley, Karen S, Ohashi, Kyoko et al.·Autonomic neuroscience : basic & clinical·2004

This study looked at how the nervous system that controls heart rate and blood pressure responds when people stand up from lying down. Researchers tested people with ME/CFS (with and without a condition called POTS), and compared them to healthy volunteers. They found that even ME/CFS patients without POTS showed subtle differences in how their heart rate changed during the standing test, suggesting their autonomic nervous system may not work quite normally.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCross-Sectional

Electrodermal dissociation of chronic fatigue and depression: evidence for distinct physiological mechanisms.

Pazderka-Robinson, Hannah, Morrison, James W, Flor-Henry, Pierre·International journal of psychophysiology : official journal of the International Organization of Psychophysiology·2004

This study looked at how the bodies of people with ME/CFS and people with depression respond differently to their surroundings. Researchers measured skin conductance (how easily electricity travels across the skin) and skin temperature while participants performed a task. They found that people with ME/CFS had notably lower skin conductance levels and higher skin temperature compared to people with depression and healthy controls, suggesting these are two different conditions with different underlying biology.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCross-Sectional

Assessment of cardiovascular reactivity by fractal and recurrence quantification analysis of heart rate and pulse transit time.

Naschitz, J E, Rosner, I, Shaviv, N et al.·Journal of human hypertension·2003

Researchers tested how the hearts of people with ME/CFS respond to a simple physical challenge (tilting from lying down to sitting up). They measured heart rate and blood vessel responses using advanced mathematical analysis that detects patterns typically missed by standard methods. People with ME/CFS showed very different heart responses compared to healthy people and those with high blood pressure, suggesting their cardiovascular systems react abnormally to physical stress.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCase-Control

Prolonged acetylcholine-induced vasodilatation in the peripheral microcirculation of patients with chronic fatigue syndrome.

Khan, Faisel, Spence, Vance, Kennedy, Gwen et al.·Clinical physiology and functional imaging·2003

This study looked at how blood vessels in the skin of ME/CFS patients respond to acetylcholine, a chemical messenger in the body. Researchers found that while the initial response was similar in patients and healthy controls, the blood vessels of ME/CFS patients took much longer to return to normal after the chemical was applied. This suggests that the way nerve signals control blood vessel function may be different in ME/CFS.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCross-Sectional

A measure of heart rate variability is sensitive to orthostatic challenge in women with chronic fatigue syndrome.

Yamamoto, Yoshiharu, LaManca, John J, Natelson, Benjamin H·Experimental biology and medicine (Maywood, N.J.)·2003

This study tested whether a simple heart rhythm measurement during a tilt test could help diagnose ME/CFS. Researchers compared heart rate patterns in 24 women with ME/CFS and 22 healthy women while they lay down and then tilted upright for 10 minutes. They found that women with ME/CFS showed a distinctive abnormal change in their heart rhythm pattern during tilting that could identify about 9 out of 10 ME/CFS patients correctly.

Autonomic Nervous System

← Previous Next 20 studies →

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.