ME/CFS Evidence Browser — Classified Studies on Myalgic Encephalomyelitis

1001–1020 of 6,157 studies

E2 ModerateCohortPEM not requiredObservational

Post-Exertional Malaise in Post-COVID-19 Syndrome: A Shift in the Frequency Across Pandemic Phases.

Ghali, Alaa, Lavigne, Christian, Ghali, Maria et al.·Journal of clinical medicine·2026

A French hospital study observed that post-COVID patients infected in 2020–2021 reported post-exertional malaise (PEM) more often than those infected later, and that PEM was associated with higher fatigue levels. By analogy, this may be relevant to ME/CFS patients, though the study examined post-COVID populations and the reasons for these differences remain uncertain—they could reflect changes in the virus, vaccination, immunity, or other unmeasured factors.

Long COVID OverlapPost-Exertional Malaise

E2 ModerateCohortPEM unclearCross-Sectional

3D Virtual Reality Performance Metrics as a Future Fatigue Biomarker in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).

Ladek, Anja-Maria, Priebe, Leonie, Harrer, Thomas et al.·Biomedicines·2026

Researchers tested how quickly 60 ME/CFS patients and 60 healthy controls could react to visual tasks presented in 3D virtual reality. ME/CFS patients showed slower reaction times across all difficulty levels, and they improved less with practice than controls did. The study reports an association between ME/CFS and prolonged reaction times, though the findings are preliminary and whether this could become a reliable test for fatigue severity requires further validation.

BiomarkersDiagnosticsCognitive Impairment

E2 ModerateCohortPEM unclearCross-Sectional

Elevated serum levels of interleukin-11 and matrix metalloproteinase-9 in myalgic encephalomyelitis/chronic fatigue syndrome.

Chinnappan, Baskaran, Kempuraj, Duraisamy, Aenlle, Kristina K et al.·Frontiers in immunology·2026

Researchers measured two immune proteins (IL-11 and MMP-9) in the blood of 40 ME/CFS patients and compared them to healthy controls, finding higher levels in the ME/CFS group. In the laboratory, they also showed that immune cells called mast cells release MMP-9 when exposed to a protein from Epstein-Barr virus. These are preliminary observations in one study that suggest these proteins may be associated with ME/CFS, but this does not yet establish their role in the disease.

NeuroinflammationBiomarkersImmune System

E2 ModerateBehavioralPEM not requiredObservational

The role of rehabilitation in Post-COVID-19 syndrome (PCS) recovery: An effectiveness study.

Collins, Gillian, Daly, Emma, Gallagher, David et al.·The British journal of occupational therapy·2026

This study tested whether a 6-week online rehabilitation program helped people recovering from long COVID. Thirty-six participants were tracked over 12 weeks—first during a waiting period where nothing changed, then during the rehabilitation program. The program, led by occupational therapists and physical therapists, taught practical strategies and provided peer support. Participants showed significant improvements in fatigue and symptom severity after completing the program.

E2 ModerateCohortPEM unclearCross-Sectional

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome diagnostic reporting in the 2021-2023 National Health Interview Survey.

Fleig, Katherine, Nahin, Richard, Stussman, Barbara et al.·BMC public health·2026

A survey of over 86,000 US adults found that approximately 1.5% reported ever receiving an ME/CFS diagnosis. Among those, about 21% reported they no longer have the condition (Past ME/CFS), though roughly 40–50% of this group still experience symptoms and functional limitations similar to those currently diagnosed. This study observed that people who report having recovered from ME/CFS remain more impaired than those who never had the diagnosis, suggesting that reported recovery does not necessarily mean full symptom resolution.

Diagnostics

E2 ModerateCohortPEM unclearObservational

Prediction of post-COVID chronic fatigue syndrome using data mining and machine learning techniques in Isfahan COVID cohort study.

Nematbakhsh, Shayan, Mohammadifard, Noushin, Riahi, Roya et al.·Journal of infection and public health·2026

Researchers used machine learning to identify factors associated with post-COVID fatigue in a cohort of 3,850 patients in Isfahan, Iran. The analysis identified 37 factors linked to fatigue; anxiety, BMI, depression, irritability, and memory issues were among the strongest predictors. A machine learning model achieved 85% accuracy at identifying patients at risk, though these results are based on observed associations and have not yet been validated in independent populations.

Diagnostics

E2 ModerateBehavioralPEM not requiredCase-Control

Increased Disease Burden in Irritable Bowel Syndrome With Comorbid Conditions and Psychiatric Diagnoses in a Multinational European Cohort: Results From the DISCOvERIE Project.

Midenfjord, Irina, Khadija, Mahrukh, Sundelin, Elias et al.·United European gastroenterology journal·2026

This study looked at 607 patients with irritable bowel syndrome (IBS) across nine European centers to understand how other conditions—like anxiety, depression, fibromyalgia, and chronic fatigue syndrome—affect their symptoms and overall health. Patients who had IBS along with one or more of these comorbid conditions experienced more severe digestive symptoms, mood problems, and fatigue than those with IBS alone. The more comorbidities someone had, the worse their symptoms became.

Pain and Sensitization

E2 ModerateCohortPEM requiredCross-Sectional

Impact of post-exertional malaise frequency and fatigue in Long COVID patients on health-related quality of life.

Thölking, Theresa, Müller, Frank, Riester, Tim et al.·Health and quality of life outcomes·2026

This study surveyed German adults with Long COVID and post-exertional malaise (PEM) to understand how the frequency and severity of PEM relates to quality of life. Researchers found that people reporting more frequent and more severe PEM were associated with lower quality-of-life scores, even after accounting for age, sex, and employment status. These are preliminary findings from a single survey and do not establish that PEM causes poor quality of life, but rather that the two observations occurred together in this group.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearCase-Control

Interpreting hand grip strength in hospital employees with post-COVID syndrome compared to non-infected controls: a case-control study.

Tack, Matthias, Gruber, Rosalie, Betting, Leia et al.·Scientific reports·2026

This small study compared hand grip strength in 19 hospital workers with post-COVID syndrome (including 7 who met ME/CFS criteria) to 23 healthy controls. Researchers found that grip strength tended to be lower in the post-COVID group, particularly when tested a second time after a 60-minute break, which might suggest difficulty recovering after repeated effort. However, these are preliminary findings from a small group, and the authors note that grip strength alone is not reliable enough to diagnose post-COVID syndrome.

DiagnosticsPost-Exertional Malaise

E2 ModerateCohortPEM unclearCase-Control

Sleep in myalgic encephalomyelitis/chronic fatigue syndrome shows marked night-to-night fluctuation under free-living conditions-results from a matched case-control study.

Saurel, Maïtena, Fornasieri, Isabelle, Del Sordo, Giovanna C et al.·Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine·2026

This study observed that people with ME/CFS who wore sleep-tracking wristbands for a week showed poorer sleep quality and more night-to-night variability in how well they slept compared to matched controls—even though they spent more time in bed. The sleep pattern was unstable from night to night, which may be an important feature of ME/CFS sleep problems that laboratory studies (typically 1–2 nights) do not capture.

SleepDiagnostics

E2 ModerateCohortPEM unclearLongitudinal

Post-Acute Sequelae of COVID-19 Persist Over 3 Years in Acute Lung Injury/Acute Respiratory Distress Syndrome Survivors But Are Not Associated With Persistent Thromboinflammation or Endothelial Dysfunction.

Jones, Ansley E, Khan, Zain, McGroder, Claire F et al.·Critical care explorations·2026

This study followed people who were hospitalized with severe COVID-19 for 3 years after they left the hospital. About one-quarter of them continued to experience long COVID symptoms like fatigue, brain fog, and difficulty with physical activity. Surprisingly, when researchers measured inflammation and blood vessel markers in their blood, these markers were not elevated and did not explain why some people had ongoing symptoms.

BiomarkersImmune SystemPost-Exertional Malaise

E2 ModerateCohortPEM unclearCross-Sectional

Cardiopulmonary Exercise Testing Reveals Functional Limitations and Work Disability in Severe Post-COVID-19 and ME/CFS Patients.

Tomaskovic, Aleksandar, Weber, Vincent, Ochmann, David T et al.·Sports medicine - open·2026

A cross-sectional study of 92 severely ill post-COVID patients found that those meeting ME/CFS criteria had lower measured aerobic capacity (oxygen uptake and power output) on exercise testing compared to post-COVID patients without ME/CFS. Two-thirds of all patients showed objective signs of work disability on testing, and these measurements correlated with patients' own reports of disability and their employment status. The relevance of these findings specifically to ME/CFS requires caution, as the study enrolled primarily post-COVID patients, and the overlap between these conditions remains incompletely understood.

Severe MEDiagnosticsLong COVID OverlapPost-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Associated factors and assessment of clinical symptoms including fatigue, insomnia, and gastrointestinal discomfort of chronic fatigue syndrome: a cross-sectional case-control study.

Xie, Fangfang, You, Yanli, Ma, Jianwen et al.·Journal of translational medicine·2026

This study compared 956 people with ME/CFS to 865 healthy people to understand what factors might contribute to the illness. Researchers measured fatigue, sleep problems, and digestive discomfort using standard questionnaires. They found that people with ME/CFS experienced all types of fatigue at roughly twice the severity of healthy controls, and that sleep and digestive problems often occurred together with ME/CFS.

Sleep

E2 ModerateCohortPEM unclearCase-Control

Phosphoproteomic analysis reveals differential associations between liver-spleen disharmony and qi-blood deficiency syndromes in chronic fatigue syndrome.

Zhang, Jiabao, Tian, Ying, Sun, Guanghan et al.·Journal of translational medicine·2026

Researchers compared blood protein markers in 30 people—10 with ME/CFS showing Traditional Chinese Medicine (TCM) 'Liver-Spleen Disharmony' patterns, 10 with 'Qi-Blood Deficiency' patterns, and 10 healthy controls—using advanced protein analysis. They observed different patterns of phosphorylated proteins (chemical modifications on proteins) between the two ME/CFS groups and healthy controls, suggesting that TCM pattern categories may have distinct molecular signatures. However, this is an early exploratory study with a small sample size, and these findings have not yet been replicated.

BiomarkersDiagnostics

E2 ModerateCohortPEM unclearObservational

Facility-Measured Sleep Electroencephalographic Microstructures in Long COVID.

Sun, Haoqi, Dang, Rammy, Li, Peng et al.·Sleep·2026

Researchers used overnight brain-wave recordings (EEG) to examine sleep patterns in people with long COVID and ME/CFS, comparing them to healthy controls. They found that both groups showed altered patterns in specific brain-wave features during sleep—such as changes in slow waves and sleep spindles (brief bursts of brain activity)—that may be associated with the unrefreshing sleep and fatigue these patients report. However, this is one study in a specific research setting, and it remains unclear whether these brain-wave changes are a cause of the symptoms or simply occur alongside them.

BiomarkersSleepLong COVID Overlap

E2 ModerateCohortPEM unclearObservational

Testing a Personalised Dysautonomia Management Protocol in Patients with Orthostatic Intolerance and a Diagnosis of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome or Long COVID.

Barr, Julia, Marsden, Lowri, Dassanayake, Theshan et al.·Journal of clinical medicine·2026

This observational study tested whether a personalised 8-week management plan (involving increased fluid and salt intake, pacing strategies, and calf exercises) was feasible and associated with symptom changes in 22 people with ME/CFS or Long COVID who experienced orthostatic intolerance. Reported improvements were modest: autonomic symptom scores improved by 7.7 points, and heart rate response during a standing test decreased slightly; however, adherence was highly variable, and the authors note that statistical improvements may not reflect clinically meaningful symptom relief. The study remains preliminary and cannot establish whether this protocol is an effective treatment.

InterventionsAutonomic Nervous System

E2 ModerateCohortPEM unclearCross-Sectional

Plasma Extracellular Vesicle Surface Marker Profiling Reveals Immune Cell-Associated Mitochondrial Membrane Potential Alterations in Long COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.

Ikeda, Gentaro, Koike-Ieki, Mariko, Inoue, Hiroyuki et al.·Open forum infectious diseases·2026

Researchers analyzed tiny cell particles called extracellular vesicles in blood samples from people with Long COVID, ME/CFS, and healthy controls. They observed that both Long COVID and ME/CFS groups had elevated levels of certain immune cell-derived particles and alterations in mitochondrial (energy-producing) markers within B cells and other immune cells, though the findings were not identical between groups. These preliminary results suggest there may be shared immune and metabolic changes in these conditions, but the meaning of these changes for patient health remains unclear and needs further study.

BiomarkersEnergy MetabolismImmune SystemLong COVID Overlap

E2 ModerateCohortPEM not requiredLongitudinal

Long COVID longitudinal symptoms burden clusters within a national community-based cohort.

Shen, Yanhan, Shahn, Zach, Robertson, McKaylee M et al.·BMC infectious diseases·2026

This study followed over 500 people with long COVID for up to a year, tracking their symptoms over time. Researchers identified three groups based on symptom burden: one with persistent severe symptoms (including fatigue, brain fog, post-exertional malaise, and pain), one with moderate symptoms that improved, and one with minimal symptoms. The findings are preliminary and based on self-reported data, so the stability and generalisability of these groups to other long COVID populations remain to be confirmed.

Pain and SensitizationSleepAutonomic Nervous SystemCognitive Impairment

E2 ModerateCohortPEM requiredCross-Sectional

Identifying post-exertional malaise subtypes: Differentiating physical and mental PEM manifestations.

Tuzzolino, Katherine, Jason, Leonard A, Furst, Jacob·Journal of health psychology·2026

This study looked at how post-exertional malaise (PEM)—the worsening of symptoms after activity—shows up differently in people with ME/CFS. Researchers divided patients into groups based on whether their PEM affected them physically (like muscle pain), mentally (like brain fog), both ways, or neither way severely. They found that people experiencing both physical and mental PEM had the worst overall symptoms, while those with neither type of severe PEM were less affected, though still much more disabled than healthy people.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredObservational

Shared genetic risk between functional somatic syndromes, internalizing disorders, and immune-mediated diseases: a twin-sibling study.

Steen, Olivier D, Ohlsson, Henrik, van Ockenburg, Sonja L et al.·Brain, behavior, and immunity·2026

A large Swedish study examined whether functional somatic syndromes (including ME/CFS, fibromyalgia, and IBS) and depression/anxiety share genetic risk factors with immune-mediated diseases. Researchers observed that fibromyalgia showed the strongest shared genetic risk with immune diseases, while ME/CFS showed more modest genetic overlap. The findings are preliminary and do not explain why these conditions cluster together, only that genetic factors may contribute to some shared risk.

BiomarkersImmune System

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Evidence browser

Post-Exertional Malaise in Post-COVID-19 Syndrome: A Shift in the Frequency Across Pandemic Phases.

3D Virtual Reality Performance Metrics as a Future Fatigue Biomarker in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).

Elevated serum levels of interleukin-11 and matrix metalloproteinase-9 in myalgic encephalomyelitis/chronic fatigue syndrome.

The role of rehabilitation in Post-COVID-19 syndrome (PCS) recovery: An effectiveness study.

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome diagnostic reporting in the 2021-2023 National Health Interview Survey.

Prediction of post-COVID chronic fatigue syndrome using data mining and machine learning techniques in Isfahan COVID cohort study.

Increased Disease Burden in Irritable Bowel Syndrome With Comorbid Conditions and Psychiatric Diagnoses in a Multinational European Cohort: Results From the DISCOvERIE Project.

Impact of post-exertional malaise frequency and fatigue in Long COVID patients on health-related quality of life.

Interpreting hand grip strength in hospital employees with post-COVID syndrome compared to non-infected controls: a case-control study.

Sleep in myalgic encephalomyelitis/chronic fatigue syndrome shows marked night-to-night fluctuation under free-living conditions-results from a matched case-control study.

Post-Acute Sequelae of COVID-19 Persist Over 3 Years in Acute Lung Injury/Acute Respiratory Distress Syndrome Survivors But Are Not Associated With Persistent Thromboinflammation or Endothelial Dysfunction.

Cardiopulmonary Exercise Testing Reveals Functional Limitations and Work Disability in Severe Post-COVID-19 and ME/CFS Patients.

Associated factors and assessment of clinical symptoms including fatigue, insomnia, and gastrointestinal discomfort of chronic fatigue syndrome: a cross-sectional case-control study.

Phosphoproteomic analysis reveals differential associations between liver-spleen disharmony and qi-blood deficiency syndromes in chronic fatigue syndrome.

Facility-Measured Sleep Electroencephalographic Microstructures in Long COVID.

Testing a Personalised Dysautonomia Management Protocol in Patients with Orthostatic Intolerance and a Diagnosis of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome or Long COVID.

Plasma Extracellular Vesicle Surface Marker Profiling Reveals Immune Cell-Associated Mitochondrial Membrane Potential Alterations in Long COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.

Long COVID longitudinal symptoms burden clusters within a national community-based cohort.

Identifying post-exertional malaise subtypes: Differentiating physical and mental PEM manifestations.

Shared genetic risk between functional somatic syndromes, internalizing disorders, and immune-mediated diseases: a twin-sibling study.

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