ME/CFS Evidence Browser — Classified Studies on Myalgic Encephalomyelitis

1021–1040 of 6,209 studies

E2 ModerateCohortPEM unclearCross-Sectional

Clinical Symptomatology, Cognition and Psychosocial Wellbeing in Adolescents With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Cross-Sectional Observational Study.

Chau, Tracey, Josev, Elisha K, Scheinberg, Adam et al.·Journal of paediatrics and child health·2026

This study compared 25 adolescents with mild-to-moderate ME/CFS to 25 healthy peers aged 10–19 years, finding that those with ME/CFS reported slower information processing, poorer sleep, lower quality of life, and higher anxiety and depression. Caregivers of adolescents with ME/CFS also reported concerns with attention and working memory. These are early findings from a small Australian sample, and it remains unclear how widely these observations apply to adolescents with ME/CFS in other settings or those with more severe illness.

SleepCognitive Impairment

E2 ModerateCohortPEM unclearCase-Control

Postural orthostatic tachycardia syndrome in adolescents with ME/CFS - a case control study.

Leone, Ariane, Gerrer, Katrin, Viereck, Anja et al.·Frontiers in pediatrics·2026

This study examined whether adolescents with ME/CFS have postural orthostatic tachycardia syndrome (PoTS), a condition where heart rate rises abnormally when standing up. Researchers compared 18 young people with ME/CFS to 18 healthy controls using interviews and a 10-minute standing test. PoTS was observed in 7 of the 18 ME/CFS patients but in none of the healthy controls. The study reports that a combination of symptom history and heart rate patterns during standing may help doctors diagnose PoTS in young people with ME/CFS, though the authors note further research is needed to confirm whether these findings apply more broadly.

Autonomic Nervous SystemDiagnostics

E2 ModerateCohortPEM requiredCross-Sectional

Total blood volume and red blood cell volume are not associated with orthostatic intolerance in adults with myalgic encephalomyelitis/chronic fatigue syndrome.

Yamazaki, Tadahiro, Mancini, Donna M, Blate, Michelle et al.·Physiological reports·2026

Researchers measured blood volume in 49 adults with ME/CFS and tested how their bodies responded to standing (using a lean test). They found that about half had abnormal responses to position changes, but these abnormalities were not clearly linked to whether participants had low, normal, or high blood volume. The findings suggest that other body systems—like nerve function or blood vessel control—may be more important than blood volume alone in explaining why many ME/CFS patients feel dizzy or unwell when standing.

BiomarkersAutonomic Nervous SystemDiagnostics

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

Construction and verification of an immune signature model for chronic fatigue syndrome: Leveraging TCM syndromes and elements for enhanced assessment.

Qin, Le-le, Zhang, Zhen-Xian, Wang, Jing-Han et al.·Journal of integrative medicine·2026

Researchers developed a scoring model combining blood test results (T-cell counts) and traditional Chinese medicine symptom patterns to predict which ME/CFS patients might have weakened immune function. In a study of 473 ME/CFS patients, the model identified 11 factors—including specific white blood cell counts, age, body weight, fatigue severity, sleep problems, and TCM symptom types—as associated with lower immune markers. The model performed reasonably well when tested on new patient data, though these are early findings and the model has not yet been validated in independent patient populations.

BiomarkersDiagnosticsImmune System

E2 ModerateCohortPEM unclearCross-Sectional

Overlapping Clinical Presentation of Long COVID and Postacute COVID-19 Vaccination Syndrome: Phenotypes, Severity, and Biomarkers.

Purpura, Lawrence, Heisler, Thomas, Palmer, Steven et al.·Clinical infectious diseases : an official publication of the Infectious Diseases Society of America·2026

This study compared three groups of people dealing with long-term effects from COVID-19: those with long COVID and ME/CFS, those with long COVID without ME/CFS, and those with symptoms after COVID-19 vaccination. While all three groups shared common symptoms like fatigue, the ME/CFS group experienced more widespread symptoms across their body. Interestingly, people in the vaccination-related group had higher rates of unusual symptoms like nerve pain and rashes, and their blood tests showed different patterns of autoimmune markers—substances that suggest the immune system may be attacking the body's own tissues.

Immune System

E2 ModerateCohortPEM unclearCase-Control

Microvascular remodeling and endothelial dysfunction across the post-COVID-19 spectrum: a prospective observational case-control study.

Wallraven, Timon, Günthner, Roman, Lethen, Isabelle et al.·BMC medicine·2026

Researchers studied blood vessel changes in the tiny vessels of the eye (using a technique called retinal vessel analysis) in people with post-COVID-19 syndrome and a subgroup meeting ME/CFS criteria, compared to people who recovered from COVID-19 and those never infected. People with post-COVID-19 syndrome, particularly those meeting ME/CFS criteria, showed narrower arteries and altered vessel patterns associated with worse symptoms and higher inflammation markers. While these findings are reported as preliminary observations, the relevance of post-COVID-19 vessel changes to ME/CFS specifically remains unclear, and this study does not yet establish whether such changes cause symptoms or could guide treatment.

BiomarkersDiagnosticsLong COVID Overlap

E2 ModerateCohortPEM unclearObservational

Haptoglobin Phenotypes Stratify Post-Exertional Cognitive Dysfunction Associated with Altered Cerebral Oxygenation and Metabolic Signatures in Long COVID.

Moezzi, Atefeh, Elremaly, Wesam, Leveau, Corinne et al.·International journal of molecular sciences·2026

This study observed that Long COVID patients with different versions of a protein called haptoglobin showed different patterns of cognitive problems after physical exertion. Patients carrying certain haptoglobin variants (Hp2) reported worse fatigue and cognitive decline following a challenge test, while those with the Hp1-1 variant showed better cognitive resilience. The findings are preliminary and come from a small group; larger studies are needed to confirm whether haptoglobin type could help identify which Long COVID patients are at higher risk for these cognitive changes.

BiomarkersEnergy MetabolismCognitive ImpairmentLong COVID Overlap

E2 ModerateCohortPEM unclearCross-Sectional

Identifying EEG biomarkers of fatigue and brain fog in long COVID: insights from rest and movement-related brain activity.

Casado Sánchez, M, Morales Fajardo, K, Long, S et al.·Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia·2026

A small study measured brain electrical activity in 20 people with long COVID who reported fatigue and brain fog, compared to 20 healthy controls. Researchers observed two types of altered brain patterns in the long COVID group: weaker electrical responses after hand movements and slower brain waves at rest in motor and sensory regions. These patterns were associated with cognitive symptoms and fatigue, but it remains unclear whether these brain changes explain the symptoms or are simply observed alongside them.

BiomarkersCognitive Impairment

E2 ModerateCohortPEM not requiredCross-Sectional

Factors Associated with Fibromyalgia Diagnosis amongst People Meeting Criteria: Results from UK Biobank.

Kim, Sung-A, Macfarlane, Gary J, Beasley, Marcus J·Arthritis care & research·2026

This study examined UK Biobank data to understand why many people who meet the clinical criteria for fibromyalgia do not receive a formal diagnosis from a doctor. Researchers found that about 73% of individuals meeting fibromyalgia criteria had not been diagnosed, and identified several factors associated with not receiving a diagnosis—including being male, being older, having shorter pain duration, and reporting less frequent fatigue. The findings suggest that diagnostic bias and stereotypical perceptions of fibromyalgia may delay or prevent people from getting a diagnosis, though this is one cross-sectional study and does not establish why these patterns occur.

Pain and SensitizationDiagnostics

E2 ModerateCohortPEM unclearObservational

Associated factors and a risk prediction model for comorbid circadian rhythm sleep-wake disorders in patients with chronic fatigue syndrome: implications for early screening and sleep health management.

Shao, Xiao, Yang, Fan, Qin, Le-le et al.·Frontiers in psychiatry·2026

This observational study of 610 ME/CFS patients found that roughly half also had circadian rhythm sleep-wake disorders (difficulty sleeping at normal times). The researchers identified several factors associated with this comorbidity, including female sex, higher fatigue severity, certain shift work patterns, and reduced deep sleep. They developed a prediction model to help identify patients at higher risk, though the study's retrospective design and unknown case definition quality mean these findings are preliminary and require validation in other patient populations.

Sleep

E2 ModerateCohortPEM unclearCross-Sectional

Microstructural alterations in brain tissue of ME/CFS and long COVID using diffusion tensor imaging and diffusion kurtosis imaging.

Singh, Tanoj Bahadur, Marshall-Gradisnik, Sonya, Barnden, Leighton et al.·Frontiers in medicine·2026

Researchers used specialized brain imaging scans (DTI and DKI) to observe differences in brain tissue structure between people with ME/CFS, people with long COVID, and healthy controls. They found that ME/CFS and long COVID showed microstructural changes in different brain regions, though the study is cross-sectional and cannot explain why these changes occur or what role they play in symptoms. These are preliminary findings that require replication in larger groups.

BiomarkersCognitive ImpairmentLong COVID Overlap

E2 ModerateCohortPEM unclearCase-Control

Circulating extracellular vesicles-microRNAs as potential biomarkers for the identification of ME/CFS: differentiating fatigue-related conditions.

Eguchi, Akiko, Kuratsune, Hirohiko, Nakatomi, Yasuhito et al.·Journal of translational medicine·2026

Researchers analysed tiny particles called extracellular vesicles in blood samples from patients with ME/CFS, chronic fatigue without a known cause, and depression, looking for differences in small RNA molecules that could help diagnose ME/CFS. They found a pattern of 114 different RNA molecules that appeared associated with ME/CFS and were rarely seen in healthy people, though these findings come from a small group of patients and have not yet been replicated in larger studies.

NeuroinflammationBiomarkersDiagnosticsLong COVID Overlap

E2 ModerateCohortPEM unclearCross-Sectional

Sex- and menopause-related differences in immune and gastrointestinal symptom architecture in ME/CFS: evidence from factor analysis and structural equation modeling.

Habermann-Horstmeier, Lotte, Horstmeier, Lukas M·Journal of translational medicine·2026

This study examined how immune and gut symptoms are organized differently in women and men with ME/CFS, and whether menopause affects these patterns. Researchers analyzed data from 748 people with ME/CFS and observed that women tend to have two somewhat separate symptom clusters (immune-related and gut-related), while men showed these symptoms more integrated together. Among women, flu-like symptoms were reported more frequently before menopause than after, while gut symptoms remained stable across menopause. These are early findings from a single cross-sectional analysis and require confirmation in future studies.

Endocrine DisruptionGut MicrobiomeAutonomic Nervous SystemImmune System

E2 ModerateCohortPEM unclearObservational

Wearable Heart Rate Variability Monitoring, Autonomic Dysfunction and Post-exertional Malaise in Long COVID: An Observational Study.

Ruijgt, Twan M, Slaghekke, Anouk, Ellens, Anneke et al.·Sports medicine (Auckland, N.Z.)·2026

This observational study measured heart rate variability (a marker of nerve system balance) in 121 long COVID patients and 21 healthy controls using wearable devices over multiple days. Researchers observed that long COVID patients had lower heart rate variability during daily activities and sleep, and their heart rate variability remained reduced for 24 hours after exercise, particularly at intensities above their aerobic threshold. The findings suggest wearables may help patients recognise when they are overexerting, though the study does not yet establish whether this monitoring prevents post-exertional malaise.

BiomarkersAutonomic Nervous SystemDiagnosticsPost-Exertional Malaise

E2 ModerateCohortPEM unclearCross-Sectional

Item comprehension and content coverage of patient-reported outcome measures for long COVID: a qualitative study.

Zigler, Christina K, Yousefian, Charis, Mangrum, Rikki et al.·Quality of life research : an international journal of quality of life aspects of treatment, care and rehabilitation·2026

Researchers asked 30 adults with Long COVID to review four existing survey questionnaires to see if the questions were clear and relevant to their condition. Participants reported they could understand most questions and found them relevant to their experiences. The study also identified ways these surveys could be improved, such as simplifying instructions and shortening length. These are preliminary findings from one qualitative study, and further testing of these surveys is planned.

Autonomic Nervous SystemDiagnosticsCognitive ImpairmentPost-Exertional Malaise

E2 ModerateCohortPEM unclearObservational

Perioperative outcomes in patients with myalgic encephalomyelitis/chronic fatigue syndrome undergoing general anesthesia: a retrospective matched-pair study.

Steinkirchner, Felix M, Kaufmann, Christina K, Kraus, Richard F et al.·BMC anesthesiology·2026

This small study compared 15 ME/CFS patients undergoing surgery with 15 matched controls to see how their bodies responded to anesthesia and surgery. Patients with ME/CFS showed lower blood pressure and heart rate during surgery, and experienced more pain afterward and needed more opioid medication; however, no serious complications occurred during anesthesia. The study was not designed to capture post-exertional malaise (symptom flare-ups after exertion), which is a central feature of ME/CFS and may occur after surgery.

Pain and SensitizationAutonomic Nervous System

E2 ModerateCohortPEM unclearCross-Sectional

Metabolomic Classification of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome via Explainable Ensemble Learning and Pareto-Guided Feature Selection.

Yagin, Fatma Hilal, Korkmaz, Yavuz, Colak, Cemil et al.·International journal of molecular sciences·2026

Researchers analysed blood metabolite patterns (small molecules in blood) from 106 people with ME/CFS and 91 healthy controls using machine learning to see whether these patterns could distinguish ME/CFS from health. A computer model called Explainable Boosting Machine achieved 91% accuracy in this one study group. Importantly, the findings remain preliminary—they describe associations observed in this cross-sectional sample and require external validation in new populations before clinical use.

BiomarkersEnergy MetabolismDiagnostics

E2 ModerateCohortPEM requiredObservational

Handgrip strength in children, adolescents, and young adults with suspected myalgic encephalomyelitis/chronic fatigue syndrome.

Mihatsch, Lorenz, Schartner, Lisa, de Luna, Julia Lange et al.·Journal of translational medicine·2026

Researchers tested whether handgrip strength could help identify ME/CFS in young people (ages 10–25). They asked 147 patients referred for ME/CFS assessment and 83 healthy controls to squeeze a hand-strength device twice, an hour apart. Young people with ME/CFS had weaker grip strength than healthy controls, and grip strength was loosely associated with physical functioning; however, grip strength alone could not reliably tell apart ME/CFS patients from other young people with chronic fatigue. The study shows that repeated handgrip testing is feasible and may help track how patients are doing over time, but early findings suggest it works better as a way to measure general weakness rather than as a standalone diagnostic test.

BiomarkersDiagnosticsPost-Exertional Malaise

E2 ModerateDiagnosticPEM unclearMethods-Paper

Agreement and reliability between the two-day 6-minute incremental step test and two-day cardiopulmonary exercise test in post COVID-19 condition for assessing post-exertional malaise: The REVEAL-study.

Bomans, Sarah, Michotte, Naomi, El M'Rabet, Imane et al.·PloS one·2026

Researchers compared two different exercise tests—one simpler and potentially more accessible (the 6-minute incremental step test) and one more complex (the cardiopulmonary exercise test)—to see if they could both measure post-exertional malaise in long COVID patients. In a small study of 25 people, the two tests did not measure the same outcomes equally well, though some measures like fatigue and effort perception showed moderate agreement. The simpler test may need further refinement before it can reliably replace the standard test.

DiagnosticsPost-Exertional Malaise

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Evidence browser

Clinical Symptomatology, Cognition and Psychosocial Wellbeing in Adolescents With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Cross-Sectional Observational Study.

Postural orthostatic tachycardia syndrome in adolescents with ME/CFS - a case control study.

Total blood volume and red blood cell volume are not associated with orthostatic intolerance in adults with myalgic encephalomyelitis/chronic fatigue syndrome.

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.

Construction and verification of an immune signature model for chronic fatigue syndrome: Leveraging TCM syndromes and elements for enhanced assessment.

Overlapping Clinical Presentation of Long COVID and Postacute COVID-19 Vaccination Syndrome: Phenotypes, Severity, and Biomarkers.

Microvascular remodeling and endothelial dysfunction across the post-COVID-19 spectrum: a prospective observational case-control study.

Haptoglobin Phenotypes Stratify Post-Exertional Cognitive Dysfunction Associated with Altered Cerebral Oxygenation and Metabolic Signatures in Long COVID.

Identifying EEG biomarkers of fatigue and brain fog in long COVID: insights from rest and movement-related brain activity.

Factors Associated with Fibromyalgia Diagnosis amongst People Meeting Criteria: Results from UK Biobank.

Associated factors and a risk prediction model for comorbid circadian rhythm sleep-wake disorders in patients with chronic fatigue syndrome: implications for early screening and sleep health management.

Microstructural alterations in brain tissue of ME/CFS and long COVID using diffusion tensor imaging and diffusion kurtosis imaging.

Circulating extracellular vesicles-microRNAs as potential biomarkers for the identification of ME/CFS: differentiating fatigue-related conditions.

Sex- and menopause-related differences in immune and gastrointestinal symptom architecture in ME/CFS: evidence from factor analysis and structural equation modeling.

Wearable Heart Rate Variability Monitoring, Autonomic Dysfunction and Post-exertional Malaise in Long COVID: An Observational Study.

Item comprehension and content coverage of patient-reported outcome measures for long COVID: a qualitative study.

Perioperative outcomes in patients with myalgic encephalomyelitis/chronic fatigue syndrome undergoing general anesthesia: a retrospective matched-pair study.

Metabolomic Classification of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome via Explainable Ensemble Learning and Pareto-Guided Feature Selection.

Handgrip strength in children, adolescents, and young adults with suspected myalgic encephalomyelitis/chronic fatigue syndrome.

Agreement and reliability between the two-day 6-minute incremental step test and two-day cardiopulmonary exercise test in post COVID-19 condition for assessing post-exertional malaise: The REVEAL-study.

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