ME/CFS Evidence Browser — Classified Studies on Myalgic Encephalomyelitis

21–40 of 73 studies

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 ModeratePEM unclearRegistry-Resource

Risk factors for severe post-COVID condition in children, adolescents, and young adults.

Donath, Quirin, Haegele, Matthias, Schindler, Daniela et al.·European journal of pediatrics·2026

This observational study from a German pediatric hospital followed 120 children and young adults with post-COVID condition (PCC), observing that those with more severe illness were more likely to have had 12 or more symptoms during their initial COVID-19 infection, alongside other acute symptoms such as trouble concentrating and fainting-like episodes. One quarter of participants met criteria for ME/CFS, and all of these were in the severely affected group; by analogy, if similar patterns apply to ME/CFS patients, early identification of high-symptom-burden acute illness might help predict who develops severe long-term illness. These findings are preliminary and come from a single hospital site.

Severe MEAutonomic Nervous SystemDiagnosticsCognitive Impairment

E2 ModerateCohortPEM unclearCross-Sectional

Central noradrenergic deficiency in post-infectious chronic fatigue: neurobehavioral correlates.

Aregawi, Lillian, Walitt, Brian, Sullivan, Patti et al.·Brain communications·2026

Researchers measured levels of norepinephrine (a brain chemical) in cerebrospinal fluid from people with ME/CFS, Long COVID, and Parkinson's disease, comparing them to healthy volunteers. They observed that norepinephrine pathway activity was lower in all three patient groups, and in Long COVID patients with post-exertional malaise, this reduction was particularly pronounced. This is one study in a small sample, and it remains unclear whether these findings fully explain fatigue and brain fog or apply directly to ME/CFS.

BiomarkersCognitive ImpairmentLong COVID OverlapPost-Exertional Malaise

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 unclearCross-Sectional

Symptom, Functional, and Work Participation Profiles Among Racialized Canadians with Pre-Existing Mental Health Challenges and Long COVID: A Cross-Sectional Study.

Shahzad, Maryam, Siddiqui, Sana, Lau, Chloe et al.·Healthcare (Basel, Switzerland)·2026

This study observed symptom burden, functional impairment, and mental health outcomes in 51 Canadian adults with long COVID who also identified as racialized and had pre-existing mental health conditions. Participants reported moderate overall symptoms, notable fatigue and post-exertional malaise, cognitive difficulties, and mild-to-moderate anxiety and depression, alongside moderate functional limitations in work, social, and daily activities. However, this is a small, self-selected group, and the findings may not generalise to all long COVID patients.

Cognitive ImpairmentLong COVID OverlapPost-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Subclinical Hypercoagulable Viscoelastic Characteristics Associated with Post-Acute Sequelae of SARS-CoV2 Physical Symptoms in COVID-19 ALI/ARDS Survivors.

Jones, Ansley E, Mira-Sanchez, Margarita, Khan, Zain et al.·Journal of intensive care medicine·2026

This study examined blood clotting patterns in 93 people who survived severe COVID-19 requiring hospitalization, testing them 15 months after discharge. Researchers observed that those with lingering post-COVID symptoms—particularly fatigue and post-exertional malaise (worsening after activity)—showed altered clotting characteristics on specialized blood tests, specifically higher fibrinogen levels. However, this is a single cross-sectional study and does not establish whether these clotting changes cause the symptoms or are simply associated with them.

BiomarkersLong COVID Overlap

E2 ModerateCohortPEM not requiredCross-Sectional

Persistent fatigue in long-COVID is not associated with peripheral inflammatory or cellular stress biomarkers: A cross-sectional controlled study.

Omdal, Roald, Lenning, Ole Bernt, Jonsson, Grete et al.·Brain, behavior, & immunity - health·2026

A study of 48 people with long-COVID and 48 recovered controls found that fatigue was much more severe in the long-COVID group, but common blood markers of inflammation and cellular stress did not differ between the groups. This suggests that the fatigue in long-COVID may not be driven by the types of inflammation typically measured in blood tests, though the researchers note their findings are preliminary and limited to the biomarkers they tested.

NeuroinflammationBiomarkersImmune SystemLong COVID Overlap

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 unclearCross-Sectional

FreeSurfer-based amygdala subfield volumetry in long COVID and ME/CFS: clinical and immunological correlations.

Kimura, Yukio, Sato, Wakiro, Shigemoto, Yoko et al.·Frontiers in neurology·2026

Researchers used high-resolution brain imaging to examine a small part of the brain called the amygdala in people with long COVID, ME/CFS, and healthy controls. They observed some differences in the size of specific amygdala regions between groups and found associations between these brain measurements and certain immune markers, but these findings were preliminary and did not remain significant after statistical correction for multiple comparisons. The study is exploratory and does not yet establish why these brain differences occur or whether they are clinically meaningful.

NeuroinflammationBiomarkersLong COVID Overlap

E2 ModerateCohortPEM unclearObservational

High Frequency of HHV-7 Reactivation in Neurological and Neuropsychiatric Long COVID: A Retrospective Observational Study.

Ducret, Diane, Mijatovic, Tatjana·Viruses·2026

A retrospective study observed that patients with neurological or neuropsychiatric symptoms after COVID-19 had a substantially higher frequency of HHV-7 (a type of herpesvirus) detected in testing compared to pre-COVID reference data. The study involved 30 long COVID patients, of whom 77% tested positive for HHV-7, compared to 29% in historical controls. The authors note that these are early findings in a small patient group and call for prospective studies to investigate whether HHV-7 plays a role in long COVID neurological symptoms.

NeuroinflammationBiomarkersLong COVID Overlap

E2 ModerateCohortPEM unclearCross-Sectional

Comparative Gut Microbiome Alterations in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Long COVID-19 Syndrome.

Donchev, Deyan, Nikolova, Ralitsa, Vaseva, Katya et al.·Biomedicines·2026

Researchers compared gut bacteria in people with ME/CFS, long COVID, and healthy controls using stool samples. They observed that both ME/CFS and long COVID showed similar patterns of bacterial changes—including more of a bacterium called Sutterella and less of others—compared to healthy people, though the two conditions were not identical. The strongest links between bacterial patterns and symptoms were observed in fatigue and physical symptoms, though this is one study and findings require confirmation in larger follow-up research.

BiomarkersGut MicrobiomeEnergy MetabolismLong COVID Overlap

E2 ModerateCohortPEM unclearCross-Sectional

Involvement of autoantibodies against G protein-coupled receptors in post-COVID condition and Chronic Fatigue Syndrome.

Azcue, N, Prada, A, Del Pino, R et al.·Scientific reports·2026

Researchers compared immune markers called autoantibodies in people with post-COVID condition, ME/CFS, and healthy controls. They found that people with ME/CFS had higher levels of antibodies against certain nerve receptors (β2 adrenergic), and these antibodies were associated with autonomic nervous system problems and memory changes. However, this is a single cross-sectional study, and autoimmunity remains one of several proposed mechanisms—it is not yet clear whether these antibodies are a cause or a consequence of ME/CFS.

BiomarkersAutonomic Nervous SystemImmune SystemCognitive Impairment

E2 ModerateCohortPEM unclearLongitudinal

Two-timepoint multidomain follow-up of post-COVID condition and ME/CFS: overlapping autonomic, small-fiber, and cognitive changes.

Azcue, N, Barranco, C, Tijero-Merino, B et al.·Journal of translational medicine·2026

Researchers compared 21 people with post-COVID condition and 17 people with ME/CFS over about 2.5 years, measuring nerve function, autonomic symptoms, and cognitive performance. They observed that both groups showed similar patterns of changes over time—including worsening processing speed and cold sensation sensitivity, but improving heat sensation thresholds and verbal memory. While the two conditions appeared increasingly alike on follow-up testing, the study does not establish whether they are truly the same disease or simply share overlapping symptoms.

Pain and SensitizationAutonomic Nervous SystemDiagnosticsCognitive Impairment

E2 ModerateCohortPEM unclearObservational

Exploratory clinical and immunological changes following Tixagevimab/Cilgavimab administration in immunodeficient patients with SARS-CoV-2-associated ME/CFS and persistent circulating spike protein.

Seidel, Maximilian, Anft, Moritz, Wiemers, Lea et al.·Immunology letters·2026

Researchers gave a monoclonal antibody treatment (Tixagevimab/Cilgavimab) to nine immunodeficient patients with long COVID and ME/CFS-like symptoms who had detectable coronavirus spike protein in their blood. After 30 days, one immune marker (β1-adrenergic receptor autoantibody) showed a modest decrease, but spike protein levels and symptom outcomes did not change significantly as a group. These are very preliminary findings from a small study without a control group, and the authors emphasise that efficacy remains uncertain.

BiomarkersInterventionsAutonomic Nervous SystemImmune System

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 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 unclearObservational

Elevated risk of new-onset chronic fatigue syndrome/myalgic encephalomyelitis up to four years after SARS-CoV-2 infection.

Hadidchi, Roham, Patel, Bhakti, Madan, Japji et al.·Journal of translational medicine·2025

This study found that people who had COVID-19 are more likely to develop ME/CFS in the years following infection compared to people who never had COVID-19. Women, and people with existing autoimmune or anxiety disorders, appear to be at higher risk. Importantly, having COVID-19 again did not increase the risk further, and blood tests during acute COVID were not able to predict who would later develop ME/CFS.

Long COVID Overlap

E2 ModerateCohortPEM not requiredCross-Sectional

Unmasking the Long-Term Effects of COVID-19 With a Focus on Chronic Fatigue Syndrome: A Community-Based Study From India.

Gupta, Arti, Rajan, Vishnu, Aravindakshan, Rajeev et al.·Cureus·2025

This study looked at 500 COVID-19 survivors in rural India to see how many developed chronic fatigue syndrome (CFS)—a condition causing severe, lasting tiredness and other symptoms. About 21% of the COVID-19 survivors developed CFS, with older people, women, and those with existing health conditions at higher risk. The study found that fatigue, joint pain, and muscle pain were common problems after COVID-19.

Long COVID Overlap

E2 ModerateCohortPEM unclearCross-Sectional

Cognitive Impairments in Two Samples of Individuals with ME/CFS and Long COVID: A Comparative Analysis.

Sirotiak, Zoe, Adamowicz, Jenna L, Thomas, Emily B K·Journal of clinical psychology in medical settings·2025

This study looked at brain fog and concentration problems in people with ME/CFS and long COVID using data from over 27,000 Americans. Researchers found that people with ME/CFS are about 6 times more likely to experience cognitive difficulties like memory and concentration problems compared to people without these conditions, while long COVID increases the risk about 2 times. People who have both ME/CFS and long COVID together face even greater cognitive challenges.

Long COVID Overlap

E2 ModerateCohortPEM unclearCross-Sectional

Comparable Immune Alterations and Inflammatory Signatures in ME/CFS and Long COVID.

Petrov, Steliyan, Bozhkova, Martina, Ivanovska, Mariya et al.·Biomedicines·2025

This study compared immune system markers in people with ME/CFS and Long COVID to those of healthy individuals. Both patient groups showed similar immune problems: lower levels of protective immune cells and higher levels of inflammatory substances in their blood. The findings suggest that ME/CFS and Long COVID may involve very similar underlying immune dysfunction.

Immune SystemLong COVID Overlap

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

Risk factors for severe post-COVID condition in children, adolescents, and young adults.

Central noradrenergic deficiency in post-infectious chronic fatigue: neurobehavioral correlates.

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

Symptom, Functional, and Work Participation Profiles Among Racialized Canadians with Pre-Existing Mental Health Challenges and Long COVID: A Cross-Sectional Study.

Subclinical Hypercoagulable Viscoelastic Characteristics Associated with Post-Acute Sequelae of SARS-CoV2 Physical Symptoms in COVID-19 ALI/ARDS Survivors.

Persistent fatigue in long-COVID is not associated with peripheral inflammatory or cellular stress biomarkers: A cross-sectional controlled study.

Facility-Measured Sleep Electroencephalographic Microstructures in Long COVID.

FreeSurfer-based amygdala subfield volumetry in long COVID and ME/CFS: clinical and immunological correlations.

High Frequency of HHV-7 Reactivation in Neurological and Neuropsychiatric Long COVID: A Retrospective Observational Study.

Comparative Gut Microbiome Alterations in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Long COVID-19 Syndrome.

Involvement of autoantibodies against G protein-coupled receptors in post-COVID condition and Chronic Fatigue Syndrome.

Two-timepoint multidomain follow-up of post-COVID condition and ME/CFS: overlapping autonomic, small-fiber, and cognitive changes.

Exploratory clinical and immunological changes following Tixagevimab/Cilgavimab administration in immunodeficient patients with SARS-CoV-2-associated ME/CFS and persistent circulating spike protein.

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

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

Elevated risk of new-onset chronic fatigue syndrome/myalgic encephalomyelitis up to four years after SARS-CoV-2 infection.

Unmasking the Long-Term Effects of COVID-19 With a Focus on Chronic Fatigue Syndrome: A Community-Based Study From India.

Cognitive Impairments in Two Samples of Individuals with ME/CFS and Long COVID: A Comparative Analysis.

Comparable Immune Alterations and Inflammatory Signatures in ME/CFS and Long COVID.

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