ME/CFS Evidence Browser — Classified Studies on Myalgic Encephalomyelitis

961–980 of 6,157 studies

Acyclovir treatment of the chronic fatigue syndrome. Lack of efficacy in a placebo-controlled trial.

Straus, S E, Dale, J K, Tobi, M et al.·The New England journal of medicine·1988

Researchers tested whether acyclovir, an antiviral drug, could help people with ME/CFS who had signs of past Epstein-Barr virus infection. In this carefully controlled study of 27 patients, about half received the real drug and half received a placebo (fake treatment). After 37 days of treatment, similar numbers of people felt better in both groups—suggesting the drug itself wasn't the reason for improvement.

E2 ModerateCohortPEM requiredCross-Sectional

Distinct functional connectivity patterns in myalgic encephalomyelitis and long COVID patients during cognitive fatigue: a 7 Tesla task-fMRI study.

Inderyas, Maira, Thapaliya, Kiran, Marshall-Gradisnik, Sonya et al.·Journal of translational medicine·2026

This study used advanced brain imaging to compare how the brains of ME/CFS patients, long COVID patients, and healthy people work during a challenging thinking task. Researchers found that patients' brains show different patterns of communication between regions compared to healthy controls, particularly in areas related to motivation, memory, and emotional processing. These brain differences appeared to worsen as fatigue built up during the task.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearLongitudinal

Chronic Reactivation of Persistent Human Herpesviruses EBV, HHV-6 and VZV and Heightened Anti-dUTPase IgG Antibodies Are a Recurrent Hallmark in Post-Infectious ME/CFS and is Associated With Fatigue.

Palomo, Irene Mena, Cox, Brandon, Williams, Marshall V et al.·Journal of medical virology·2026

This study found that people with ME/CFS have higher levels of immune responses to three common viruses (EBV, HHV-6, and VZV) compared to healthy people. About 72% of ME/CFS patients showed antibodies to multiple viruses at the same time, versus only 31% of healthy controls. The antibody levels were higher in patients with moderate to severe fatigue, suggesting a possible connection between these viral reactivations and symptom severity.

BiomarkersImmune System

E2 ModerateCohortPEM unclearCross-Sectional

Understanding concussion in myalgic encephalomyelitis/chronic fatigue syndrome: Findings from the 2023 National Health Interview study.

Sirotiak, Zoe, Adamowicz, Jenna L, Thomas, Emily B K·Brain injury·2026

This study found that people with ME/CFS are nearly 5 times more likely to have had a concussion in the past year compared to people without ME/CFS. People with ME/CFS also experienced more falls and dizziness or balance problems. The researchers suggest that doctors should screen patients with ME/CFS more carefully for concussions and take steps to reduce their concussion risk.

Autonomic Nervous System

E2 ModerateBehavioralPEM not requiredObservational

Obesity and inactivity cluster the strongest risk factor for the development of heart failure in a population-based study.

van Essen, Bart J, Dan, Nathalie Ang En, Tharsana, Ganash N et al.·International journal of cardiology·2026

This study found that people with a combination of obesity and physical inactivity have the highest risk of developing heart failure compared to other groups with different health problems. Researchers followed nearly 7,000 people for about 10 years and identified six distinct groups based on their health conditions, discovering that the obesity and inactivity group had almost 4 times higher risk of heart failure than the healthiest group.

E2 ModerateBehavioralPEM not requiredCross-Sectional

Disentangling comorbidity: symptom dimensions of internalizing and functional disorders in a large general population sample.

Saini, Urvi, Aggen, Steven H, Oldehinkel, Albertine J et al.·BMC psychiatry·2026

This study looked at how symptoms of depression, anxiety, ME/CFS, fibromyalgia, and irritable bowel syndrome overlap in over 100,000 people. Researchers found that these conditions share common symptoms like fatigue, sleep problems, and difficulty concentrating—which they call 'general malaise'—rather than being completely separate diseases. Understanding these shared symptoms may help explain why people often have multiple conditions at the same time.

Pain and SensitizationCognitive Impairment

E2 ModerateCohortPEM unclearLongitudinal

Validation of the Wood Mental Fatigue Inventory in adolescents with myalgic encephalomyelitis/chronic fatigue syndrome.

Welch, David C, Edwards, Charles C, Broussard, Camille A et al.·Brain, behavior, & immunity - health·2026

This study tested whether a questionnaire called the Wood Mental Fatigue Inventory (WMFI) works well for measuring brain fog and cognitive problems in teenagers with ME/CFS. Researchers compared it to another commonly used teen fatigue scale and found that both questionnaires measured mental fatigue similarly and could track changes over time as teenagers received treatment.

Cognitive Impairment

E2 ModerateCohortPEM unclearCross-Sectional

Chronic Pain Prevalence, Characteristics, and Impact in United States Adults With Chronic Fatigue Syndrome/Myalgic Encephalomyelitis.

Adamowicz, Jenna L, Sirotiak, Zoe, Lendvai, Dora et al.·Pain management nursing : official journal of the American Society of Pain Management Nurses·2026

This study looked at how common chronic pain is in people with ME/CFS and how it affects their lives. Researchers found that about 7 out of 10 people with ME/CFS also experience chronic pain lasting months or longer. People with both ME/CFS and chronic pain reported more depression, anxiety, and difficulty with daily activities compared to people who only have chronic pain.

Pain and Sensitization

E2 ModerateCohortPEM not requiredCross-Sectional

Ocular Symptoms in Long COVID: A Cross-Sectional Study.

Kaleem, Shayaan, Sawano, Mitsuaki, Arun, Adith S et al.·Clinical ophthalmology (Auckland, N.Z.)·2026

This study looked at eye problems in people with long COVID, comparing those who developed new eye symptoms (like blurred vision, dry eyes, or floaters) after infection with those who didn't. About 57% of the 595 participants reported new eye symptoms. People with eye symptoms had worse overall health, more financial struggles, and were more likely to have dysautonomia (problems with blood pressure and heart rate control) and ME/CFS.

Autonomic Nervous System

E2 ModerateCohortPEM unclearCross-Sectional

Charting the circulating proteome in ME/CFS using cross-system profiling to uncover mechanistic insights.

Hoel, August, Hoel, Fredrik, Dyrstad, Sissel Elisabeth et al.·Cell reports. Medicine·2026

Researchers analyzed thousands of proteins in the blood of ME/CFS patients and compared them to healthy people. They found significant differences in protein patterns, including too much of certain immune-related proteins and too little of proteins normally made by muscles. These differences might help explain why ME/CFS causes such severe exhaustion and could eventually lead to new ways to diagnose or treat the condition.

BiomarkersImmune System

E2 ModerateCohortPEM unclearCase-Control

Urinary Peptidomic Profiling In Post-Acute Sequelae of SARS-CoV-2 Infection: A Case-Control Study.

Gülmez, Dilara, Siwy, Justyna, Kurz, Katharina et al.·Proteomics·2026

Researchers found a simple urine test that can accurately identify people with long COVID (PASC) by measuring tiny protein fragments in the urine. The test correctly identified long COVID patients 96% of the time compared to healthy people and those with ME/CFS. The urine signatures suggest that long COVID involves ongoing inflammation and changes in how the body breaks down and rebuilds connective tissue.

BiomarkersImmune System

E2 ModerateCohortPEM not requiredCross-Sectional

Long COVID disability burden in US adults.

Bonuck, Karen, Gao, Qi, Congdon, Seth et al.·Communications medicine·2026

This study measured how much disability Long COVID causes in American adults and compared it to other diseases like Alzheimer's and asthma. The researchers found that Long COVID causes as much disability as these well-known conditions, yet the U.S. government funds research on Long COVID with only 14% of the money it should based on that disability burden. The study also found that diseases affecting mostly women receive about 5 times less research funding per unit of disability than diseases affecting mostly men.

E2 ModerateCohortPEM requiredObservational

Assessment and Incidence Determination of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Following a SARS-CoV-2 Infection in a Prospective Cohort of Hospital Employees.

Tack, Matthias, Gruber, Rosalie, Betting, Leia et al.·Medicina (Kaunas, Lithuania)·2026

This study followed hospital workers who got COVID-19 to see how many developed long-lasting fatigue and ME/CFS. About 12% still had fatigue months later, and 3% met the criteria for ME/CFS. Researchers found that people with these conditions often had signs of viral reactivation, immune system changes, and blood clotting abnormalities.

Post-Exertional Malaise

E2 ModerateDiagnosticPEM unclearCross-Sectional

Improving myalgic encephalomyelitis population sampling: Applying an online respondent-driven method to address biases in G93.3 register data.

Kielland, Anne, Liu, Jing, Tyldum, Guri et al.·Journal of health psychology·2026

This study looked at how well official medical records capture ME/CFS cases and who gets diagnosed. Researchers found that medical register data misses many cases and disproportionately underrepresents people from lower-income backgrounds. They used a new online method to find ME/CFS patients more accurately and checked whether official diagnoses matched recognized diagnostic criteria.

Diagnostics

E2 ModerateCohortPEM requiredObservational

Postexertional Symptom Exacerbation after Submaximal Exercise in Individuals with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Postacute Sequelae of COVID-19.

Berardi, Giovanni, Janowski, Adam, McNally, Samuel et al.·Medicine and science in sports and exercise·2026

This study looked at what happens when people with ME/CFS or long COVID do moderate exercise. Researchers asked 60 patients and 30 healthy people to exercise for 25 minutes, then tracked their symptoms for a week. Most patients with ME/CFS experienced worsening fatigue, mental fog, and other symptoms in the days after exercise, but the severity and which symptoms got worse varied from person to person.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearCross-Sectional

Assessment of dynamic cerebral blood flow changes during cognitive tasks in patients with post-COVID-19 syndrome.

Kutz, Dieter F, Garbsch, René, Mooren, Frank C et al.·Brain communications·2026

This study looked at how blood flow in the brain changes when people with post-COVID-19 syndrome try to do mental tasks. Researchers used special infrared cameras to watch blood flow in the thinking part of the brain while patients did concentration exercises. They found that people with post-COVID-19 had unusual, less flexible blood flow patterns compared to healthy people, which may help explain why they feel mentally tired and have trouble concentrating.

Cognitive Impairment

E2 ModerateCohortPEM unclearCross-Sectional

Hypermethylation of OPRM1: Deregulation of the Endogenous Opioid Pathway in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Fibromyalgia.

Wyns, Arne, Hendrix, Jolien, Van Campenhout, Jente et al.·International journal of molecular sciences·2026

This study examined whether changes in how a gene called OPRM1 (which controls opioid receptors in the body) are chemically marked in people with ME/CFS and fibromyalgia. Researchers found that people with these conditions had higher levels of these chemical marks on the OPRM1 gene compared to healthy people, even after accounting for how severe their symptoms were. This suggests that problems with the body's natural pain-relief system may be a fundamental part of these illnesses.

E2 ModerateCohortPEM unclearObservational

Associations between heart rate and physical activity in people with post-COVID-19 condition accounting for myalgic encephalomyelitis/chronic fatigue syndrome symptoms.

Adodo, Rachel, Sarmento Da Nobrega, Antonio, Villar, Rodrigo et al.·Journal of rehabilitation medicine·2026

This study looked at how heart rate and physical activity are related in people with long COVID who also have ME/CFS-like symptoms. Researchers found that people experienced more episodes of rapid heartbeat (over 100 beats per minute) when they were resting or doing very little, but surprisingly had fewer of these episodes during moderate-to-vigorous exercise. This suggests that the relationship between activity and heart rate in long COVID may be more complex than previously thought.

Post-Exertional Malaise

E2 ModerateCohortPEM requiredLongitudinal

Post-discharge sequelae of Lassa fever survivors in Nigeria: an analysis of the LASCOPE prospective cohort.

Guichard, Eva, Juchet, Sylvain, Etafo, Ijeoma Chukwudumebi et al.·The Lancet. Infectious diseases·2026

This study followed 882 people who recovered from Lassa fever (a serious viral infection) after hospital discharge to see what long-term symptoms they experienced. Most survivors felt better within about 3 weeks after leaving the hospital, with the most common lingering symptoms being tiredness, headaches, and difficulty with physical activity. The good news is that serious complications like hearing loss were rare, affecting only 2% of survivors.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearCase-Control

ICD-10 Diagnoses prior to ME/CFS diagnosis in children and young people suggest potential early diagnostic indicators.

Wirth, Marielle, Haastert, Burkhard, Linnenkamp, Ute et al.·Scientific reports·2026

This study looked at medical records of young people (ages 6-27) diagnosed with ME/CFS to see what health problems they had in the year before their diagnosis. Researchers found that certain conditions—like fatigue, depression, pain disorders, and post-COVID-19 condition—appeared more often in people who later developed ME/CFS compared to similar young people who didn't develop it. This suggests these earlier diagnoses might be early warning signs or related to ME/CFS development, though the study cannot prove they actually caused ME/CFS.

Diagnostics

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Acyclovir treatment of the chronic fatigue syndrome. Lack of efficacy in a placebo-controlled trial.

Distinct functional connectivity patterns in myalgic encephalomyelitis and long COVID patients during cognitive fatigue: a 7 Tesla task-fMRI study.

Chronic Reactivation of Persistent Human Herpesviruses EBV, HHV-6 and VZV and Heightened Anti-dUTPase IgG Antibodies Are a Recurrent Hallmark in Post-Infectious ME/CFS and is Associated With Fatigue.

Understanding concussion in myalgic encephalomyelitis/chronic fatigue syndrome: Findings from the 2023 National Health Interview study.

Obesity and inactivity cluster the strongest risk factor for the development of heart failure in a population-based study.

Disentangling comorbidity: symptom dimensions of internalizing and functional disorders in a large general population sample.

Validation of the Wood Mental Fatigue Inventory in adolescents with myalgic encephalomyelitis/chronic fatigue syndrome.

Chronic Pain Prevalence, Characteristics, and Impact in United States Adults With Chronic Fatigue Syndrome/Myalgic Encephalomyelitis.

Ocular Symptoms in Long COVID: A Cross-Sectional Study.

Charting the circulating proteome in ME/CFS using cross-system profiling to uncover mechanistic insights.

Urinary Peptidomic Profiling In Post-Acute Sequelae of SARS-CoV-2 Infection: A Case-Control Study.

Long COVID disability burden in US adults.

Assessment and Incidence Determination of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Following a SARS-CoV-2 Infection in a Prospective Cohort of Hospital Employees.

Improving myalgic encephalomyelitis population sampling: Applying an online respondent-driven method to address biases in G93.3 register data.

Postexertional Symptom Exacerbation after Submaximal Exercise in Individuals with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Postacute Sequelae of COVID-19.

Assessment of dynamic cerebral blood flow changes during cognitive tasks in patients with post-COVID-19 syndrome.

Hypermethylation of OPRM1: Deregulation of the Endogenous Opioid Pathway in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Fibromyalgia.

Associations between heart rate and physical activity in people with post-COVID-19 condition accounting for myalgic encephalomyelitis/chronic fatigue syndrome symptoms.

Post-discharge sequelae of Lassa fever survivors in Nigeria: an analysis of the LASCOPE prospective cohort.

ICD-10 Diagnoses prior to ME/CFS diagnosis in children and young people suggest potential early diagnostic indicators.

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