ME/CFS Evidence Browser — Classified Studies on Myalgic Encephalomyelitis

1061–1080 of 6,188 studies

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 requiredCross-Sectional

Examining Well-Being and Cognitive Function in People With Long COVID and ME/CFS, and Age-Matched Healthy Controls: A Case-Case-Control Study.

Sanal-Hayes, Nilihan E M, Mclaughlin, Marie, Hayes, Lawrence D et al.·The American journal of medicine·2025

This study compared how people with long COVID and ME/CFS experience their daily well-being and thinking abilities, compared to healthy people of similar ages. Researchers found that both long COVID and ME/CFS patients reported similar struggles with fatigue, pain, sleep problems, anxiety, and difficulty with everyday activities—but their actual test performance on thinking tasks was comparable to healthy controls. The findings suggest that both conditions affect quality of life in very similar ways.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearCase-Control

Steroid dynamics in myalgic encephalomyelitis / chronic fatigue syndrome: a case-control study using ultra performance supercritical fluid chromatography tandem mass spectrometry.

Thomas, Natalie, Ubhayasekera, S J Kumari A, Armstrong, Christopher W et al.·Journal of translational medicine·2025

This study looked at stress hormones (steroids) in the blood of people with ME/CFS compared to healthy controls. While the amounts of individual hormones were similar between the two groups, the researchers found that the hormones were not communicating with each other properly in ME/CFS patients—like instruments in an orchestra playing out of sync. This suggests that the body's hormone regulation system may be disrupted in ME/CFS, even when individual hormone levels appear normal.

E2 ModerateCohortPEM not requiredCross-Sectional

Deep learning analysis of long COVID and vaccine impact in low- and middle-income countries (LMICs): development of a risk calculator in a multicentric study.

Shaheen, Ahmed, Shaheen, Nour, Long COVID Collaboration Study Group in the LMICs et al.·Frontiers in public health·2025

Researchers studied over 2,400 COVID-19 patients in low- and middle-income countries to understand why some people develop long-lasting symptoms like chronic fatigue and depression after infection. They used advanced computer analysis to identify which patients were at highest risk for these prolonged symptoms. The study found that vaccination reduced the risk of developing these long-term problems, and that older age, being female, and smoking were linked to higher risk of chronic fatigue.

E2 ModerateBehavioralPEM not requiredCross-Sectional

Comparing autonomic nervous system function in patients with functional somatic syndromes, stress-related syndromes and healthy controls.

Van Den Houte, Maaike, Ramakers, Indra, Van Oudenhove, Lukas et al.·Journal of psychosomatic research·2025

This study measured how the nervous system responds to stress in people with ME/CFS and similar conditions, compared to healthy people. Researchers found that patients with ME/CFS and stress-related conditions had their 'stress response system' stuck in overdrive even at rest, and this system didn't properly calm down after stress passed. These findings suggest that autonomic nervous system dysfunction—an imbalance in the automatic systems that control heart rate and other vital functions—may be a common feature across these conditions.

Autonomic Nervous System

E2 ModerateCohortPEM unclearCross-Sectional

Assessing the Relationship in Symptomology of Myalgic Encephalitis/Chronic Fatigue Syndrome and Long COVID.

Garapaty, Nikitha, Reyes, Kristina M, Tehrani, Lily et al.·American journal of medicine open·2025

This study compared symptoms in people with ME/CFS, Long COVID, both conditions together, and people without either condition. Researchers found that people who have both ME/CFS and Long COVID experience the worst symptoms—including memory problems, anxiety, depression, fatigue, and difficulty exercising—compared to people with just one condition or neither. The findings suggest these two illnesses may interact in ways that make symptoms more severe when they occur together.

Cognitive Impairment

E2 ModerateCohortPEM unclearCross-Sectional

Poor Association Between Clinical Characteristics and Seropositivity in Children With Suspected Long COVID-A Single-Centre Study.

Olsson-Åkefeldt, S, Luthander, J, Anmyr, L et al.·Acta paediatrica (Oslo, Norway : 1992)·2025

This study looked at 113 children and teenagers who visited a specialized clinic for suspected long COVID symptoms. The researchers found that about half of the children had antibodies showing they had been infected with SARS-CoV-2, while the other half did not. Most children reported multiple symptoms like fatigue, dizziness, difficulty concentrating, and nausea, and these symptoms were similar whether or not they had evidence of past COVID infection. Many children were missing school and had to stop doing activities they enjoyed.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Assessment of the Gut Microbiome in Patients with Coexisting Irritable Bowel Syndrome and Chronic Fatigue Syndrome.

Chojnacki, Marcin, Błońska, Aleksandra, Kaczka, Aleksandra et al.·Nutrients·2025

This study looked at the gut bacteria and their byproducts in 80 women, comparing those with IBS alone to those with both IBS and chronic fatigue. Women with both conditions had different types of bacteria and different levels of certain chemicals in their urine, particularly those related to tryptophan (an amino acid). Higher levels of some of these chemicals were linked to worse fatigue symptoms.

Gut Microbiome

E2 ModerateCohortPEM requiredObservational

Post-exertional malaise in Long COVID: subjective reporting versus objective assessment.

Stussman, Barbara, Camarillo, Nathan, McCrossin, Gayle et al.·Frontiers in neurology·2025

This study looked at post-exertional malaise (PEM)—the symptom worsening that happens after activity—in people with Long COVID. Researchers asked patients about PEM symptoms and had some patients do an exercise test to see if PEM actually occurred. While 67% of patients reported having PEM symptoms, only 6% actually showed clear PEM after the exercise test. When PEM did occur in Long COVID, it was less severe than what the researchers saw in ME/CFS patients.

Severe MEPost-Exertional Malaise

E2 ModerateCohortPEM unclearLongitudinal

Long COVID-19: a Four-Year prospective cohort study of risk factors, recovery, and quality of life.

Kamal, Sanaa M, Al Qahtani, Mohammed S, Al Aseeri, Ali et al.·BMC infectious diseases·2025

This study followed 816 people in Saudi Arabia for up to four years after they had COVID-19 to see who developed long COVID and what symptoms they experienced. Researchers found that about 29% developed long COVID, with fatigue, post-exertional malaise (worsening after activity), cough, and brain fog being the most common symptoms. Women and people with diabetes were at higher risk, and those who got reinfected or were hospitalized took longer to recover.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearObservational

Autonomic Dysfunction in Patients with Acute Infection with Coxiella burnetii.

Milovanović, Branislav, Marković, Nikola, Ristanović, Elizabeta et al.·Pathogens (Basel, Switzerland)·2025

This study looked at how the autonomic nervous system (the part that controls heart rate, blood pressure, and other automatic body functions) works in people who had acute infection with Coxiella burnetii, a bacterium that causes Q fever. Researchers tested 100 infected patients and 56 healthy controls using heart monitoring tests and found that infected patients had more problems with autonomic control, particularly in how their bodies regulate heart rate and blood pressure. These findings suggest that this infection might trigger lasting problems with the autonomic nervous system that could contribute to ME/CFS symptoms.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCase-Control

No reduced serum serotonin levels in patients with post-acute sequelae of COVID-19.

Mathé, Philipp, Götz, Veronika, Stete, Katarina et al.·Infection·2025

Researchers compared serotonin levels in the blood of 34 people with long COVID (PASC) and 14 healthy people. Serotonin is a chemical in the body that affects mood and fatigue. The study found no meaningful difference in serotonin levels between the two groups, suggesting that low serotonin is probably not the main cause of long COVID symptoms.

Biomarkers

E2 ModerateCohortPEM unclearObservational

A comparison of genome-wide association analyses of persistent symptoms after Lyme disease, fibromyalgia, and myalgic encephalomyelitis - chronic fatigue syndrome.

Hirsch, Annemarie G, Justice, Anne E, Poissant, Amy et al.·BMC infectious diseases·2025

Researchers studied the genes of people who had Lyme disease to understand why some develop lasting symptoms even after treatment. They found two genetic regions that might be involved in persistent Lyme disease symptoms, with one linked to a protein called MARC2 that affects immune function. When they checked whether these same genetic changes appeared in people with fibromyalgia or ME/CFS, they did not find the same patterns, suggesting these conditions may have different genetic roots.

Immune System

E2 ModerateCohortPEM unclearCross-Sectional

Age-specific alterations of the gut mycobiome in patients with myalgic encephalomyelitis/chronic fatigue syndrome and identification of potential diagnostic biomarkers.

Gan, Yunong, Ning, Ruihong, Zhang, Wen et al.·BMC microbiology·2025

Researchers studied fungi living in the gut of ME/CFS patients compared to healthy people across different age groups. They found that people with ME/CFS have different types and amounts of gut fungi than healthy people, and these differences vary depending on age. Using these fungal patterns, they could identify ME/CFS patients with high accuracy—especially when looking at people of similar ages—suggesting gut fungi might help diagnose the condition.

Biomarkers

E2 ModerateCohortPEM unclearCross-Sectional

Long COVID in the population of COVID-19 hospitalized patients discharged from SUS' hospitals in Rio de Janeiro City, Brazil: a patient-engaged cohort survey study.

Portela, Margareth Crisóstomo, Lima, Sheyla Maria Lemos, Escosteguy, Claudia Caminha et al.·BMC infectious diseases·2025

This Brazilian study surveyed over 11,000 people who were hospitalized with COVID-19 to see how many experienced long-lasting symptoms months later. About 71% reported frequent ongoing symptoms like fatigue, brain fog, and joint pain, while 39% said they had Long COVID. The researchers found that women, people with previous health conditions, and certain age groups were more likely to experience these persistent symptoms.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

The Relationship Between Hemodynamic Responses During Head-Up Tilt Testing and Parameters of Infection in Post-COVID Syndrome, Chronic Fatigue Syndrome, and Late-Stage Lyme Disease.

Milovanovic, Branislav, Markovic, Nikola, Petrovic, Masa et al.·Viruses·2025

This study examined 1036 patients with post-COVID syndrome, chronic fatigue syndrome, and Lyme disease to understand why they experience dizziness and fainting when standing up. Researchers performed tilt-table tests (where patients lie on a table that tilts upward) and checked for signs of past or ongoing infections through blood tests. They found that patients with evidence of multiple past infections were more likely to have abnormal responses during the tilt test, suggesting that lingering effects from infections may affect the nervous system's ability to control blood pressure and heart rate.

Autonomic Nervous System

E2 ModerateCohortPEM not requiredCross-Sectional

Association between pre-existing chronic conditions and severity of first SARS-CoV-2 infection symptoms among adults living in Canada: a population-based survey analysis from January 2020 to August 2022.

Cheta, Nicholas, Zakaria, Dianne, Demers, Alain et al.·BMC public health·2025

This Canadian study looked at whether people with long-term health conditions experienced more severe COVID-19 symptoms when they caught the virus. Researchers surveyed over 10,000 adults from 2020 to 2022 and found that certain conditions—like chronic lung disease, high blood pressure, ME/CFS, fibromyalgia, and arthritis—were linked to worse COVID-19 symptoms. This information can help doctors identify who might need extra support or preventive care when facing a COVID-19 infection.

E2 ModerateCohortPEM not requiredCase-Control

In transfusion-dependent thalassemia, neuronal damage biomarkers are associated with affective and chronic fatigue symptoms.

Ridhaa, Maha Abdul Saheb, Al-Hakeim, Hussein Kadhem, Kahlol, Mohammed K et al.·Scientific reports·2025

This study looked at children with thalassemia, a blood disorder requiring frequent transfusions, to see if brain damage and inflammation might cause depression, anxiety, and chronic fatigue. Researchers measured specific markers of brain injury and inflammation in the blood and found that children with thalassemia had higher levels of these markers and more fatigue and mood symptoms than healthy children. The study suggests that iron buildup from transfusions may damage nerve cells in the brain, leading to these symptoms.

Neuroinflammation

E2 ModerateCohortPEM unclearCross-Sectional

Physical activity and sedentariness levels in patients with post-exertional malaise resulting from post-COVID-19 syndrome.

Elkebir, Kamel-Eddine, Gilbert, Jo-Anne, Kugathasan, Thiffya Arabi et al.·Work (Reading, Mass.)·2025

This study looked at how physical activity changed in 154 people who developed post-exertional malaise (PEM)—extreme tiredness and pain that worsens after activity—following COVID-19. Researchers found that after COVID-19, these patients became much less active and spent more time sitting, especially at work. Women and those with more severe PEM were most affected by these changes.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearLongitudinal

Health outcomes up to 3 years and post-exertional malaise in patients after hospitalization for COVID-19: a multicentre prospective cohort study (CO-FLOW).

Berentschot, Julia C, Bek, L Martine, Drost, Manon et al.·The Lancet regional health. Europe·2025

This study followed 299 people hospitalized with COVID-19 for three years after discharge to track their recovery. While some improved over time, many people continued experiencing fatigue, memory problems, and cognitive difficulties—and these problems actually got worse between years 2 and 3. About one-third of patients developed post-exertional malaise (PEM), a condition where activity makes symptoms significantly worse, and these patients had more severe and persistent health problems throughout the study.

Post-Exertional Malaise

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

Examining Well-Being and Cognitive Function in People With Long COVID and ME/CFS, and Age-Matched Healthy Controls: A Case-Case-Control Study.

Steroid dynamics in myalgic encephalomyelitis / chronic fatigue syndrome: a case-control study using ultra performance supercritical fluid chromatography tandem mass spectrometry.

Deep learning analysis of long COVID and vaccine impact in low- and middle-income countries (LMICs): development of a risk calculator in a multicentric study.

Comparing autonomic nervous system function in patients with functional somatic syndromes, stress-related syndromes and healthy controls.

Assessing the Relationship in Symptomology of Myalgic Encephalitis/Chronic Fatigue Syndrome and Long COVID.

Poor Association Between Clinical Characteristics and Seropositivity in Children With Suspected Long COVID-A Single-Centre Study.

Assessment of the Gut Microbiome in Patients with Coexisting Irritable Bowel Syndrome and Chronic Fatigue Syndrome.

Post-exertional malaise in Long COVID: subjective reporting versus objective assessment.

Long COVID-19: a Four-Year prospective cohort study of risk factors, recovery, and quality of life.

Autonomic Dysfunction in Patients with Acute Infection with Coxiella burnetii.

No reduced serum serotonin levels in patients with post-acute sequelae of COVID-19.

A comparison of genome-wide association analyses of persistent symptoms after Lyme disease, fibromyalgia, and myalgic encephalomyelitis - chronic fatigue syndrome.

Age-specific alterations of the gut mycobiome in patients with myalgic encephalomyelitis/chronic fatigue syndrome and identification of potential diagnostic biomarkers.

Long COVID in the population of COVID-19 hospitalized patients discharged from SUS' hospitals in Rio de Janeiro City, Brazil: a patient-engaged cohort survey study.

The Relationship Between Hemodynamic Responses During Head-Up Tilt Testing and Parameters of Infection in Post-COVID Syndrome, Chronic Fatigue Syndrome, and Late-Stage Lyme Disease.

Association between pre-existing chronic conditions and severity of first SARS-CoV-2 infection symptoms among adults living in Canada: a population-based survey analysis from January 2020 to August 2022.

In transfusion-dependent thalassemia, neuronal damage biomarkers are associated with affective and chronic fatigue symptoms.

Physical activity and sedentariness levels in patients with post-exertional malaise resulting from post-COVID-19 syndrome.

Health outcomes up to 3 years and post-exertional malaise in patients after hospitalization for COVID-19: a multicentre prospective cohort study (CO-FLOW).

Curated Collections

Neuroinflammation Evidence

Metabolism & Mitochondria

Biomarkers

PEM-Specific Research