Search and filter 6,209 studies by evidence level, diagnostic criteria, PEM status, and research domain. Each entry links to the original source.
Studies sorted by evidence level, then year. Browse by topic instead →
Evidence level (E0–E3) reflects study type and replication, not methodological quality. A weak systematic review still sits at E0. How evidence levels work →
3701–3720 of 6,209 studies
Jacobson, W, Saich, T, Borysiewicz, L K et al.·Neurology·1993
Researchers measured folic acid levels in the blood of 60 ME/CFS patients and found that about half had lower-than-normal amounts. This suggests that some people with ME/CFS may not have enough folic acid in their body, which is a B vitamin important for many body functions.
McDonald, E, David, A S, Pelosi, A J et al.·Psychological medicine·1993
Researchers studied 77 primary care patients with chronic fatigue and found that 26% met criteria for chronic fatigue syndrome (CFS). Most patients received other diagnoses, including depression and a condition called neurasthenia. Interestingly, patients seen in general practice were more likely to recognize that stress and emotional factors played a role in their fatigue, unlike hospital patients who often blamed purely physical causes like viruses.
Honda, M, Kitamura, K, Nakasone, T et al.·Microbiology and immunology·1993
This study tested 30 Japanese patients with ME/CFS to see if they had been infected with certain viruses called retroviruses, which some researchers thought might cause the illness. Using multiple testing methods, the researchers found that none of the patients had these viral infections. This suggests that these particular known viruses are not responsible for causing ME/CFS in this Japanese patient population.
Ray, C, Phillips, L, Weir, W R·The British journal of clinical psychology·1993
Many people with ME/CFS report problems with attention and concentration in daily life. This study compared ME/CFS patients with healthy people using questionnaires about attention problems and computer-based attention tests. Patients reported significantly more attention difficulties than controls, though standard attention tests didn't show clear differences. Interestingly, patients were slower at processing tasks like reading words and naming colors, suggesting their thinking speed may be affected rather than their ability to focus.
Langsjoen, P H, Langsjoen, P H, Folkers, K·The Clinical investigator·1993
This study looked at heart function in patients with chronic fatigue syndrome (ME/CFS) and compared them to patients with other heart conditions. Researchers found that many of these patients had a specific type of heart problem called diastolic dysfunction—where the heart doesn't relax properly between beats. When patients were given a supplement called CoQ10, their heart function improved and their symptoms got better.
Centers for Disease Control and Prevention (CDC)·MMWR. Morbidity and mortality weekly report·1993
In the early 1990s, some laboratories were offering blood tests to check if people with ME/CFS had been infected with certain viruses called retroviruses. This CDC study tested whether three of these commercial tests could actually tell the difference between people with ME/CFS and healthy people. The researchers found that these tests could not reliably distinguish between the two groups, meaning the tests were not accurate for identifying ME/CFS.
Eymard, D, Lebel, F, Miller, M et al.·The Canadian journal of infectious diseases = Journal canadien des maladies infectieuses·1993
This study compared antibody levels against human herpesvirus 6 (HHV-6) in two groups: people with ME/CFS and people with chronic fatigue who didn't meet the official ME/CFS diagnosis. Researchers found that people with ME/CFS had significantly higher antibody levels against HHV-6, suggesting the virus might play a role in the condition. The study also found that sore throat, headache, and recurrent fatigue were more common in the ME/CFS group.
Bates, D W, Schmitt, W, Buchwald, D et al.·Archives of internal medicine·1993
This study looked at how common severe, long-lasting fatigue is in a primary care doctor's office and how often it is ME/CFS. Researchers found that while about 27% of patients had long-term fatigue affecting their daily life, most could be explained by other medical or mental health conditions. Only about 0.3% to 1% of patients actually had ME/CFS, depending on which diagnostic criteria were used.
DeLuca, J, Johnson, S K, Natelson, B H·Archives of neurology·1993
This study compared thinking and concentration abilities in people with ME/CFS, people with multiple sclerosis (MS), and healthy volunteers. All participants were matched by age and education level. People with ME/CFS and MS both showed difficulty with tasks requiring fast, complex thinking compared to healthy controls, suggesting that ME/CFS may affect how the brain processes information.
Lerner, A M, Lawrie, C, Dworkin, H S·Chest·1993
This study looked at heart activity recorded over 24 hours in ME/CFS patients compared to others. All 24 ME/CFS patients showed unusual patterns on their heart monitors (abnormal T waves), compared to only 22% of people without ME/CFS. Further testing found that 8 out of 60 ME/CFS patients had mild heart pumping problems that only showed up during exercise, even though their resting heart function appeared normal. The researchers suggest ME/CFS fatigue might be related to the heart not working well during normal daily activities.
Bowles, N E, Bayston, T A, Zhang, H Y et al.·Journal of medicine·1993
Researchers tested muscle samples from people with post-viral fatigue syndrome (a condition similar to ME/CFS that develops after a viral infection) and found evidence of enterovirus RNA in about 26% of samples. This was much higher than in healthy control samples. The study suggests that some cases of ME/CFS may develop after a viral infection causes inflammation in the muscles, similar to how viral heart infections can lead to long-term heart problems.
Nørregaard, J, Bülow, P M, Prescott, E et al.·Scandinavian journal of rheumatology·1993
This study followed 91 fibromyalgia patients for about 4 years to see if their muscle pain was caused by other medical conditions and how their symptoms changed over time. Most patients reported their pain got worse, and while many experienced severe fatigue, very few actually met the diagnostic criteria for chronic fatigue syndrome. The good news was that muscle strength remained stable and most cases of fibromyalgia were not caused by an underlying disease.
CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne·1992
This 1992 study examined whether the hepatitis B vaccine might be linked to ME/CFS. Researchers looked at cases where people reported developing chronic fatigue symptoms after receiving the vaccine. This early observation-based study raised questions about a possible connection that researchers wanted to investigate further.
Lloyd, A, Hickie, I, Hickie, C et al.·Clinical and experimental immunology·1992
This study compared immune system function in patients with ME/CFS, people with depression, and healthy individuals. Researchers found that ME/CFS patients had weaker immune responses than both groups, suggesting their immune problems are distinct from depression-related immune changes. This indicates that ME/CFS involves direct immune system dysfunction rather than these problems simply being caused by depression.
Matsuda, J, Gohchi, K·Nihon rinsho. Japanese journal of clinical medicine·1992
Researchers studied 285 people who reported severe fatigue, and confirmed that 55 of them actually had chronic fatigue syndrome (CFS) using official diagnostic criteria. They tested patients' blood for signs of viral infections and measured certain immune cell markers to understand what might be causing CFS. This study looked at various biological factors that could explain why people develop this condition.
Levine, P H, Peterson, D, McNamee, F L et al.·Cancer research·1992
Some people with ME/CFS have reported concerns about developing lymphoma (a type of blood cancer). This study looked at cancer rates in Nevada before and after documented ME/CFS outbreaks in the mid-1980s to see if there was an increase in non-Hodgkin's lymphoma cases. The researchers found that cancer rates followed the same patterns as the rest of the country, with no unusual spike linked to ME/CFS.
Kawai, K, Kawai, A·Internal medicine (Tokyo, Japan)·1992
This study examined whether Epstein-Barr virus (EBV), a common virus that causes infectious mononucleosis, might be connected to chronic fatigue syndrome (CFS). Researchers tested 22 patients with long-lasting fatigue and found that those with definite CFS had higher levels of certain EBV antibodies compared to patients with milder symptoms and healthy controls. The study suggests a possible link between EBV activation and the severity of fatigue experienced.
Price, R K, North, C S, Wessely, S et al.·Public health reports (Washington, D.C. : 1974)·1992
This study looked at how common chronic fatigue syndrome (CFS) is in the general population by surveying over 13,500 people between 1981 and 1984. Researchers found that while about 23% of people reported experiencing persistent fatigue at some point in their lives, actual CFS meeting strict diagnostic criteria was extremely rare—only 1 person in the entire study group had the condition. When researchers excluded people with other medical or psychiatric illnesses, CFS became even rarer.
Lloyd, A R, Pender, H·The Medical journal of Australia·1992
This study looked at how much money ME/CFS costs—not just for patients themselves, but for the healthcare system and society overall. Researchers surveyed 42 patients in one Australian region about their medical expenses and lost income, then used those numbers to estimate what ME/CFS might cost across all of Australia. They found the disease creates a huge financial burden that had been largely overlooked by policymakers.
Nishikai, M·Nihon rinsho. Japanese journal of clinical medicine·1992
This study examined 51 patients with ME/CFS to look for physical and immune system clues about the illness. Researchers found that most patients had tender points similar to those seen in fibromyalgia, elevated antibodies to Epstein-Barr virus (a common virus), and lower numbers of certain immune cells called NK cells. These findings suggest that viral infections and immune system problems may play a role in ME/CFS.
Or browse by topic
Thematic groupings by clinical question or research area.
PET imaging and other studies providing evidence for brain inflammation in ME/CFS.
NeurologyMetabolomics and mitochondrial function studies revealing energy metabolism disruption.
MetabolismStudies identifying potential biological markers for ME/CFS diagnosis and stratification.
Biomarker