Key Takeaways
  • Chronic fatigue syndrome causes overwhelming fatigue that lasts longer than six months and is not resolved by sleeping.
  • Symptoms include severe exhaustion, sleep problems, cognitive impairments, and dizziness upon standing.
  • Treatments such as medication and sleep management strategies can lessen its impact on daily life.

Chronic fatigue syndrome, also called myalgic encephalomyelitis, is a potentially serious, debilitating, long-term illness marked by severe fatigue and other symptoms. It is normal to feel very tired after a sleepless night, a demanding week, or during periods of high stress. But a person with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) has fatigue that lasts at least six months that interferes with their ability to function and perform daily activities.

Researchers estimate that around 1 million people in the U.S. meet the criteria for ME/CFS. But because there is no definitive test for ME/CFS, most cases go undiagnosed. However, efforts are underway to better understand this condition, how to identify it, and potential treatment approaches. 

What Is Chronic Fatigue Syndrome?

People with ME/CFS experience persistent fatigue lasting longer than six months that does not get better with rest. The disorder can make it difficult to perform daily tasks, attend school, and maintain a job. For at least one-quarter of people with ME/CFS, the illness causes them to be confined to their home or bed for extended periods of time. 

Another defining characteristic of ME/CFS is that symptoms often get worse after engaging in physical or mental activity. The medical term for this experience is post-exertional malaise. People who experience post-exertional malaise may describe the new or worsening symptoms as a “crash,” which can last days or weeks.


The main symptom of ME/CFS is overwhelming exhaustion. The development of severe fatigue is often abrupt and sometimes occurs after an infection or stressful event. Most people functioned at a high level prior to their ME/CFS diagnosis. However, the condition presents differently in different people, which is one of the reasons it is difficult to diagnose.

Symptoms typically present in people with ME/CFS mayinclude some or all of the following:

  • Fatigue
  • Post-exertional malaise (PEM)
  • Unrefreshing sleep
  • Concentration or memory issues
  • Headaches or muscle pain
  • Sore throat
  • Tender lymph nodes
  • Lightheadedness when standing
  • Depression or anxiety

Chronic Fatigue Syndrome in Children

Children generally exhibit symptoms of ME/CFS that are similar to adults, but there are a few differences . Children younger than 12 years old are more likely to experience sore throat but less likely to report issues with sleep or mental function. Older children more often experience dizziness when standing and headaches and less often experience tender lymph nodes.


Although a direct cause has not yet been discovered, researchers are investigating several factors that may be linked to the development of ME/CFS.

  • Infection: Many people describe an onset of ME/CFS symptoms after a viral or bacterial infection, including a cold or flu, COVID-19, or mononucleosis caused by the Epstein Barr virus. However, not everyone with ME/CFS has had one of these infections, and not everyone with an infection develops ME/CFS.
  • Immune system differences: Researchers have identified differences in the amount and function of certain immune cells in people with ME/CFS. They may play a role in the development of ME/CFS by altering the way the immune system responds to infection.
  • Genetics: Relatives of people with ME/CFS have a higher risk for developing ME/CFS themselves. Some studies have identified genetic differences in people with ME/CFS that may be linked to the condition.
  • Sleep loss: Limited studies have examined a possible connection between sleep deprivation and ME/CFS. Some evidence suggests that people with ME/CFS sleep less and get less rapid eye movement (REM) sleep compared to people without the condition. However, more research is needed to determine whether sleep issues could contribute to the development of ME/CFS or not. 

Chronic Fatigue Syndrome and COVID-19

Chronic fatigue is one of the most common symptoms of “long COVID.” Long COVID is a condition that occurs when one or more COVID-19-related physical or mental symptoms persist for at least three months following infection. 

Because of the overlap in symptoms between long COVID and ME/CFS, some people who develop long COVID also meet the criteria for a ME/CFS diagnosis. In these cases, COVID-19 infection appears to be the trigger for the development of ME/CFS. But scientists are conducting ongoing research to better understand the relationship between these two conditions. 

Risk Factors

ME/CFS can occur in anyone, but the condition is more commonly found in women and people between the ages of 40 and 60. However, an estimated 90% of ME/CFS cases are undiagnosed , so some of these characteristics might better describe people who are more likely to receive a ME/CFS diagnosis than people who are most at risk. 

Barriers to receiving a diagnosis of ME/CFS include unequal access to health care services across different populations and insufficient education about ME/CFS among health professionals. 


There are a few possible sets of criteria physicians may use to diagnose ME/CFS. However, a commonly used guide from the Institute of Medicine requires a person to display the following three symptoms for at least six months to be diagnosed with ME/CSF:

  • Disruptive fatigue that does not resolve after resting
  • Worsened fatigue after performing usual activities
  • Unrefreshing sleep

Additionally, a person must have one of the following two symptoms:

  • Trouble with concentration or memory
  • Lightheadedness, dizziness, or fainting when standing upright

There is no ME/CFS test to verify whether or not a person has the condition. Instead, physicians collect information on a person’s symptoms and family history. They often conduct tests to rule out the possibility of other diseases, mood disorders, and sleep disorders. Physicians may also refer to specialists to ensure other diagnoses are ruled out.


A few different treatments are available to alleviate or manage symptoms. Unfortunately, there is no cure for ME/CFS at this time, but many people who engage in treatment do see improvements over time , especially when the disease is diagnosed and treated earlier. 

A health care provider will recommend a treatment plan that targets a person’s specific set of symptoms and other health conditions. It may include a combination of approaches. 

  • Sleep hygiene: Many people with ME/CFS struggle to sleep, so establishing healthy sleep habits is a common method for managing this condition. 
  • Medication: Depending on their symptoms, a person with ME/CFS may be prescribed medications to help with sleep, pain, depression, anxiety, and dizziness. 
  • Exercise: Exercise is an important part of managing ME/CFS. Approaches to exercise typically involve gradually and carefully increasing activity and exercise levels to avoid overexertion, either in a structured program or through close work with a doctor.
  • Cognitive behavioral therapy (CBT): Recently, expert groups have questioned the strength of the evidence supporting the use of CBT to treat ME/CFS. However, it remains a potential option for people with ME/CFS to learn practices that help aid in recovery and coping behaviors.  

Navigating a ME/CFS diagnosis and its symptoms can be challenging, discouraging, or isolating. If you are someone you love has been diagnosed with ME/CFS, you may find it helpful to connect with a support group locally or online. 

Talk to Your Doctor

Anyone with concerns about persistent fatigue or ME/CFS should consult a doctor. It might help to prepare for a medical appointment by keeping a health journal to track your activities and symptoms and note changes in your energy level. With the help of your doctor, you can discover or eliminate other possible causes of your fatigue. Then together you can develop a plan for treatment and symptom management.

Learn more about our Editorial Team

7 Sources

  1. Gluckman, S. J. (2022, May 9). Clinical features and diagnosis of myalgic encephalomyelitis/chronic fatigue syndrome. In A. L. Komaroff (Ed.). UpToDate., Retrieved February 7, 2023, from
  2. Crawley E. (2018). Pediatric chronic fatigue syndrome: Current perspectives. Pediatric Health, Medicine and Therapeutics, 9, 27–33.
  3. Nguyen, C. B., Alsøe, L., Lindvall, J. M., Sulheim, D., Fagermoen, E., Winger, A., Kaarbø, M., Nilsen, H., & Wyller, V. B. (2017). Whole blood gene expression in adolescent chronic fatigue syndrome: An exploratory cross-sectional study suggesting altered B cell differentiation and survival. Journal of Translational Medicine, 15(1), 102.
  4. Togo, F., Natelson, B. H., Cherniack, N. S., FitzGibbons, J., Garcon, C., & Rapoport, D. M. (2008). Sleep structure and sleepiness in chronic fatigue syndrome with or without coexisting fibromyalgia. Arthritis Research & Therapy, 10(3), R56.
  5. Committee on the Diagnostic Criteria for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome, Board on the Health of Select Populations, & Institute of Medicine. (2015). Beyond myalgic encephalomyelitis/chronic fatigue syndrome: Redefining an illness. National Academies Press (US).
  6. Gluckman, S. (2022, September). Chronic fatigue syndrome. Merck Manual Professional Version., Retrieved February 7, 2023, from
  7. Gluckman, S. J. (2021, June 24). Treatment of myalgic encephalomyelitis/chronic fatigue syndrome. In A. L. Komaroff (Ed.). UpToDate., Retrieved February 7, 2023, from

Learn How Chronic Fatigue Syndrome Affects Sleep

Chronic Fatigue Syndrome Treatments

By Jay Summer January 30, 2024

Chronic Fatigue Syndrome Symptoms

By Danielle Pacheco January 30, 2024
close quiz
We Are Here To Help You Sleep.
Tell us about your sleep by taking this brief quiz.

Based on your answers, we will calculate your free Sleep Foundation Score and create a personalized sleep profile that includes sleep-improving products and education curated just for you.

Saas Quiz Saas Quiz