Chronic fatigue syndrome (CFS) 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 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 CFS. But because there is no definitive test for 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 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 CFS, the illness causes them to be confined to their home or bed for extended periods of time. 

Another defining characteristic of 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.

Chronic Fatigue Syndrome Symptoms

The main symptom of CFS is overwhelming exhaustion. The condition presents differently in different people, which is one of the reasons it is difficult to diagnose.

Most people diagnosed with CFS functioned at a high level prior to their illness. The development of severe fatigue is often abrupt and sometimes occurs after an infection or stressful event.

Additional symptoms are typically present in people with CFS and may also include some or all of the following:

  • Concentration or memory issues
  • Headaches, muscle aches, or joint pain
  • Sore throat
  • Tender lymph nodes
  • Difficulty sleeping
  • Lightheadedness when standing
  • Depression or anxiety

Chronic Fatigue Syndrome Symptoms in Children and Adolescents

Children generally exhibit symptoms of 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. Adolescents more often experience dizziness when standing and headaches and less often experience tender lymph nodes.

Causes of Chronic Fatigue Syndrome

A direct cause of CFS has not yet been discovered. Researchers are investigating several factors that may be linked to the development of CFS.

  • Infection: Many people describe an onset of 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 CFS has had one of these infections, and not everyone with an infection develops CFS.
  • Immune system differences: Researchers have identified differences in the amount and function of certain immune cells in people with CFS. They may play a role in the development of CFS by altering the way the immune system responds to infection.
  • Genetics: Relatives of people with CFS have a higher risk for developing CFS themselves. Some studies have identified genetic differences in people with CFS that may be linked to the condition.
  • Sleep loss: Limited studies have examined a possible connection between sleep deprivation and CFS. Some evidence suggests that people with 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 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 CFS, some people who develop long COVID also meet the criteria for a CFS diagnosis. In these cases, COVID-19 infection appears to be the trigger for the development of CFS. But scientists are conducting ongoing research to better understand the relationship between these two conditions. 

Risk Factors for Chronic Fatigue Syndrome

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

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

Chronic Fatigue Syndrome Diagnosis

As more research is conducted on CFS, the criteria for diagnosis continue to be updated. There are a few possible sets of criteria physicians may use to diagnose 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 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 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, including urine and blood tests. Physicians may also refer to specialists to ensure other diagnoses are ruled out.

Treatment for Chronic Fatigue Syndrome

A few different treatments are available to alleviate or manage symptoms. Unfortunately, there is no cure for 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 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 CFS may be prescribed medications to help with sleep, pain, depression, anxiety, and dizziness. 
  • Exercise: Exercise is an important part of managing 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): CBT aims to help people with CFS recognize and reframe fears about their condition and to learn practices that aid recovery. But the use of CBT as a treatment does not imply that CFS is psychological in origin. Recently, expert groups have questioned the strength of the evidence supporting the use of CBT to treat CFS though it remains a potential option for people with this condition. 

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

Talk to Your Doctor About Chronic Fatigue Syndrome

Anyone with concerns about persistent fatigue or 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.

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9 Sources

  1. Office on Women’s Health. (2021, February 22). Chronic fatigue syndrome., Retrieved February 7, 2023, from
  2. National Center for Emerging and Zoonotic Infectious Diseases, Division of High-Consequence Pathogens and Pathology. (2021, January 27). Myalgic encephalomyelitis/chronic fatigue syndrome. Centers for Disease Control and Prevention., Retrieved February 7, 2023, from
  3. 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
  4. Crawley E. (2018). Pediatric chronic fatigue syndrome: Current perspectives. Pediatric Health, Medicine and Therapeutics, 9, 27–33.
  5. 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.
  6. 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.
  7. 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).
  8. Gluckman, S. (2022, September). Chronic fatigue syndrome. Merck Manual Professional Version., Retrieved February 7, 2023, from
  9. Gluckman, S. J. (2021, June 24). Treatment of myalgic encephalomyelitis/chronic fatigue syndrome. In A. L. Komaroff (Ed.). UpToDate., Retrieved February 7, 2023, from

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