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Chronic fatigue syndrome/Systemic exertion intolerance disease

CFS; Fatigue - chronic; Immune dysfunction syndrome; Myalgic encephalomyelitis (ME); Myalgic encephalopathy chronic fatigue syndrome (ME-CFS); Systemic exertion intolerance disease (SEID)

Systemic exertion intolerance disease/chronic fatigue syndrome (SEID/CFS) is a long-term illness that affects many body systems. People with this illness are not able to do their usual activities. Sometimes, they may be confined to bed.

One common symptom is severe fatigue. It does not get better with rest and is not directly caused by other medical problems. Other symptoms can include problems with thinking and concentrating, pain, and dizziness.


The exact cause of SEID/CFS is unknown. It may have more than one cause. For example, two or more possible causes may work together to trigger the illness.

Researchers are looking into these possible causes:

  • Infection -- About 1 out of 10 people who develop certain infections, such as Epstein-Barr virus and Q fever, go on to develop SEID/CFS. Other infections have also been studied, but no one cause has been found.
  • Immune system changes -- SEID/CFS may be triggered by changes in the way a person's immune system responses to stress or illness.
  • Mental or physical stress -- Many people with SEID/CFS have been under serious mental or physical stress before becoming ill.
  • Energy production -- The way that cells within the body get energy is different in people with SEID/CFS than in people without the condition. It's unclear how this is linked to developing the illness.

Genetics or environmental factors may also play a role in the development of SEID/CFS:

  • Anyone can get SEID/CFS.
  • While most common in people between age 40 and 60 years old, the illness affects children, adolescents, and adults of all ages.
  • Among adults, women are affected more often than men.
  • Whites are diagnosed more than other races and ethnicities. But many people with SEID/CFS have not been diagnosed, particularly among minorities.


There are three main, or "core," symptoms in people with SEID/CFS:

  • Profound fatigue
  • Worsening symptoms after physical or mental activity
  • Sleep problems

People with SEID/CFS have persistent and profound fatigue and are unable to do activities they were able to do before the illness. This extreme fatigue is:

  • New
  • Lasts at least 6 months
  • Not due to unusual or intense activity
  • Not relieved by sleep or bed rest
  • Severe enough to keep you from participating in certain activities

SEID/CFS symptoms can become worse after physical or mental activity. This is called post-exertional malaise (PEM), also known as a crash, relapse, or collapse.

  • For example, you may experience a crash after shopping at the grocery store and need to take a nap before driving home. Or you may need someone to come pick you up.
  • There is no way to predict what will cause a crash or know how long it will take to recover. It can take days, weeks, or longer to recover.

Sleep issues may include problems falling or staying asleep. A full-night's rest does not relieve fatigue and other symptoms.

People with SEID/CFS also often experience at least one of the two following symptoms:

  • Forgetfulness, concentration problems, problems following details (also called "brain fog")
  • Worsening symptoms when standing or sitting upright. This is called orthostatic intolerance. You may feel dizzy, lightheaded, or faint when standing or sitting up. You also may have vision changes or see spots.

Other common symptoms include:

  • Joint pain without swelling or redness, muscle aches, muscle weakness all over, or headaches that differ from those you have had in the past
  • Sore throat, sore lymph nodes in the neck or under the arms, chills and night sweats
  • Digestive problems, such as irritable bowel syndrome
  • Allergies
  • Sensitivity to noise, food, odors, or chemicals

Exams and Tests

The Centers for Disease Control (CDC) describes SEID/CFS as a distinct disorder with specific symptoms and physical signs. Diagnosis is based on ruling out other possible causes.

Your health care provider will try to rule out other possible causes of fatigue, including:

  • Drug dependence
  • Immune or autoimmune disorders
  • Infections
  • Muscle or nerve diseases (such as multiple sclerosis)
  • Endocrine diseases (such as hypothyroidism)
  • Other illnesses (such as heart, kidney, or liver diseases)
  • Psychiatric or psychological illnesses, particularly depression
  • Tumors

A diagnosis of SEID/CFS must include:

  • Absence of other causes of long-term (chronic) fatigue
  • At least four SEID/CFS-specific symptoms
  • Extreme, long-term fatigue

There are no specific tests to confirm the diagnosis of SEID/CFS. However, there have been reports of people with SEID/CFS having abnormal results on the following tests:

  • Brain MRI
  • White blood cell count


There is currently no cure for SEID/CFS. The goal of treatment is to relieve symptoms.

Treatment includes a combination of the following:

  • Sleep management techniques
  • Medicines to reduce pain, discomfort, and fever
  • Medicines to treat anxiety (anti-anxiety drugs)
  • Medicines to treat depression (antidepressant drugs)
  • Healthy diet

Some drugs can cause reactions or side effects that are worse than the original symptoms of the disease.

People with SEID/CFS are encouraged to maintain an active social life. Mild physical exercise may also be helpful. Your health care team will help you figure out how much activity you can do, and how to slowly increase your activity. Tips include:

  • Avoid doing too much on days when you feel tired
  • Balance your time between activity, rest, and sleep
  • Break big tasks into smaller, more manageable ones
  • Spread out your more challenging tasks through the week

Relaxation and stress-reduction techniques can help manage chronic (long-term) pain and fatigue. They are not used as the primary treatment for SEID/CFS. Relaxation techniques include:

  • Biofeedback
  • Deep breathing exercises
  • Hypnosis
  • Massage therapy
  • Meditation
  • Muscle relaxation techniques
  • Yoga

It also may be helpful to work with a therapist to help you deal with your feelings and the impact of the illness on your life.

Newer medicine approaches are being researched.

Support Groups

Some people may benefit from taking part in an SEID/CFS support group.

Outlook (Prognosis)

The long-term outlook for people with SEID/CFS varies. It is hard to predict when symptoms first start. Some people completely recover after 6 months to a year.

About 1 in 4 people with SEID/CFS are so severely disabled that they can't get out of bed or leave their home. Symptoms can come and go in cycles, and even when people feel better, they may experience a relapse triggered by exertion or an unknown cause.

Some people never feel like they did before they developed SEID/CFS. Studies suggest that you are more likely to get better if you receive extensive rehabilitation.

Possible Complications

Complications may include:

  • Depression
  • Inability to take part in work and social activities, which can lead to isolation
  • Side effects from medicines or treatments

When to Contact a Medical Professional

Call your provider if you have severe fatigue, with or without other symptoms of this disorder. Other more serious disorders can cause similar symptoms and should be ruled out.


Bennett RM. Fibromyalgia, chronic fatigue syndrome, and myofascial pain. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 274.

Centers for Disease Control and Prevention website. Myalgic encephalomyelitis/chronic fatigue syndrome: treatment. Updated May 18, 2018. Accessed July 10, 2018.

Committee on the Diagnostic Criteria for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome; Board on the Health of Select Populations; Institute of Medicine. Beyond myalgic encephalomyelitis/chronic fatigue syndrome: redefining an illness. Washington (DC): National Academies Press (US); 2015. PMID: 25695122

Engleberg NC. Chronic fatigue syndrome. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, Updated Edition. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 133.

Nijs J, Roussel N, Van Oosterwijck J, et al. Fear of movement and avoidance behaviour toward physical activity in chronic-fatigue syndrome and fibromyalgia: state of the art and implications for clinical practice. Clin Rheumatol. 2013;32(8):1121-1129. PMID: 23639990

Smith ME, Haney E, McDonagh M, et al. Treatment of myalgic encephalomyelitis/chronic fatigue syndrome: a systematic review for a National Institutes of Health Pathways to Prevention Workshop. Ann Intern Med. 2015;162(12):841-850. PMID: 26075755

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Review Date: 4/12/2018

Reviewed By: Gordon A. Starkebaum, MD, ABIM Board Certified in Rheumatology, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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