Chronic Fatigue Syndrome

(CFS; Systemic Exertion Intolerance Disease; SEID; Myalgic Encephalomyelitis/Chronic Fatigue Syndrome; ME/CFS )


Chronic fatigue syndrome (CFS) is a condition that causes long-term, extreme tiredness. The tiredness is not relieved by bed rest. This can lead to problems doing daily activities.


The cause of CFS is not known. It may be linked to an infection or problems with the immune, endocrine, or nervous system.

Risk Factors

CFS is more common in women than men. It tends to be seen in adults ages 30 to 40 years old. However, CFS can happen at any age. Other things that raise the risk are:

  • Recent infection from a virus, fungus, or bacteria
  • Exposure to a toxin
  • Recent vaccination
  • Trauma—physical or emotional
  • Family history of CFS
  • An immune system problem
  • Long term stress
  • Allergies or sensitivities to foods, chemicals, odors, medicines, light, or noise


Symptoms vary from person to person. They may be:

  • New and lasting tiredness that:
    • Is not relieved with bed rest
    • Often gets worse with physical or mental activity
    • Cannot be explained by another health condition
  • Unexplained pain for more than 6 months, such as:
    • Muscle aches and headaches
    • Joint pain
    • Sore throat
    • Tender lymph nodes
  • Confusion, memory problems, and not being able to focus
  • Irritability, anxiety, panic attacks, mood swings, or depression
  • Problems sleeping
  • Vision problems
  • Lightheadedness, balance problems, or fainting
  • Chills and night sweats


The doctor will ask about your symptoms and health history. A physical exam may be done. There are no specific tests to diagnose CFS.

To diagnose CFS, the doctor must rule out other health conditions first. This may take a long time.


There is no cure for CFS. The goal is to manage symptoms and improve wellbeing. Treatment options are:


There are no current guidelines to prevent CFS.


Centers for Disease Control and Prevention
Solve ME/CFS Initiative


The College of Family Physicians of Canada


Bested A. Myalgic encephalomyelitis/chronic fatigue syndrome: insights & advances in care. Altern Ther Health Med. 2018;24(S1):32-33.
Chronic fatigue syndrome. Family Doctor—American Academy of Family Physicians website. Available at: Accessed February 26, 2021.
Myalgic encephalomyelitis/chronic fatigue syndrome. Centers for Disease Control and Prevention website. Available at: Accessed February 26, 2021.
Chronic fatigue syndrome. EBSCO DynaMed website. Available at: Accessed February 26, 2021.
Last reviewed January 2021 by EBSCO Medical Review Board Marcin Chwistek, MD
Last Updated: 2/26/2021

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