Chronic Fatigue Syndrome

Also known as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) or systemic exertion intolerance disease (SEID)

Medically reviewed by Scott Zashin, MD
Updated on June 23, 2023

Chronic fatigue syndrome is a condition that generally involves deep fatigue, unrefreshing sleep, exercise intolerance, and neurological issues referred to as “brain fog.” The exact cause of chronic fatigue syndrome is unknown but is believed to be a combination of genetic predisposition and environmental factors. With no simple test to identify it currently available, diagnosis is based on symptoms and the exclusion of other causes. Treatment is aimed at making lifestyle changes that help alleviate the condition and relieve symptoms with medications and therapies.

Understanding CFS

A woman feeling fatigue and exhaustion
Chronic Fatigue Syndrome: Symptoms, Treatment, Tests
An exhausted young woman lies in bed.
Fibromyalgia vs Chronic Fatigue Syndrome: What's the Difference?
Nurse draws blood
Why Is Chronic Fatigue Syndrome So Difficult to Diagnose?
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The Root of Chronic Fatigue Syndrome

Frequently Asked Questions

  • What are the symptoms of chronic fatigue syndrome?

    Symptoms of chronic fatigue syndrome often vary. According to the National Academy of Medicine, fatigue, post-exertional malaise, and sleep problems must all be present in order to diagnose the condition. In addition, a patient must be experiencing either cognitive impairment (brain fog) or a worsening of symptoms while upright (orthostatic intolerance).

    Learn More: Symptoms of Chronic Fatigue Syndrome
  • What kind of doctor diagnoses chronic fatigue syndrome?

    Many primary care doctors will be able to diagnose chronic fatigue syndrome. They may also refer you to a doctor who is knowledgeable about or specializes in fatigue disorders, or you may choose to seek out such a practitioner yourself. Physicians who specialize in treating Lyme disease and other autoimmune disorders may also have experience treating patients with chronic fatigue syndrome.

    Learn More: How Chronic Fatigue Syndrome Is Diagnosed
  • What causes chronic fatigue syndrome?

    While the causes of chronic fatigue syndrome are still unclear, the condition has been linked to a number of factors, including genetics; viral or other infections; hormone, immune, or central nervous system dysregulation; stress; and exposure to toxins. Some researchers believe the condition may result from several of these factors coming together under the right conditions.

    Learn More: Causes and Risk Factors of Chronic Fatigue Syndrome
  • How long does chronic fatigue syndrome last?

    By definition, chronic fatigue syndrome persists for months or years. Recovering from it often hinges on eliminating possible causes, as well as discovering a treatment protocol tailored to your individual body, symptoms, and triggers.

    Learn More: Track Your Symptoms of Fibromyalgia and ME/CFS

Symptoms

fatigue, chronic fatigue syndrome, fibromyalgia, hashimoto's
The Many Faces of Chronic Fatigue Syndrome
Young woman lying on bed with hands clasped on forehead, looking up in thought
Unrefreshing Sleep May Be the Reason Why You Are Exhausted After Rest
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How to Tell If You Have Chronic Fatigue Syndrome
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Heavy Sweating in Fibromyalgia and Chronic Fatigue Syndrome
Dizzy man in bed.
How to Treat Dizziness and Fatigue in ME/CFS

Key Terms

  • Brain Fog

    Brain fog is characterized by mental confusion and fatigue. It may feel as if your brain is working more slowly than usual, and you may have slowed reaction times. You may also experience problems with short-term memory, visual perception, or tuning out distractions. Also known as “fibro fog,” these neurological symptoms are common in fibromyalgia and chronic fatigue syndrome.

    Fibro Fog and ME/CFS Brain Fog
  • Fibromyalgia Syndrome

    Many people with chronic fatigue syndrome (CFS) fit the criteria for fibromyalgia syndrome, and vice versa. There is ongoing confusion as to whether these are different conditions or variations of the same disorder. The difference is that CFS has a primary symptom of fatigue, while fibromyalgia has a primary symptom of pain.

    Fibromyalgia
  • Hypothalamic-Pituitary-Adrenal Axis:

    The hypothalamic-pituitary-adrenal axis controls your response to stress, regulates sleep, and is involved in mood disorders such as depression. Some research suggests that disruption or dysregulation of the sympathetic nervous system and the hormones involved in the HPA axis may be involved in chronic fatigue syndrome.

    Causes and Risk Factors of Chronic Fatigue Syndrome
  • Post-Exertional Malaise

    Post-exertional malaise causes a spike in symptoms of chronic fatigue syndrome and an energy crash after what, to others, may seem like minor exertion.  Many people report that pacing activity according to energy level—perhaps alternating activity with naps or other types of rest—is helpful for managing this common symptom of chronic fatigue syndrome and fibromyalgia.

    Post-Exertional Malaise and Its Symptoms and Triggers

Treatment

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Feeling Better When You Have Chronic Fatigue Syndrome
Tired woman sitting on the edge of bed
What Is Post-Exertional Malaise? Learn About a Key ME/CFS Symptom
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How ADHD Drugs Can Help ME/CFS Symptoms

Explore Chronic Fatigue Syndrome

Page Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

  1. Centers for Disease Control and Prevention. Myalgic encephalomyelitis/chronic fatigue syndrome basics.

  2. Centers for Disease Control and Prevention. Myalgic encephalomyelitis/chronic fatigue syndrome: IOM 2015 diagnostic criteria.

  3. Natelson BH. Myalgic encephalomyelitis/chronic fatigue syndrome and fibromyalgia: definitions, similarities, and differences. Clin Ther. 2019;41(4):612-618. doi:10.1016/j.clinthera.2018.12.016

  4.  Tomas C, Newton J, Watson S. A review of hypothalamic-pituitary-adrenal axis function in chronic fatigue syndrome. ISRN Neurosci. 2013;2013:784520. doi:10.1155/2013/784520

  5. McGregor NR, Armstrong CW, Lewis DP, Gooley PR. Post-exertional malaise is associated with hypermetabolism, hypoacetylation and purine metabolism deregulation in ME/CFS cases. Diagnostics (Basel). 2019;9(3):70. Published 2019 Jul 4. doi:10.3390/diagnostics9030070

  6. Goudsmit EM, Nijs J, Jason LA, Wallman KE. Pacing as a strategy to improve energy management in myalgic encephalomyelitis/chronic fatigue syndrome: A consensus document. Disabil Rehabil. 2012;34(13):1140-7. doi:10.3109/09638288.2011.635746