What is Chronic Fatigue Syndrome?

Exhaustion, Pain, Flu-Like Symptoms

Woman collapsed on couch

Chronic fatigue syndrome (aka ME/CFS or SEID) is much more than just being tired a lot. People with ME/CFS are so run down that it interferes with their lives and can make it hard to function at all.

Some people with this disease say they have trouble staying on top of their responsibilities at home and on the job, while others are severely disabled and even bedridden.

Furthermore, they're not just dealing with extreme fatigue but with a wide range of other issues, including flu-like symptoms and chronic pain.

After decades of research, experts now believe that something called central sensitization is at least partially to blame for ME/CFS. "Central" refers to the central nervous system, which is made up of your brain and the nerves of the spinal cord. "Sensitization" means that it's become hyper-sensitive.

They also believe central sensitization is what makes ME/CFS so similar to fibromyalgia, which shares many of the same features.

The CDC says the first credible evidence of a biological basis for this condition came in 2006 when 20 researchers from different specialties each linked the illness with genes involved in the sympathetic nervous system and the HPA axis, which is your body's stress-response system. These genes control how your body responds to things like injuries, illness, and psychological stress.

Many researchers hypothesize that at least some cases are caused by an abnormal reaction to common infectious agents, including:

Studies haven't proved a consistent link to any one of these viruses, though.

Multiple studies suggest that the immune system may be chronically active in people with ME/CFS, which could at least partially explain the fatigue and lack of energy—basically, your body thinks it's fighting an infection, whether it is or not, and that takes a lot of energy.

Evidence for immune-system activation includes:

  • High levels of cells in the immune system called pro-inflammatory cytokines
  • Decreased function of natural killer (NK) cells, which help fight pathogens
  • Presence of autoantibodies (immune system cells that mistakenly attack healthy tissues)
  • Reduced response of T cells (a type of white blood cell) to specific viruses and/or bacteria

The research on this illness (under several different names) dates back to the 1700s. Through the centuries, it's been falsely attributed to various causes and is only now beginning to be better understood by medical science.

ME/CFS still goes by many names, including "chronic fatigue and immune dysfunction syndrome" (CFIDS), and "myalgic encephalomyelitis" (ME). Many patients and medical workers want to change the name, believing that the name "chronic fatigue syndrome" itself trivializes the condition and contributes to a continued misunderstanding of it.

Symptoms of Chronic Fatigue Syndrome

Each person with this illness has their own unique set of symptoms, and the intensity of symptoms varies from person to person. Fatigue, however, must be severe.

To meet that benchmark, your fatigue must meet the four following criteria:

  1. It's not relieved by sleep or rest
  2. It's not the result of strenuous physical labor
  3. It significantly lowers your ability to function normally in most situations
  4. It gets a lot worse after mental or physical exertion, or after you've been sick. This symptom is called post-exertional malaise, which is a steep increase in symptoms after exertion and an inability to repeat the activity the following day

Other common symptoms include:

  • Sudden and distinct onset, especially following a flu-like illness
  • Muscle and joint aches without swelling
  • Intense or changing patterns of headaches
  • Sore throat
  • Swollen lymph glands in the neck or armpits

Other symptoms can include:

  • Intolerance to alcohol
  • Irritable bowel syndrome (as an overlapping condition)
  • Dry eyes and mouth
  • Impaired circulation in the hands and feet
  • Visual disturbances
  • Painful menstrual periods

This might seem like a long list, but the full list of symptoms is actually much longer.

Getting a Diagnosis

ME/CFS is a diagnosis of exclusion, which means that other conditions with similar symptoms must be ruled out before your doctor can diagnose it.

So far, we don't have a blood test, scan, or anything else that's used as a diagnostic marker. The disease is therefore diagnosed based on symptoms and the lack of another explanation.

The diagnostic process for ME/CFS can be long and complicated.

Treatment Options

ME/CFS impacts more than a million people in the U.S. but we don't yet have any FDA-approved drugs for treating it. A host of medications are used off-label for it, though.

A typical treatment regimen can include prescription or over-the-counter medications to help with specific symptoms, supplements, complementary or alternative therapies, and emotional support. Some doctors prefer cognitive behavioral therapy and exercise of gradually increasing difficulty, but this approach is extremely controversial due to post-exertional malaise.

Some medical practitioners recommend dietary changes, yoga, and acupuncture.

Because ME/CFS can be an extremely stressful condition and can be made worse by stress, some people benefit from counseling, support groups, and ​stress-reduction techniques.

Most people with this disease need to experiment with multiple treatment options before they find a successful regimen.

A Word From Verywell

ME/CFS is a difficult condition to live with. However, in time, you can find treatments and learn coping strategies that help you live a full life.

And hope is on the horizon—we're getting closer to understanding what's going on in your body as well as how to better diagnose and treat it.


Lorusso L, et al. Autoimmunity Review. 2009 Feb;8(4):287-91. Immunological aspects of chronic fatigue syndrome.

Centers for Disease Control and Prevention. Press Briefing Transcripts: Chronic Fatigue Syndrome, April 2006.

University of Maryland Medical Center (UMMC). All rights reserved. "Chronic Fatigue Syndrome"