Understanding Chronic Fatigue Syndrome

Symptoms of this condition, also known as myalgic encephalomyelitis, often overlap with long COVID, fibromyalgia and others.

Updated by Linda Rath | June 30, 2023

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex illness marked by profound exhaustion that lasts at least six months. Symptoms get worse with normal mental or physical activity and are not relieved by rest. It’s different from the deep tiredness you may feel from a demanding job, too many late nights, stress or depression. Exhaustion in CFS is long-lasting and may not have a clear cause. Severity varies from one person to another, but about a quarter of people with the disorder may be bedridden or homebound at least some of the time. Only a small proportion ever fully recover.
Not the Flu
It’s sometimes said that ME/CFS symptoms resemble the flu, but that’s not quite right. It can develop after an infection like the flu, Lyme disease, Epstein-Barr, mononucleosis or COVID-19. And while some symptoms are flu-like, especially chronic muscle and joint pain, they aren’t defining features of the disease. The most important symptoms are unique to ME/CFS and similar conditions. They include:  

  • Exhaustion lasting longer than six months that interferes with the ability to work, go to school, socialize or perform daily chores. 
  • Post-exertional malaise (PEM), worsening symptoms after physical or mental activities that didn’t previously cause problems. Recovery from PEM can take days or weeks. According to the National Institutes of Health, PEM is also the predominant symptom of long COVID.
  • Poor sleep that doesn’t relieve symptoms and may make them worse.
  • Problems with thinking and memory, sometimes called brain fog
  • Orthostatic intolerance, meaning symptoms get worse when going from sitting to standing. Postural orthostatic tachycardia syndrome (POTS), which causes a racing heart and dizziness on standing, is common in both ME/CFS and long COVID.

ME/CFS is diagnosed when someone has four of the five main symptoms listed above. Symptoms must be moderate or severe at least half the time.

Dubious History 

ME/CFS, once called neurasthenia, has an unfortunate but familiar history. Beginning in the mid-1800s, severe exhaustion was believed to result from a society that had become too fast-paced for the human body’s own good. Although men could develop neurasthenia, it was diagnosed far more often in women, especially those who “thought too much” or worked outside the home. It was either ignored and ridiculed by the medical establishment or, more often, treated with lengthy rest cures and dubious tonics. Chronic fatigue still isn’t included in most medical school curricula, and some doctors continue to dismiss it as a psychosomatic illness. Yet ME/CFS is a real physical disorder with potentially life-altering symptoms. 


It’s not clear why some people develop ME/CFS. It’s a complicated disease that likely has many causes. Sometimes it follows an infection or severe emotional stress. It can also result from:

  • Abnormal changes in the autonomic nervous system, which regulates vital functions like heart rate, digestion and body temperature. POTS, an autonomic disorder, affects about 1% of the population and is especially common in people with ME/CFS or long COVID.
  • Immune system problems, like autoimmune forms of arthritis, where the body attacks its own tissues. Many people with ME/CFS also have fibromyalgia or an autoimmune disease.
  • Defects in the body’s energy chemistry.
  • Dysbiosis – an unhealthy imbalance in the microbial ecosystem in the gut. 
  • Inability to get enough oxygen and blood to muscle tissue. 

Who Gets It

About one in eight people is believed to have ME/CFS, although as many as 90% of cases may be undiagnosed. It can affect anyone but is most common in younger adults and those assigned female at birth.  It’s also more common in people of color than in whites. 


There is no cure or specific treatment for ME/CFS. Doctors are likely to recommend certain lifestyle changes to reduce symptoms and help maintain and build strength.

  • Physical pacing. This is one of the most important but also most challenging aspects of treating ME/CFS. Patients first must figure out what level of activity triggers post-exertional symptoms. Then, working with a physical therapist or personal trainer experienced in ME/CFS, they can begin a gentle exercise program that aims to increase in intensity while preventing PEM. Research shows that ME/CFS patients feel and sleep better and have more energy with exercise. 
  • Mental pacing. As with physical pacing, it’s important to avoid intense mental work that might trigger a reaction. Many people need to scale back what they once did on the job or in school.
  • Manage orthostatic symptoms. Adding more salt to the diet, drinking plenty of water and wearing compression hose can help stabilize blood pressure.
  • Improve sleep. Do you toss and turn even when you follow all the rules of sleep hygiene – cool, dark bedroom, no large meals, alcohol or screens before bed? Then consider meditation, free sleep apps like Calm, or cognitive behavioral therapy for insomnia (CBT-i), which is also available on various evidence-based apps.
  • Avoid trigger foods. Stay away from foods that aggravate symptoms, especially sugar, alcohol and caffeine. People with ME/CFS often have food sensitivities; a food diary can help you track the most troublesome. 
  • Try unsaturated fatty acids. Evidence suggests that fish oil supplements or foods rich in unsaturated fatty acids such as wild salmon, olive oil and nuts may reduce inflammation in ME/CFS. 
  • Consider traditional Chinese medicine. Herbs, acupuncture and other traditional Chinese therapies have been shown in randomized controlled trials to achieve excellent results for ME/CFS, often outperforming conventional approaches. Many private insurers cover acupuncture for various indications. Medicare covers it for back pain only and limits the number of treatments.

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