What Is Chronic Fatigue Syndrome?

CFS is a complex condition with unclear causes, but there are ways to help reduce fatigue and manage the condition.

Fatigued woman sitting on her couch, eyes closed with head in hand

Updated on February 1, 2024.

Everyone gets tired, whether it’s from a tough workout or just doing errands. But if even a little exercise drains your energy completely every time or you can’t mildly exert yourself for just a few minutes, you may have a debilitating condition called chronic fatigue syndrome. It causes severe fatigue that, by definition, lasts for more than six months. Other symptoms may include pain, headaches, brain fog, and sleep problems. 

While chronic fatigue syndrome (CFS) is the most commonly used term for the condition, healthcare providers (HCPs) may also refer to it as myalgic encephalomyelitis (ME), myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), or systemic exertion intolerance disease (SEID).

SEID is a name that the Institute of Medicine (now called the National Academy of Medicine) recommended be used to name the condition in an attempt to more accurately capture the symptoms of the disease, explains Lela Mansoori, MD, an endocrinologist and internist in Denver, Colorado. “It’s not just fatigue, it’s the inability for people to exert themselves.” 

The condition may affect as many as 2.5 million people in the United States, although it’s estimated that up to 90 percent of cases are undiagnosed. Finding relief for CFS starts with a diagnosis, but given the complexity of the condition, that is no easy task. 

What is chronic fatigue syndrome? 

“The symptom of fatigue is present in many illnesses,” says Dr. Mansoori. “Diagnosing the condition is basically a diagnosis of exclusion.” HCPs have to rule out a number of conditions before settling on a diagnosis of CFS. Mansoori says she first checks for neurologic conditions like multiple sclerosis or a malignancy, other types of cancers, autoimmune diseases like arthritis or lupus, infectious diseases such as hepatitis or HIV, thyroid disorders and adrenal disorders. 

While the actual cause remains a medical mystery, there are several hypotheses, says Mansoori. Depression is often blamed for chronic fatigue syndrome, but depression is most likely associated with the condition rather than causing it. There’s evidence that childhood trauma increases the risk of developing chronic fatigue syndrome by up to six times, according to Mansoori, but the true cause remains unknown. 

Is there a link between chronic fatigue syndrome and inflammation? 

A July 2017 study published in Proceedings of the National Academy of Sciences suggested that chronic fatigue syndrome might be caused in part by inflammation. Researchers found higher levels of 17 immune system chemicals called cytokines—13 of which are associated with inflammation—in the bloodstreams of people with chronic fatigue. 

The more of these chemicals that were in the blood, the worse chronic fatigue symptoms were. Researchers think this may help pave the way for blood tests to help diagnose cases of suspected chronic fatigue syndrome.  

There are many similarities between chronic fatigue syndrome and fibromyalgia, another condition with no known causes. Some researchers believe they are the same disease, just different expressions of the symptoms. 

What does chronic fatigue syndrome feel like? 

Symptoms of chronic fatigue syndrome are often both physical and mental. “People may feel like they have to nap several times a day and they have problems staying asleep or waking up too early,” says Mansoori. “They may feel drained after just mild activity like sweeping the floor or going for a walk. Their thought processes feel slow and an overwhelming number have problems with memory.” She says that patients may also report flu-like symptoms, along with heaviness in the arms and legs. 

“Also, because of these symptoms, patients feel that their social interactions decrease, which leads to increased isolation,” says Mansoori. She says a patient may feel depressed not from the condition but because of the many limitations on regular activities. 

The National Academy of Medicine’s expert panel released a report in February 2015 with new diagnostic criteria. To receive a diagnosis of CFS, a patient must have these symptoms: 

  • Being fatigued and unable to function for at least six months 
  • Exhaustion after exerting oneself 
  • Unrefreshing sleep 

And at least one of the following: 

  • Cognitive impairment, like trouble remembering or expressing thoughts 
  • Dizziness when sitting up or standing up quickly 

Treatment options 

There is no cure for chronic fatigue syndrome and treatment options are few, says Mansoori. Graded Exercise Therapy (GET) is often used to treat it. “GET involves a physical activity schedule that increases the patient’s activity level over time,” she says. The aim is to slowly reintroduce exercise and exertion into the patient’s life without overwhelming them. 

Chronic fatigue syndrome has a strong mental health component as well. For that reason, cognitive behavioral therapy (CBT) is sometimes recommended. Research suggests that cognitive behavioral therapy can help with the symptom of post-exertional exhaustion as effectively as exercise can. “Most patients rated themselves as feeling much better,” says Mansoori. It’s important to see a CBT therapist that specializes in chronic fatigue syndrome, Mansoori notes. 

“There are also some pharmacologic therapies, but compared to GET and cognitive behavioral therapy, medication has the most disappointing results,” says Mansoori. “There’s really no good evidence to support steroids or antiviral medication to treat the condition.” 

What you can do 

Still, there are things you can do to help yourself feel better if you experience chronic fatigue syndrome. The first is to talk to your HCP about GET, therapy, and any other recommendations. You can also: 

  • Keep a diary to help spot what triggers your fatigue. It can help you identify what might be worsening it, along with times during the day when your energy is usually highest and lowest. Use that information to plan your activities. 
  • Ensure that you understand any tasks you must do and keep distractions to a minimum to try to ease brain fog. 
  • Be positive. Don’t use negative self-talk, enforcing the idea that you can’t cope with your condition. Instead, be proactive and learn what works for you to manage low energy and other symptoms. 
  • Maintain a regular bedtime routine and consistent wakeup and sleep times as another strategy for reducing daytime fatigue.
Article sources open article sources

Adamson J, Ali S, Santhouse A, Wessely S, Chalder T. Cognitive behavioural therapy for chronic fatigue and chronic fatigue syndrome: Outcomes from a specialist clinic in the UK. J R Soc Med. 2020;113(10):394-402.    
Centers for Disease Control and Prevention. Diagnosis of ME/CFS. Last reviewed January 27, 2021.   
Centers for Disease Control and Prevention. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome – Information for Healthcare Providers. Additional Strategies for Living with ME/CFS. Last reviewed April 30, 2021.  
Centers for Disease Control and Prevention. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. IOM 2015 Diagnostic Criteria. Page last reviewed: April 27, 2021. 
Centers for Disease Control and Prevention. Treatment of ME/CFS. Last reviewed January 28, 2021.  
Centers for Disease Control and Prevention. What is ME/CFS? Last reviewed March 21, 2023.
MedlinePlus. Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Review Date April 30, 2023. 
Mount Sinai. Chronic fatigue syndrome. Accessed February 1, 2024.

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