Introduction 

Chronic fatigue syndrome (CFS) causes persistent fatigue (exhaustion) that affects everyday life and doesn't go away with sleep or rest. 

CFS is also known as ME, which stands for myalgic encephalomyelitis. Myalgia means muscle pain and encephalomyelitis means inflammation of the brain and spinal cord. Both CFS and ME are commonly used terms (see box on this page).

Sometimes the term 'myalgic encephalopathy' is used. Encephalopathy means a condition that affects brain function.

CFS is a serious condition that can cause long-term illness and disability, but many people – particularly children and young people – improve over time.

Who is affected

It is estimated that around 250,000 people in the UK have CFS.

Anyone can get CFS, although it is more common in women than in men. It usually develops in the early 20s to mid-40s. Children can also be affected, usually between the ages of 13 and 15. 

How it affects quality of life

Most cases of CFS are mild or moderate, but up to one in four people with CFS have severe symptoms. These are defined as follows: 

  • Mild: you are able to care for yourself, but may need days off work to rest. 
  • Moderate: you may have reduced mobility, and your symptoms can vary. You may also have disturbed sleep patterns, and need to sleep in the afternoon.
  • Severe: you are able to carry out minimal daily tasks, such as brushing your teeth, but you have significantly reduced mobility. You may also have difficulty concentrating.

Read more about the symptoms of CFS.

Why it happens

It is not known exactly what causes CFS.

Various theories have been suggested, including:

  • a viral infection
  • problems with the immune system
  • an imbalance of hormones
  • psychiatric problems, such as stress and emotional trauma

Some people are thought to be more susceptible to the condition due to their genes, as the condition is more common in some families.

More research is needed to confirm exactly what causes the condition.

Read more about the causes of CFS.

How it is diagnosed

There are specific guidelines issued by the National Institute for Health and Care Excellence (NICE) about the diagnosis and management of CFS.

NICE says that a diagnosis of CFS should be considered if you meet specific criteria regarding your fatigue (for example, it can't be explained by other conditions) and if you have other symptoms too, such as sleeping problems or problems thinking and concentrating.

The diagnosis can then be confirmed if these symptoms are experienced for several months.

Read more about diagnosing CFS.

How it is treated

There is no cure for CFS, so treatment aims to reduce the symptoms. Everyone with CFS responds to treatment differently, so your treatment plan will be tailored to you.

Some of the main treatments include:

Treatments such as these can help improve CFS in most cases, although some people do not make a full recovery. It is also likely there will be periods when symptoms get better or worse.

Read more about treating CFS.

Chronic fatigue syndrome (CFS)

Dr Charles Shepherd, medical adviser to the ME Association, and who has ME, describes the symptoms, diagnosis and treatments for ME, also known as chronic fatigue syndrome.

Media last reviewed: 19/03/2013

Next review due: 19/03/2015

CFS or ME?

There is some debate over whether the term chronic fatigue syndrome (CFS) or myalgic encephalomyelitis (ME) should be used.

Chronic fatigue syndrome (CFS) is the term often used and preferred by doctors because there is little evidence of brain and spinal cord inflammation, as the term ME suggests. ME is also thought to be too specific to cover all the symptoms.

Myalgic encephalomyelitis (ME) is the term preferred by some people who feel that CFS is too general and does not reflect the severity and different types of fatigue. It also highlights the fact that fatigue is not the only symptom.

Page last reviewed: 20/03/2013

Next review due: 20/03/2015