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What is it?

Extreme, debilitating exhaustion is the hallmark of chronic fatigue syndrome (CFS). Those who have CFS sleep poorly and awake unrefreshed. They frequently have headaches, muscle and joint pain, sore throats, and problems concentrating and remembering things. The intensity and type of symptoms can vary from day to day. On a “good day” symptoms may be mild and someone with CFS may be able to function at a near normal level, but on a ‘bad day’ they may be unable to get out of bed.

Once dismissed as ‘yuppie flu’ – a form of depression, stress and burnout in young, upper society white women – CFS is now known to exist worldwide in every age, race, and in both sexes. It is about 1.5 times more common in women than in men and appears to be most prevalent in the 20 to 40 year age range. It is estimated that as many as 500,000 people in the U.S. may have CFS. It appears that the incidence of new cases of chronic fatigue is declining in Australia.

The weariness, pain, and numerous other symptoms that are associated with chronic fatigue syndrome can frustrate both patient and physician. They often make the patient miserable, but they do not cause visible, measurable abnormalities. This has lead to lingering scepticism over the existence of CFS despite the fact that all major health organisations now recognise it as a distinct condition. Some doctors attribute the symptoms their patients have to depression or stress, or feel that they are simply symptoms of another, as of yet undiagnosed, disease or disorder. While it is true that some of those with CFS are depressed, many are not. The incidence of depression is about the same as with any other chronic illness.

There are a large number of diseases, disorders, and temporary conditions that can cause (or have as a symptom or side effect) short or long-term fatigue. These may include hypothyroidism, mononucleosis, psychological disorders, eating disorders, cancer, autoimmune disease, infections, drug or alcohol abuse, reactions to prescription medications, and – for whatever reason – not getting enough hours of uninterrupted sleep. In these cases there will be an underlying reason for the fatigue that can be established, and treated. This temporary, short-term, or long-term fatigue is not the same as CFS but it must be distinguished from it. Very few illnesses cause just fatigue.

The problem that researchers, doctors, and patients face in identifying and diagnosing CFS is that the cause of CFS is unknown. For many years, it was simply defined as an idiopathic chronic fatigue (fatigue of unknown origin). In the late 1980’s the US Centers for Disease Control and Prevention (CDC), in conjunction with an international panel of CFS research experts, adopted a definition of CFS (that was reviewed and updated in 1994).

According to this definition, a person with CFS needs to have:

  1. Severe chronic fatigue of six months or longer duration with other known medical conditions excluded by clinical diagnosis
  2. Concurrently have four or more of the following symptoms:
  • substantial impairment in short-term memory or concentration
  • sore throat
  • tender lymph nodes
  • muscle pain
  • multi-joint pain without swelling or redness
  • headaches of a new type, pattern or severity
  • unrefreshing sleep
  • post-exertional malaise lasting more than 24 hours.

These symptoms must have persisted or recurred during six or more consecutive months of illness and must not have predated the fatigue.

While this definition has been widely accepted and is used by researchers and physicians to both study and diagnose CFS, there is still no consensus as to the cause of CFS.

There are many researchers who believe that chronic fatigue syndrome is caused by or triggered by a viral infection, but no microorganism has been isolated as the instigator. Some still believe that an infection, trauma, stress, or allergy provokes a chronic immune reaction and that it is this immune reaction that causes CFS, though this is not widely accepted. Still others think that the central nervous system plays an important role and that hormone regulation is involved.

Some researchers think that CFS’s symptoms may be due to or exacerbated by depression, by neurally mediated hypotension (problems with blood pressure regulation), or due to disturbances that affect the quality and depth of sleep that an affected person gets. While the majority agrees that CFS is not contagious, the tendency to be predisposed may be inherited as family patterns of CFS have been observed. Some investigators feel that further research will reveal that CFS is not a single condition at all but a group of different disorders with a similar end point.

It is known that those affected by CFS have a definite start to their symptoms, a time before which they felt well and had the energy for normal daily tasks. About 75% of the time, CFS is preceded by what appears to be a flu-like illness. Other cases of CFS arise following a period of intense physical or emotional stress, and some emerge slowly with patients noticing a gradual decline in their energy and sense of well-being.


Last Review Date: April 1, 2018