Stands for myalgic encephalitis and chronic fatigue syndrome. It is a condition that is characterized by long-term fatigue and other symptoms that limit a person's ability to carry out ordinary daily activities.

The diagnosis is based on a set of criteria. The fatigue experienced by sufferers is not due to ongoing exertion, is not much relieved by rest and is not due to a previous medical condition. Fatigue is a common symptom of many illnesses but unexplained  fatigue and the severity of functional impairment in CFS is comparatively rare.


While scientists often prescribe cognitive behavioral therapy (CBT) and graded exercise therapy (GET) patients report to worsen from these therapies. CFS, is defined by post exertional malaise (PEM) according to the criteria used by the Institute of Medicine. Most of the studies that show a benefit from CBT and GET used less strict criteria of which PEM was not a requirement. For most true CFS patients who's conditions are defined by PEM, GET is damaging.

The PACE study

One clinical trial in particular is notorious for its design flaws. The PACE-study had to adjust its outcome measure to be able to report improvement. They reported that 22% of patients were cured and 60% improved from CBT and GET. To come to these conclusions the PACE authors had altered the way in which they measured improvement and recovery to increase the apparent benefit of the therapies.

Some scientists have been critical towards researchers in the psych-based fields. They suggest that sometimes they are trying to find psychological explanations for illness that then might be treated with psychological interventions; not in a search and find but in a find what we search for kind of fashion.

The link with Lyme disease

Because patients with CFS have similar clinical symptoms as Lyme disease patients including fatigue, pain, depression, headaches and concentration problems some doctors think that Lyme disease could be the cause of their CFS.

Some patients, initially diagnosed with CFS, are tested years later for Lyme disease, and recover partially after antibiotic therapy. That doesn't mean that all CFS patients suffer from Lyme disease, but because both diseases involve a subjective set of symptoms that can overlap, it is to be mentioned that it is important to rule out Lyme disease before accepting a CFS diagnosis.

It is also to be mentioned that scientists looked at the levels of anti-neural antibodies in CFS patients. These are antibodies that target parts of the brain and can possibly cause auto-immune responses against the brain. Researchers however did not see any reactivity in CFS patients above the healthy controls while in patients with an official Lyme disease diagnosis the levels of anti-neural antibodies was abnormal in comparison to the control group.

This suggests Lyme disease and CFS are two different diseases but that doesn't mean an individual patient gets the wrong diagnosis every now and then.