What causes Chronic Fatigue Syndrome?

When it comes to controversy and heated debate, few illnesses come close to Chronic Fatigue Syndrome, also known as Myalgic Encephalomyelitis (ME).

There have been arguments about whether it exists, the cause, the best treatments and even the name itself.

These disagreements have reached the level of abuse and death threats.

The disease itself, however, remains poorly understood - or as one doctor put it: "The whole thing is surrounded by uncertainty".

Does it exist?

For a long time, the existence of CFS/ME was widely dismissed and labelled as "yuppie flu". That opinion has largely been reversed in the past decade.

Continue reading the main storyToo vague, too precise?

Should the illness be called CFS, ME or CFS/ME?

Doctors prefer the term CFS as the main symptom is fatigue, while ME has a specific meaning related to inflammation of the brain and spinal cord.

However, this is not popular with some patients' groups or charities, which talk about ME as a specific disease, saying "fatigue" is too broad a term.

Prof Michael Sharpe, of the University of Oxford, said: "The concepts of CFS and ME have been conflated as CFS/ME. That may be right but it may be a bit like an apple/banana - we need to be clearer what we are talking about."

In 2002, then chief medical officer Prof Sir Liam Donaldson described it as a "disease in the wilderness". He was presenting a report which said CFS/ME was a "genuine illness and imposes a substantial burden on the health of the UK population".

It is thought to affect about a quarter of a million people in the UK.

The main symptom is severe fatigue, made worse by exertion, which does not go away after resting. Muscle pains, headaches, memory problems and depression can also be involved. In some cases it can be completely debilitating, resulting in patients being unable to leave their beds.

Understanding of the disease is largely led by those symptoms. There is no test for CFS/ME, instead it is diagnosed by ruling out other conditions which might produce the same symptoms.

The underlying cause, or indeed causes, have been more elusive.

Uncertain origins

One of the issues in the field is that there is an emerging consensus that CFS/ME is not one illness.