The disease, if that is what it is, has claimed prominent figures including the Duchess of Kent, who declared herself a victim last December; Esther Rantzen's daughter; and Clare Francis, the former round-the-world yachtswoman, who has since worked tirelessly to publicise it.
Chronic fatigue syndrome is a portmanteau term used by doctors to describe a condition, the cause of which is not understood. It is defined as severe disabling fatigue lasting at least six months made worse by physical or mental exertion and for which no adequate medical explanation can be found. Up to 2.5 per cent of the population - over one million people - are believed to be affected by it.
Once named "yuppie flu", but since dropped as both derogatory and inaccurate as all social classes are affected, it has been variously called Persistent Virus Disease and myalgic encephalomyelitis (ME). Patients' groups, such as the ME Association, claim organic factors - possibly a virus - play an important role, because in many cases the condition develops following a viral illness. However, many doctors believe the causes to be primarily psychological.
To resolve the dispute, the Royal Colleges of Physicians, Psychiatrists and General Practitioners established a working party to examine the issue. In a report last October they sought to bridge the gap between the opposing camps by declaring that the condition could not be considered as primarily physical or psychological but had aspects of both.
Patient groups, including the ME Association and Action for ME, criticised the report for being biased towards psychiatric factors. But they welcomed the recognition that it was a seriously debilitating condition that was poorly understood and poorly managed by doctors.
Professor Simon Wessley, a psychiatrist at King's College Hospital, London, said research was now focusing on why some people were vulnerable to the condition. Four research groups in the UK studying brain function had found the same pattern of low levels of the stress hormone, cortisol, and increased serotonin function. This was a mirror image of depression, characterised by high levels of cortisol and decreased serotonin. "It suggests chronic fatigue syndrome is related to, but not the same as, depression."