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have been devoted to the subject and the picture changes almost weekly. Those who suffer from the illness often have passionate views about its origins and anyone who gainsays them is asking for trouble.

      The debate about chronic fatigue syndrome is relevant here because it exemplifies the false dichotomy between ‘psychological’ and ‘physical’ origins of illness. Throughout the controversy runs a seductively misleading vein: the implicit assumption that the illness must be either physical or psychological in origin. But first, what exactly is chronic fatigue syndrome?

      Since 1988 the term chronic fatigue syndrome (CFS) has been used to describe a debilitating illness of unknown origin that has persisted for at least six months. As you probably know (for it is often in the news) CFS is characterized by a dreadful, disabling tiredness that is made worse by any physical exertion. This fatigue is accompanied by a motley assortment of other symptoms, including general malaise, intermittent fevers, pains in the joints, stiffness, night sweats, sore throats, poor co-ordination, visual problems, skin lesions and sleep disorders.

      As if that were not enough, many CFS sufferers also experience psychological problems such as severe depression, forgetfulness, poor attention and lack of concentration. CFS can persist for years and it ruins the lives of those afflicted. Often they will be forced to give up work. Sufferers may show a measure of improvement over time, but the majority remain unwell for several years.

      Cases of CFS have been reported in most industrialized nations including Britain, the USA, Canada, France, Spain, Israel and Australia. Sufferers tend to be young adults between twenty and fifty, though children can also be affected. According to the American Centers For Disease Control and Prevention, more than 80 per cent of CFS sufferers are women, most are white and their average age when the illness develops is thirty. Another common factor is that sufferers usually report having contracted some form of viral infection not long before the syndrome manifested itself.

      As yet, no one has come up with a truly effective remedy for CFS. None of the drugs that have been used to treat the syndrome is of proven effectiveness and some may do more harm than good.

      CFS, as currently defined, is a relatively recent phenomenon. (But then, so is AIDS; the fact that a disorder has only recently been recognized and defined does not detract from its reality.) Records of vaguely CFS-like syndromes, involving severe fatigue, muscle pains and other symptoms, date back at least two centuries. The medical history books, however, contain nothing that can be unequivocally compared with CFS before the second half of the nineteenth century, when neurasthenia became a common diagnosis. Incidentally, cultural stereotypes about the sort of person who was susceptible to neurasthenia were as strong in the nineteenth century as they are now about CFS. Neurasthenia was said to be a disease of affluent middle-class women, in much the same way that CFS has been inaccurately portrayed by the popular media as ‘yuppie ’flu’, a disease of affluent thirtysomething professionals.

      It was not until the first half of the twentieth century that reports of a disorder corresponding to CFS started to accumulate. The first well-documented outbreak of a CFS-like disorder occurred in the 1930s in the USA and was attributed to a mystery virus. A similar mystery ailment afflicted the staff of a London hospital in 1955, in what became known as the Royal Free epidemic. The sufferers experienced persistent muscle pain and fatigue. To begin with the syndrome was referred to as benign myalgic encephalomyelitis. By 1956, however, it had proved to be anything but benign, and so it became known simply as myalgic encephalomyelitis, or ME.

      Since they first appeared on the medical map, CFS-like illnesses have gone by a baffling variety of names including epidemic neuromyasthenia, neurasthenia, Iceland disease, Royal Free disease, atypical poliomyelitis, fibrositis, fibromyalgia, post-infectious neuromyasthenia, post-viral fatigue syndrome and myalgic encephalomyelitis. It is not certain that all these illnesses have been identical with what is now referred to as chronic fatigue syndrome. An analysis of twelve well-documented outbreaks of CFS-like disorders found they differed in various respects, notably with regard to neurological problems.

      Now we come to the real meat of the problem. No one yet knows for certain what causes CFS. The arguments continue to rage and there are major divisions of opinion within the medical community. But what characterizes the whole debate – especially as it is portrayed in the popular media – is the implicit distinction between physical causes, which are held to be genuine, and psychological causes, which are held to be suspect.

      With a few honourable exceptions, expert opinion on CFS divides neatly into two opposing camps. In one camp are those who maintain that CFS has a physical cause such as a virus or an immunological disorder. According to this view, the depression and other psychological symptoms that characterize CFS are consequences rather than causes of the underlying physical disorder.

      In the opposing camp are those who argue instead that CFS is fundamentally a psychological disorder. According to this view, the physical symptoms such as exhaustion, muscle pains, fever and malaise, are manifestations of an underlying psychiatric problem.

      Which view is correct? You may not be surprised to find that both are at least partially true. Many CFS sufferers have symptoms that match the diagnostic criteria for psychiatric disorders and organic disease. The evidence is undoubtedly complex and equivocal but it points towards one conclusion: that chronic fatigue syndrome has both physical and psychological components. Let us examine some of this evidence.

      Most cases of CFS are preceded by a viral infection of one kind or another, and there have been repeated suggestions that a virus might lie at the root of the syndrome. For a long time the prime candidate was the Epstein-Barr virus, a member of the herpes virus family which is also responsible for glandular fever. During the 1980s chronic fatigue syndrome was widely referred to as ‘chronic Epstein-Barr virus infection’, as though its viral origins had been firmly established. Other candidates have included retroviruses (of which HIV is an example) and polio-like viruses called enteroviruses.

      There is as yet no conclusive evidence to support the viral theory and it has therefore fallen out of favour. But even if viruses are not the prime cause of CFS, it remains highly plausible that a viral infection might help to trigger or precipitate the syndrome when other causal factors are also present.

      Several other physical causes besides viruses have been proposed. One theory maintains that the primary symptoms of CFS are produced by hyperventilation – that is, abnormally rapid breathing. The evidence, however, is once again scant. Only a minority of CFS sufferers hyperventilate. On another tack, research at Johns Hopkins University in Baltimore has indicated that certain types of chronic fatigue (though not necessarily all cases of CFS) might result from abnormally low blood pressure. Yet another suggestion has been that CFS stems from a form of neurobiological disorder. One study revealed that more than a quarter of CFS patients had abnormal brain scans, and subtle changes have been found in the levels of neurotransmitter substances in the brain.

      At present, the most favoured physical theories about the origins of CFS revolve around the immune system. There is growing support for the view that the symptoms of CFS result from a perturbation or abnormality in the sufferer’s immune system. This immunological malfunction, it is argued, may be triggered by a viral infection which somehow throws the immune system out of kilter.

      Evidence that CFS involves an immunological disorder is accumulating rapidly. Within the past few years various abnormalities have been found in the immune systems of CFS sufferers. These include alterations in the activity and surface structure of two important types of white blood cells: the natural killer cells and T-lymphocytes. (You will be hearing much more about these cells in later chapters.) It is becoming increasingly evident that CFS is associated with, if not directly caused by, a persistent, low-level activation of the immune system.

      If CFS really is an immunological disorder then why do some perfectly sensible scientists and physicians persist in regarding it as primarily a psychological disorder? They persist because there is highly respectable evidence to support their viewpoint as well.

      Several of the symptoms associated with CFS are also seen in psychiatric illnesses, notably depressive and anxiety disorders. A substantial proportion of those who seek medical help for chronic fatigue turn out to have

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