Chronic Fatigue Syndrome
Michael Sharpe
Simon Wessely
Introduction
Chronic fatigue syndrome is a controversial condition, conflicts about which have frequently burst out of the medical literature into the popular media. Whilst these controversies may initially seem to be of limited interest to those who do not routinely treat such patients, they also exemplify important current issues in medicine. These issues include the nature of symptom-defined illness; patient power versus medical authority; and the uncomfortable but important issues of psychological iatrogenesis.(1,2) The subject is therefore of relevance to all doctors.
Fatigue as a symptom
Fatigue is a subjective feeling of weariness, lack of energy, and exhaustion. Approximately 20 per cent of the general population report significant and persistent fatigue, although relatively few of these people regard themselves as ill and only a small minority seek a medical opinion. Even so, fatigue is a common clinical presentation in primary care.(2)
Fatigue as an illness: chronic fatigue syndrome
When fatigue becomes chronic and associated with disability it is regarded as an illness. Such a syndrome has been recognized at least since the latter half of the last century. Whilst during the Victorian era patients who went to see doctors with this illness often received a diagnosis of neurasthenia, a condition ascribed to the effect of the stresses of modern life on the human nervous system the popularity of this diagnosis waned and by the mid-twentieth century it was rarely diagnosed (although the diagnosis subsequently became popular in the Far East—see Chapter 5.2.1). Although it is possible that the prevalence of chronic fatigue had waned in the population, it is more likely that patients who presented in this way were being given alternative diagnoses. These were mainly the new psychiatric syndromes of depression and anxiety, but also other labels indicating more direct physical explanations, such as chronic brucellosis, spontaneous hypoglycaemia, and latterly chronic Epstein-Barr virus infection.(2)
As well as these sporadic cases of fatiguing illness, epidemics of similar illnesses have been occasionally reported. One which
occurred among staff at the Royal Free Hospital, London in 1955 gave rise to the term myalgic encephalomyelitis (ME), although it should be emphasized that the nature and symptoms of that outbreak are dissimilar to the majority of those now presenting to general practitioners under the same label.
occurred among staff at the Royal Free Hospital, London in 1955 gave rise to the term myalgic encephalomyelitis (ME), although it should be emphasized that the nature and symptoms of that outbreak are dissimilar to the majority of those now presenting to general practitioners under the same label.
A group of virologists and immunologists proposed the term chronic fatigue syndrome in the late 1980s.(3) This new and aetiologically neutral term was chosen because it was increasingly recognized that many cases of fatigue were often not readily explained either by medical conditions such as Epstein-Barr virus infection or by obvious depression and anxiety disorders. Chronic fatigue syndrome has remained the most commonly used term by researchers. The issue of the name is still not completely resolved however: Neurasthenia remains in the ICD-10 psychiatric classification as a fatigue syndrome unexplained by depressive or anxiety disorder, whilst the equivalent in DSM-IV is undifferentiated somatoform disorder. Myalgic encephalomyelitis or (encephalopathy) is in the neurological section of ICD-10 and is used by some to imply that the illness is neurological as opposed to a psychiatric one. Unfortunately the case descriptions under these different labels make it clear that they all reflect similar symptomatic presentations, adding to confusion. Official UK documents have increasingly adopted the uneasy and probably ultimately unsatisfactory compromise term CFS/ME.(4) In this chapter, we will use the simple term chronic fatigue syndrome (CFS).
Clinical features
Symptoms
Chronic mental and physical fatigue, tiredness, or exhaustion that is typically exacerbated by activity is the core symptom of CFS. Commonly associated symptoms include impaired memory and concentration, muscular and joint pain, unrefreshing sleep, dizziness and breathlessness, headache, tender lymph glands, and sore throat. Patients often describe day-to-day fluctuations in symptoms, irrespective of activity. Periods of almost complete recovery may be followed by relapse, often described as sufficiently severe to make normal daily activity impossible. Depression and anxiety are common, and a proportion of patients suffer panic attacks.
Physical signs
Physical examination is typically unremarkable. Complaints of fever and lymphadenopathy are not confirmed on examination. The presence of definite physical signs (such as objectively measured fever) should not be ascribed to the syndrome and alternative diagnoses should be sought.
Other common characteristics
As well as the symptoms described above patients with CFS commonly have additional clinical characteristics. These are listed in Table 5.2.7.1.
Patients are often worried that remaining active despite fatigue will harm them and consequently avoid activity or oscillate between rest and bursts of activity, which produces fatigue, leading to a return to rest and so on.
Some patients feel strongly that their illness is ‘medical’ rather than ‘psychiatric’ and are particularly concerned that a psychiatric diagnosis implies that the illness is their fault, an indication of personal weakness or even an accusation of malingering. Perfectionist and high achieving lifestyles often with low underlying self-esteem are commonly observed in patients referred to hospital clinics.
Table 5.2.7.1 Common characteristics of patients with CFS | ||||||||
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Although there are no physical signs there may be measurable effects of reduced activity with so-called physiological deconditioning leading to poor tolerance of activity, and in cases where rest has been prolonged other physiological changes such as postural hypotension. Sleep is often unrefreshing and fragmented.
Some patients can become markedly dependent on a carer. Occupational stresses and difficulties are common and it can be difficult to determine if these were contributors to, or are consequence of their illness. Finally many patients have received unhelpful medical attention. Such psychological iatrogenesis includes, on the one hand dismissal of their complaints and on the other over investigation.(5)
Case study
A typical patient is found in the infectious disease department of the general hospital. She is a 30-years-old nurse and her principal complaints are of fatigue, poor concentration, and muscle pain. Her symptoms fluctuate and are made worse by physical and mental exertion. She is no longer able to work and has substantially reduced her daily activities. The history is of an acute onset of symptoms after a ‘viral illness’. Enquiry reveals symptoms suggestive of depression or anxiety, but without obvious mood change. The patient strongly believes the illness to be ‘medical’ rather than ‘psychiatric’.
Classification and diagnosis
There are several published case definitions for CFS. The currently most widely used definition is based on an international consensus of researchers is shown in Table 5.2.7.2.(6) A guide on its application has also been published.(7) It should be remembered that this definition represents nothing more than a working definition of a clinical problem, pending further understanding, and as with most psychiatric diagnoses, does not delineate a single disease.
Issues for a definition of chronic fatigue syndrome
The case definition shown in Table 5.2.7.2 has been useful in unifying the field and providing a widely used operational definition. However, it also has significant limitations.
Table 5.2.7.2 International consensus definition of chronic fatigue syndrome | ||||||||||
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It excludes fatigue associated with known organic disease.
It overlaps with other functional medical diagnoses.
It overlaps with psychiatric diagnosis.
The homogeneity of the patient group it identifies is doubtful.
(a) Differentiation from fatigue associated with organic disease
Fatigue is a common symptom of most medical and psychiatric conditions. CFS refers only to fatigue where there is no clear alternative diagnosis (but does not exclude depression and anxiety unless the depression is of melancholic type or a manifestation of a bipolar disorder). It therefore only refers to idiopathic fatigue. This means that the definition highlights an important clinical problem but also means that the interesting equally important and probably informative phenomenon of fatigue in patients with diseases such as multiple sclerosis is excluded from this definition.
(b) Overlap with other medically unexplained syndromes
A number of medical diagnoses are defined only by symptoms. These functional syndromes are medical diagnoses where there is no identifiable pathology. They include chronic pain, fibromyalgia, and irritable bowel syndrome. Although chronic pain syndromes are principally characterized by pain, fibromyalgia by tender points, and irritable bowel syndrome by symptoms of bowel disturbance, all these syndromes are also associated with chronic fatigue, and patients diagnosed with one of these syndromes often meet the diagnostic criteria for CFS.(8)
(c) Overlap with psychiatric syndromes
Most patients who meet criteria for CFS also fulfil criteria for a psychiatric diagnosis. Many meet criteria for anxiety and depressive disorders and others merit diagnoses of somatoform disorder or neurasthenia. This issue is discussed further below.
(i) Depression
If patients with a depressive disorder are asked about a wide range of somatic symptoms including fatigue and/or muscle pain (which they are usually not) they often report these. If the diagnostic criteria for depressive disorders are applied to patients with fatigue a high proportion meet these.(9) Furthermore the prevalence of major depressive disorder in patients referred to hospital with CFS is substantially higher than in patients with chronic disabling medical diseases suggesting that depression is not simply a reaction to disability.(10) In practice, the diagnosis of depression can be difficult in patients presenting with fatigue: depressed mood is often not prominent and anhedonia can be hard to distinguish from the inability to pursue previously enjoyed activities because of fatigue. Finally, whilst there is a strong association between major depressive disorder and CFS, for as many as half of the patients seen in hospital clinics the symptoms cannot be readily given that diagnosis.
(ii) Anxiety disorders
Although less attention has been given to the association between fatigue and anxiety, an examination of diagnostic criteria for anxiety disorders reveals that the typical somatic symptoms of anxiety include fatigue and other symptoms listed as typical of CFS. If sought, generalized anxiety disorder can often be diagnosed in patients with CFS and panic can often be diagnosed in patients with severe episodic symptoms.(11) As with depression, however, anxious mood is rarely obvious and may be hard to distinguish from reasonable concern about consequences of being ill. Likewise, true phobic avoidance may be hard to distinguish from the consequences of fatigue and/or weakness.
(iii) Neurasthenia
ICD-10 differs from DSM-IV in including this diagnosis. It requires that the patient suffers from fatigue which is exacerbated by exertion, as well as several other somatic symptoms, and does not meet the criteria for a depressive or anxiety disorder (see Chapter 5.2.10). One study found that almost all of the referrals to a medical CFS clinic met the criteria for neurasthenia as defined by ICD-10.(12)
(iv) Somatoform disorders
According to DSM-IV patients with severe persistent fatigue who do not meet criteria for anxiety or depressive disorders are assigned to a somatoform disorder diagnosis. These are a controversial group of psychiatric syndromes characterized by medically unexplained symptoms and of presumed psychological origin.(13) There are a number of subcategories:
Somatization disorder (Briquet’s syndrome) is used to describe patients who report multiple, recurrent, medically unexplained symptoms; a minority of patients with CFS will meet the criteria for this disorder.
Hypochondriasis describes a syndrome in which the patient’s main concern is with the possibility that they are suffering from an organic disease. Whilst this diagnosis would seem to be applicable to many patients with CFS, it is problematic when the cause of the illness in question, which is regarded as uncertain by doctors as well as patients.
Almost all patients with CFS not meeting the criteria for any of the above DSM disorders are likely to fall into the undemanding residual category in DSM-IV of ‘undifferentiated somatoform disorder’. This diagnosis is of dubious practical use, and in effect merely confirms that the patient has multiple physical symptoms of unclear aetiology.
(v) Conclusion
Many patients with CFS meet the diagnostic criteria for a depressive or anxiety disorder, although in practice the presentation is often ‘atypical’. It is likely that patients who do not meet the criteria for either of these could be diagnosed as having either neurasthenia (ICD-10) or undifferentiated somatoform disorder (DSM-IV).
Should we use the diagnosis of CFS?
From the psychiatrist’s perspective it is parsimonious to ask whether a diagnosis of CFS is ever necessary or appropriate when the symptoms can always be described by a psychiatric diagnosis? This unsatisfactory situation is an artefact of parallel medical and psychiatric diagnostic systems for patients with somatic symptoms unexplained by disease. Consequently whether one uses a ‘medical’ diagnosis of CFS or a ‘psychiatric’ diagnosis of somatoform disorder is merely a matter of choice. When making that choice the following must be considered:
A diagnosis of CFS only describes a presenting clinical syndrome, rather than a specific disorder or disease process.
Pragmatically the relative acceptability of the alternative diagnosis to the patient is important. There is no point in giving a diagnosis that is rejected by the patient and impedes any therapeutic relationship and chances of treatment.
One approach to overcoming the issue of parallel classification systems is to combine the medical diagnosis of CFS and the psychiatric diagnoses: According to such a scheme CFS would be subclassified into CFS/depression, CFS/anxiety, and CFS without depression or anxiety disorder (i.e. CFS/somatoform or CFS/neurasthenia). Psychiatric diagnoses that have important clinical utility such as major depressive disorder should obviously be made if present. The usefulness of diagnoses such as undifferentiated somatoform disorder is less clear.
Finally rather than becoming side-tracked by the unanswerable question of whether the patients symptoms are ultimately ‘medical’ or ‘psychiatric’ in nature an open-minded and pragmatic approach is required.
Epidemiology
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