JMS Pearce, MD

Hull Royal Infirmary, Hull, United Kingdom

       I tried to unveil the stillness of existence through a counteracting murmur of words, and, above all, I confused things with their names: that is belief.

—Jean-Paul Sartre, The Words

Disease implies the converse of health, but even health itself is difficult to define. With the gifts of technology the practice of medicine has changed radically from a patient–based, thorough history and examination to a mechanistic, technological service that too often bypasses human contact. With this transformation, the carefully considered, accurate naming of an illness has fallen into abeyance at the divergent altars both of sophisticated technical description and loosely conceived labels.1 Both communication and precise nomenclature are hampered.

The media have been quick to latch onto these labels. Unqualified opinions proliferate, providing validity to diagnoses and diseases of questionable origin. Imprecise use of terminology is a matter of major concern. It falsely implies an understanding while commonly overlooking the separation of illness from normal variants of physiological symptoms. In such a manner, symptoms and syndromes of obscure causation can be mistaken for valid diseases, and subjective complaints are medicalized in order to justify them as social and occupational disabilities. Imprecise use of terminology is of major concern as it falsely implies an understanding, which stultifies scientific research and is conducive neither to sensible diagnostic processes nor constructive management of the patient. As the former editor of the British Medical Journal noted, there is an “increasing tendency to classify people's problems as diseases.” 2


Concepts of disease are inevitably heterogeneous. What is regarded as a disease also changes at different periods of history because of increasing knowledge, changing expectations, and improvements in diagnostic technology.3 In all cultures, disease represents a deviation from the concept of normal health.4, 5, 6 However, because human diseases relate to people of varied attitudes, expectations, and culture, concepts of disease vary with class, gender, and ethnic group. Diverse social reward and economic factors also change the idea of illness and its sequelae.7

The interface of health, disease, and illness has also puzzled many disciplines, including medicine, history, anthropology, health sociology, public health, and significantly, philosophy and theology. Although methods for describing a disease vary across disciplines, it is necessary to use names for sensible communication. Medical semantics dictate that disease names progress, in general, towards causation. As disease names are refined, syndromic terms are replaced by names for disorders of structure or function, with the ultimate aim being a specific, identifiable defining mechanism, which then replaces broader syndromic descriptions.

Disease emerges as an important but subjective concept, often involving a series of value judgments. Physicians rightly tend to insist on objective manifestations or deviations of measurable values from the norm: the so-called Normativism definition; the layman by contrast often believes that disease (“He’s got flu.”) or health are empirical facts and nothing more: Non-normativism.7 Diseases are frequently mistaken for diagnoses: both terms demand accurate definition to avoid clinical errors.

Definitions of disease. Originally, from 14th century Middle English, a disease was a condition of the body, or of some part or organ of the body, in which its functions were disturbed or deranged, “a departure from the state of health, especially when caused by structural change.” Its present meaning appeared in the 15th century as “a species of disorder or ailment, exhibiting special symptoms or affecting a special organ” (OED). A commonly cited but unattributed definition is: “A change produced in living things in consequence of which they are no longer in harmony with their environment.”1

With the emergence of modern diagnostics, this definition of disease is too broad and imprecise to be of utility. The foundations of definition also vary widely. Some highlight a more nominative, confining approach that excludes all conditions in which a specific cause is not known, “A disease is any disturbance or anomaly in the normal functioning of the body that probably has a specific cause and identifiable symptoms.”8 Yet another view seeks to define disease by its perceived function: “What we call a disease is the defensive reaction of our body’s mechanisms designed to maintain us healthy.”9

JG Scadding with scholarly perception considered many disparate concepts in contributing his own general, biological definition of disease:

In medical discourse, the name of a disease refers to the sum of the abnormal phenomena displayed by a group of living organisms in association with a specified common characteristic or set of characteristics by which they differ from the norm of their species in such a way as to place them at a biological disadvantage.10

With all of the varying definitions, no universally accepted criteria establish what is or is not a disease. Diseases are often defined by a common feature that characterizes the group of symptoms on which a disease’s description is based. Definitions may therefore be: descriptive or syndromal, morbid-anatomical, pathophysiological, and etiological. As knowledge advances, the syndrome tends to be displaced when definition by more objective features (e.g., etiology) takes precedence.10 The different practice of making diagnoses is a utilitarian way in which physicians work.

Technology and disease. Many years ago Boorse stressed the exclusion of subjective judgments in the description of health and disease, confining their definitions to statistical norms.11 In an extension of this notion, Hoffman argues that:

Technology provides the physiological, biochemical, and biomolecular entities that are applied in defining diseases. Technology can constitute the defining signs, markers, and end points as well as medical taxonomy. It establishes how we act towards disease: thorough technology establishes diagnosis and treatment: the actions that constitute the concept of disease.3

However, there are many conditions where there are no technological tests. Whiplash syndromes and fibromyalgia have no corresponding technological tests. The advocates of the technological concept see these examples “as borderline cases and classified as syndromes. Non-technological disease entities [sic] are low-status diseases, precisely because they are not technologically testable and treatable.”12 However, this simplified mechanistic view notably disregards the essential, albeit subjective, human aspects of disease.


Diagnosis is the ascription of a name to an illness, though the word illness itself evades precise definition. Diagnosis derives from the Greek διαγigνωσkeιn to distinguish or discern. It implies the distinction of illness or disease from health. The accurate formulation of diagnosis connects a disease to its sequelae and may indicate the correct treatment and prognosis. It comprises three stages or levels: first, the category or class of disorder, providing a broad frame of reference (e.g., neuromuscular disorder); second, the subject to be diagnosed (e.g., 30-year-old female); and finally a more specific categorization (auto-immune myasthenia gravis).13 An old but comprehensive account stated:

Diagnosis consists in bestowing a name upon a certain assemblage of pathological phenomena . . . which includes a knowledge of the causal factors of the disease; a determination of its character with reference to type and severity; an estimate of the amount and kind of damage, both general and local, which has been sustained by the organism; a forecast of the probable course and duration of the morbidity process; and a cognizance of the personal characteristics of the patient, whether psychic or physical, inherited or acquired.14

The primary object of diagnosis is successful treatment and prognosis. Diagnosis may be applied to (a) a described and recognizable combination of symptoms and signs (e.g., headache and vomiting); (b) phenomena associated with a specified pathology or disorder of function such as raised intracranial pressure; (c) a specific cause or causes such as brain tumor or hematoma. However, a diagnosis does not include every potential symptom of a disease. Sir Thomas Clifford Allbutt clarified the issue over 100 years ago:

Clinical diagnosis, however, is not investigation—a distinction some practitioners forget; diagnosis depends not upon all facts, but upon crucial facts. Indeed we may go farther and say that accumulation of facts is not science; science is our conception of the facts: the act of judgment, perhaps of imagination, by which we connect the unknown with the known.15

As in Hughlings Jackson’s Spencerian notion of hierarchical levels, the strength of a diagnosis should increase from non-specific symptoms to exact causation. Hierarchical levels of a diagnostic category should be clearly identifiable since commonly employed diagnostic criteria may have been confounded with disease symptoms.

Confusion arises when different people use different defining criteria, and when diagnosis is wrongly equated with disease, which as a rule is more vaguely defined. This leads to problems in discussions especially of disorders of uncertain or multifactorial cause, such as asthma, migraine, fibromyalgia, chronic fatigue syndrome, post-traumatic stress disorder, and attention deficit disorder.

The fallacies of equating a diagnostic label with a disease are nowhere more problematic than in psychiatry16 where objective phenomena are sparse. Schizophrenia has been regarded as a psychosis, a disease of the mind, but recent work has shown unequivocally physical abnormalities in brain imaging and blood flow which make it clear that though the etiology(ies) is unknown, an organic syndrome is present. Similar arguments may apply to endogenous bipolar depression and to many pain syndromes of uncertain cause.

In other instances, conditions of uncertain etiology are relabeled to include a variety of symptoms not previously associated with the illness. Post-traumatic stress disorder (PTSD) is one such example of an old disorder disguised as a “new syndrome." Originally known as “shell shock,” the symptoms of this disorder were derived from a war veteran’s response to acute, massive psychological stress of life-threatening severity (e.g., a comrade blown to pieces stepping on a mine, seeing a friend or relative consumed by flames); shell shock also included an individual’s response to a similar situation in civilian life (e.g., witnessing someone crushed by a falling building or killed by a car). However, the label PTSD has now been extended to less severe experiences so that uninjured relatives, accident witnesses, or victims of minor car accidents claim the disorder, often in the context of pending litigation.

The problem with syndromes. As illustrated, the disease-diagnosis distinction becomes particularly murky with regards to the syndrome—a type of disease whose identification depends on identification of a list of possible combinations of signs and symptoms displayed by a patient within a specified time. While low on the diagnostic hierarchy, clearly delineated syndromes are valuable labels for communication. But without specific criteria, they do not constitute a disease. Syndromes can be a fertile field for hastily considered ideas and spurious labels.

When a syndrome that lacks concrete criteria is widely recognized as a diagnosis in both medical and lay articles, including the popular media, it acquires both social acceptability17 and a false notion that it is an actual disease (e.g., PTSD or fibromyalgia). New clinical diagnostic labels are often welcomed primarily as opportunities for market growth of drugs and other questionable treatments.18 But more importantly, popular belief in such vague diagnoses does not tend to disperse under the light of further scientific inquiry. The greatest scientific virtue is the willingness to recognize a theory's refutation. Only if this tenet is observed will advances in knowledge diminish or abolish specious labels posing as definitive diagnoses or diseases.

Issues of nomenclature: essentialist or nominalist?

Medical and non-medical people apply differing philosophies to the conception of disease and diagnosis. In the nominalist approach a disease or diagnosis is located in the individual. The nature or substance is decided by reference to a biomedical norm, and the names are convenient devices by which the diagnostic process can be stated briefly. Essentialism is based on the Aristotelian notion that natural organisms show an invariant general pattern or essence shared by all members of the group.19 Nominalist definitions do not attempt the impossible task of assessing the essence of a disease, but rather describe how a disease relates to observable phenomena in individuals. The philosopher, Karl Popper20 pointed out that essentialist definitions, depending upon intuitive acceptance for their validity, have no place in science. Thus, terminology of disease in medical discourse in effect necessitates nominalist definition.19

Many symptom-complexes also masquerade behind labels that feign concrete etiology: the late whiplash, fibromyalgia, chronic temporomandibular syndrome, repetitive strain injury, multiple chemical sensitivities, sick building, and Gulf War syndromes. The instinctive quest for a physical cause is evident in their names, even though the etiology is unknown. For instance, Victorian doctors viewed fatigue as both a physical and mental affliction.21 Neurasthenia (a word with the merits of simplicity and its self-evident meaning) was a descriptive term coined by George Miller Beard22 for the colloquially known nervous exhaustion—commonplace in the 19th century. While neurasthenia as a diagnosis declined between the 1930s and 1960s, it re-emerged in the 1980s as chronic fatigue syndrome.23 This had “adopted the organic inheritance of Beard's ideas of neurasthenia, despite the fact that the question of organicity could not be decisively answered in a single case.”24

"Each civilisation," wrote Ivan Illich, "defines its own diseases. What is sickness in one might be chromosomal abnormality, crime, holiness, or sin in another."25 Smith noted the practical social consequences of diagnosis commenting: “To have your condition labeled as a disease may bring considerable benefit both material (financial) and emotional. However, the diagnosis of a disease may also create problems; you may be denied insurance, a mortgage, and employment.”2

Until the etiology of a complaint is determined, medical terminology is by necessity imprecise. For practical purposes, such terminology facilitates communication, but that does not justify the medicalization of non-specific aggregations of symptoms, which describe common human complaints rather than diseases. In practice, research investigations and treatment require decisions that are based on value judgments—necessitating the use of subjective descriptive elements on the part of both patient and physician. However, where possible, we should eschew loosely formulated diagnostic labels and value judgments. “Better,” argued Clifton Meador, “to describe a patient in whom a diagnosis could not be made as having a ‘non-disease’ than make the common error of continuing to label such patients with non-existent diseases."26

There are no conflicting interests or financial support in this work. This paper is based on: Pearce JMS. Disease, diagnosis, or syndrome? Practical Neurology 2011; 11: 91–97.


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JMS PEARCE, MD, FRCP (London) is emeritus consultant neurologist in the Department of Neurology at the Hull Royal Infirmary, England. All correspondence to: 304 Beverley Road, Anlaby, East Yorkshire, HU10 7BG, England.