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Thursday, August 7th, 2003

A Definition of Disease

Timothy Wilken, MD

Since the beginning of medicine, physicians have sought an understanding of the cause and definition of disease. They have not been very successful in finding either. A book entitled Theories and Philosophies of Medicine, published in 1973, has a chapter entitled, “Disease—An Undefined Word”. In this chapter, the authors list 39 different definitions of disease used in the history of medicine. These 39 definitions cover the entire gamut of man’s experience. None of these definitions are satisfactory from a scientific viewpoint. I will present two of the definitions that are still in widespread use today. These definitions are presently being taught to the medical students of the western world.

DORLAND’S MEDICAL DICTIONARY defines disease as: “In general, any departure from a state of health, or an illness, or a sickness. More specifically, a definite morbid process having a characteristic train of symptoms. It may affect the whole body or any of its parts and its etiology, pathology, and prognosis may be known or unknown.”

STEDMAN’S MEDICAL DICTIONARY describes disease thusly, “Morbus, illness, sickness. An interruption or perversion of functions of any of the organs, a morbid change of any of the tissues or an abnormal state of the body as a whole, continuing for a longer or shorter period.”

These two definitions both fail to meet the criteria of an operational definition. They suffer from what in science is called circular logic and in fact are of little value. Dr. Selye does not explicitly define disease in his classic work THE STRESS OF LIFE published in 1976; however, he states his preference for a definition from a much less popular medical dictionary called BLAKISTON’S NEW GOULD MEDICAL DICTIONARY.

BLAKISTON DEFINES DISEASE AS FOLLOWS: “The failure of the adaptive mechanism of an organism to counteract adequately the stimuli or stressors to which it is subject, resulting in a disturbance in function or structure of any part, organ, or system of the body.”

This definition of disease is not circular and is presently the best definition available to western medicine. Any general theory of health will require an explicit operational definition of disease. That definition will need to be as absolute as the definitions we use in classical physics.

The Nature of Stressors

Dr. Hans Selye discusses the definition of Stress at length in many writings. His simplest and most generally accepted definition is: “The non-specific response of the body to any demand.” Selye further defines stressor as: “that which produces stress.”

In view of the mind-body unification, we can define stressor as follows:


This expanded definition of stressor is broader and includes things not normally considered to be stressors. This definition allows to divide stressors into two general classes—external and internal stressors. The external stressors can be further divided into three types—physical stressors, biological stressors, and social stressors.

Physical Stressors—The physical stressors are any physical demand made on the mind-body to adapt. They include heat, cold ionizing radiation, chemicals, poisons, toxins, fire, electricity, and trauma of any type.

Biological Stressors—The biological stressors are any biological demand made on the mind-body to adapt. These are primarily adversary living systems which adapt by attacking and exploiting the mind-body. They may be simple or complex. Examples include viruses, bacteria, rickettsia, fungi, parasites, and predators.

Social Stressors—The social stressors are any social demands made on the mind-body to adapt. Social stressors are of two types: coercive and non-coercive. The coercive social stressors are non-voluntary demands made upon the mind-body to adapt. This would include assault, murder, rape, theft, arson, and any crime against an individual and his property. Another example of the coercive social stressors are the non-voluntary demands made by any form of political government such as taxation, regulation, restriction, and incarceration. This would further include all social stressors produced by action of the political government—i.e. war, inflation, recession, injustice, et cetera.

The non-coercive social stressors are voluntary demands made on the mind-body to adapt. They include all voluntary contractual demand relate to marriage, employee/employer relationships, personal friendships, purchase contracts, financial loans, et cetera. The non-coercive social stressors also include the positive stressors for humankind, These are the demands we place on ourselves to achieve our goals and build our civilization. So, some stressors are good for us.

Internal Stressors—The internal stressors are produced by maladaptation of the mind-body. They are the result of errors of stressor adaptability (the ability of the mind-body to adapt to stressors). The most common internal stressors encountered in humans are the maladaptive negative emotions. For this discussion, I propose to use a definition of a human emotion modified after, and expanded from, the operational definition of a human emotion by Dr. David Graham of the University of Wisconsin:

Human Emotion—”A human emotion is the internal, physiological sensation (i.e., gut feeling or inner urges to act) that a human experiences in anticipation and adaptation to stressors. These sensations are the result of the release of powerful adaptive hormones and physiological change that occur throughout the mind-body in preparation for adaptation.”

If a human emotion is appropriate to the provocative stressor, then the emotion serves as part of the mind-body’s stressor adaptability. However, if the emotion is inappropriate, then that emotion becomes an internal stressor for the mind-body. Anger is the emotion that accompanies the mind-body’s preparation to fight. If an individual becomes angry when attacked by a mugger, the individual’s ability to fight off the mugger is improved, and, therefore, the anger is part of the individual’s stressor adaptability. However, if a mother becomes angry with her two-year old child, her anger interferes with her ability to rationally communicate with her child. Since it would be irrational for the mother to want to fight her two-year old chid, her anger acts as an internal stressor for her and her actions as an external stressor for the child.

Other examples of errors of stressor adaptability which produce internal stressor would include auto-immune phenomena (when the immune system of a living system loses its ability to recognize self and attacks its own cells and tissues) and cancer (when a cell type loses its identity with the living system and begins functioning like an adversary living system reproducing itself and parasitizing the living system for which it originated).

Our expansion of the concept of stressors to include physical, biological, volitional, and internal stressors results in a major simplification and an important step toward the understanding of all disease.

The Stressor Hypothesis of Disease Propagation

Disease results within a living system whenever the system’s stressor adaptability (the total ability of the living system to adapt to stressors) is exceeded by the sum of the stressors acting upon the system.

Disease————> when (sa – s) < 0

(where sa represents stressor adaptability and s represents stressors)

A New Concept of Stress and Disease

Disease, from the stressor Hypothesis of Disease Propagation, results within a living system when the sum of stressors acting upon that living system exceeds the system’s ability to adapt. Disease further results in any living system wherein the order within the system is decreasing, or the disorder within the system is increasing. Disease may be localized or generalized, and can affect part of the living system or the entire living system. Disease can affect any level of organization within a living system—cellular, tissue, organ, or organism as a whole. The Stressor Hypothesis of Disease Propagation leads to a more satisfactory definition of stress within living system. This definition of stress is patterned after the classical definition of stress from physics. Stress in physics is defined as follows:

If a steel wire is put under tension, then:

(physical stress) S p = F/A

(force along the wire) divided by (the cross-section area of the wire)

For living systems, I define stress as follows:

(living system stress) S ls = s / sa

(sum of stressors) divided by (stressor adaptability)

From the above definition of living system stress, it follows that disease can be said to exist in any living system wherein the stress is greater than one (1).

S ls = s / sa > 1

Disease is an evolutionary process, and the concept of living system stress is helpful in staging disease within a living system. I find it useful to define four stages of disease that can exist within the living system as a whole or within any of the levels of organization within the living system. The four stages of disease are defined as follows:

DISTRESS—Stage 1—Distress exists within a living system when the sum of stressors acting upon the living system exceeds the stressor adaptability of the system producing a localized or generalized loss of function. The living system, by using reserves and stored energy, is able to restore function without disability.

DISABILITY—Stage 2—Disability exists within a living system when the sum of stressors acting upon the living system exceeds the stressor adaptability of the system producing a localized or generalized loss of function. The living system is unable to restore function even using reserves and stored energy. This must always include functions considered essential; should include functions considered normal; and when more is know, will include functions thar are considered optimal. When using this definition of disability, it is necessary to state the level of organization with the living system to which the disability refers. Disability, by definition, is reversible.

DAMAGE—Stage 3—Damage exists within a living system when the sum of stressors acting upon the living system exceeds the stressor adaptability of the system producing a non-reversible disability. Damage can exist at any level of organization within the living system or within the living system as a whole. No cure is possible at this stage of disease.

DEATH—Stage 4—Death exists within a living system when the sum of stressors acting upon the living system exceeds the stressor adaptability of the living system producing a loss of ability of the living system to produce negentropy or order. Death is irreversible. Disease is evolutionary—first distress, then disability, then damage, and finally death.

Distress, disability, damage, and death can exist at individual levels of organization within living systems as well as the living system as a whole. The first few stages of disease—distress and disability —are curable. The second two stages of disease—damage and death—are not curable and not reversible. As the science of medicine progresses, disease presently considered damage may be converted to disability by new understanding and technology.

The test of the rightness of any hypothesis lies in corroboration The Stressor Hypothesis of Disease Propagation was formulated over a six-month period, beginning late August of 1978. As a physician providing care for patients on a daily basis, I have had ample opportunity to corroborate the essential features of this Hypothesis. Widespread corroboration and acceptance, of course, can only come after widespread disclosure. The usefulness of any hypothesis depends upon application. I have been applying the Unified Stress Concept to my own life and to the lives of my patients for over two decades now. I am satisfied that such application is of great benefit to me and to my patients. In over twenty years of application, I have found no instances in which the principles are not valid.

Read the complete Unified Stress Concept