Perspectives in Biology and Medicine

A UNIFIED CONCEPT OF HEALTH AND DISEASE GEORGE L. ENGEL, M.D.* In 1951, at the dedication of the Institute for Psychosomatic and Psychiatric Research and Training of the Michael Reese Hospital, I first attempted to formulate a unified concept of health and disease (1). This paper is an extension and to some extent a reformulation ofthat work. I. Unitary Concept ofHealth and Disease versus Unit-Causes Medicine is concerned in the broadest sense with the problems ofhealth and disease and, more specifically, with the mechanisms and the processes whereby health is maintained or disease develops. Health and disease are relative concepts which do not easily lend themselves to simple definition. Romano has proposed the following formulation (2): "Health and disease are not static entities but are phases oflife, dependent at any time on the balance maintained by devices, genically and experientially determined, intent on fulfilling needs and adapting to and mastering stresses as they may arise from within the organism or from without. Health, in a positive sense, consists in the capacity of the organism to maintain a balance in which it may be reasonably free ofundue pain, discomfort, disability or limitation of action, including social capacity." Disease corresponds to failures or disturbancesinthe growth, development, functions, and adjustments ofthe organism as a whole or ofany ofits systems. Clearly, such a definition is too broad to be ofpractical value. Further, it includes value terms—"reasonably free," "failures," "disturbances"—without defining them. Still, it is useful as a starting point since it does not restrict us to any one parameter. It is to be contrasted, for example, to the cellular concept ofdisease, which, by focussing primarily on changes within the cell as the basic component ofdisease, actually restricted attention to only one aspect * Departments ofPsychiatry and Medicine, University of Rochester Medical Center, Rochester, New York. This work has been supported in part by a programmatic research grant from the Ford Foundation to the Department ofPsychiatry. 459 ofdisease—and one which is not necessarily present. It tries to get away from the implicit assumption that disease is a thing in itself, unrelated to the patient, the patient's personality, bodily constitution, and mode oflife —a concept ofantiquity which repeatedly reasserts itselfeven in our language , as when we say that a patient has a disease or that we treat a disease (3). The broad definition ofdisease does not confine our attention to any single system of organization ofthe body. It permits us to conceptualize disturbances or failures at all levels oforganization—biochemical, cellular, organ, psychological, interpersonal, or social—and to consider their interrelationships . Further, it does not restrict us to any single etiologic concept but permits the application ofa multi-factor concept. An important aspect ofmany concepts ofdisease has been the tendency to ascribe disease to a "bad" influence, usually something external which gets into the body. This theme characterizes most primitive and prescientific views of disease and has reappeared repeatedly in various guises in the scientific era. To be able to think ofdisease as an entity, separate from man and caused by an identifiable substance, apparently has great appeal to the human mind. Perhaps the persistence ofsuch views in medicine reflects the operation of psychological processes to protect the physician from the emotional implications ofthe material with which he deals. The material ofmedicine is sick or disturbed man. The physician cannot detach himselffrom his material as the physicist or the botanist can from his. It should not surprise us, then, that concepts which permit some measure of psychological detachment should have unconscious appeal to both physician and patient. The mechanism ofprojecting to the outside what is felt or experiencedas uncomfortable, painful, ordangerousis universal in every human being and is characteristic ofone phase ofthe psychological development ofevery child. So too is the idea that what is felt as bad or painful inside got there from the outside. In prescientific medicine such psychological processes achieved expression in the form of demonologie concepts. Disease resulted from the malevolent influence ofdemons, ancestor or animal spirits, spirits of the dead, the revenge ofghosts, mystical object intrusion, loss ofsoul, taboo violation, sorcery, or witchcraft. A man became ill because he had an enemy who cast a spell or...