The Scientific Usefulness of the Idea of Illness

THE SCIENTIFIC USEFULNESS OF THE IDEA OF ILLNESS HORACIO FABREGA, JR. * An idea of disease is a common feature of cultures and is probably a universal. In a practical sense the idea is useful, since it has served to focus attention on certain types of problems and facilitated ways of understanding and controlling them. Although ofvalue when applied to humans and for practical and social ends, its usefulness in general biology is unclear. In this paper I review how the idea of disease is used to describe happenings which take place in human and in animal groups and point out differences as well as inconsistencies in its meaning. Analysis of this problem area leads me to propose that we really need two ideas, namely, disease and illness. I then illustrate some of the implications of my proposed conventions. Definitional Issues We use the term "disease" frequently and mean by it an impairment in health and well-being [I]. All peoples have ideas of disease roughly analogous in meaning to ours [2, 3]. However, because my purposes have been to explore the theoretical and scientific implications of this idea, I have adopted rigorous definitional criteria: "Disease" refers to a negative (i.e., unwanted) discontinuity or deviation in the condition of a person (4—8). The condition of a person is assessed on the basis of his verbal reports (e.g., pain, body functioning, etc.), the observations of others, and/or by means of various procedures applied to the person. The process of assessment (i.e., diagnosis) involves determining whether a person 's condition deviates, and two types of norms seem to be. used to establish that this deviation is present: norms set by the person across time (i.e., personal norms) and norms set by a relevant group to which the person belongs during the present time period (i.e., group norms). I have indicated elsewhere that from a social standpoint this stipulation ?University of Pittsburgh, 3811 O'Hara Street, Pittsburgh, Pennsylvania 15261.© 1979 by The University of Chicago. 0031-5982/79/2204-0065$01.00 Perspectives in Biology and Medicine ¦ Summer 1979 | 545 constitutes a necessary condition for claiming that someone is diseased. The class of diseased persons of a society is a subset of those classed as deviant [9]. Cultural conventions about well-being and health are used to measure deviations. When preliterate people use the idea of disease, they usually have in mind changes in the (sick) person's behavior and functioning. In modern nations, behavior and functioning are important , but more and more abstract attributes of the person (e.g., physicochemical, anatomical, physiological, etc.) are implied. When the latter attributes are salient, I say that the idea or concept of disease is biomedical. The Concept ofDisease in General Biology Since man is a member of the class of living animals, one would think that the idea of disease would have scientific utility in general biology. However, though the idea is used, its meaning is ambiguous and its explanatory power can be questioned. For example, in the mathematical study of populations, disease and its effects are constantly being considered . Here the idea is used to mean factors, often genetic, which are harmful to the population [10]. The condition of deviations which is central to the use of the concept in human communities seems far removed . Moreover, one can envision states of a population which an evolutionary biologist might describe as involving disease, but which would not meet the condition involving deviations. Thus, members of a previously stable population whose size is now decreasing because they are showing evidence of poor adjustment (e.g., because of genetic defects , acquired metabolic or physiologic disturbances) could not easily be diagnosed as diseased. Many "successful" populations have probably gone through such phases, but developments during them could not have been explained by means of the idea of disease if the condition about deviations posited earlier had been required. In other words, one would be forced to say that the minority of the population did not have the disease which proved lethal to the majority, a claim which thoroughly discredits the condition of deviation from group norms which seemed needed to articulate and...