A Systems Theory Approach to an Expanded Medical Model:A Change for Biomedicine

Introduction

As practitioners, we approach our patients and their problems within the framework of a conceptual model that organizes and defines the questions we ask, the information we seek, the diagnostic and therapeutic options, and ultimately the outcome of our interventions. Because we are so accustomed and conditioned to think and act within a specific framework, we rarely if ever consider the fundamental conceptual principles underlying our practice even though these principles can assume a powerful, although often unseen, authority over our professional lives.


The dominant medical model of Western culture, the biomedical model, is based on three underlying, yet untested, assumptions and principles: (1) objectivism, the idea that accurate knowledge can be exclusively achieved through an impersonal assessment of sensory based information; (2) determinism, the idea that causation is exclusively characterized by an upward and linear mechanistic linkage; and (3) positivism, the idea that knowledge exclusively accumulates through the accretion of data from the positive results of sensory based experimentation. This model has served us well, but with the progressive urbanization of life accompanied by the industrial and technologic revolutions humankind has seen the development of new and very different adversities, which have resulted in the emergence of a uniquely new category of modern day ailments, particularly stress related diseases, acute and chronic that are directly linked to personal attitudes and lifestyle. As a result, the limitations of a medical model that cannot effectively incorporate psychological, psychosocial, or spiritual factors-factors that are at the source of these ailments-has become increasingly evident.


The emerging public interest in health promotion, self-care, alternative healing practices, and mind/body medicine is a response to the limitations of the biomedical model and challenges future health practitioners to develop a more comprehensive understanding and approach to the care of individuals (Eisenberg et al., 1993). Ideally, such an approach would maintain the scientific rigor and discipline that has so successfully served the biomedical model while at the same time expand the vision and reach of modern medicine. New approaches to clinical care must be developed in a manner that can be easily integrated into clinical training and effectively assist the future practitioner in meaningfully expanding his or her capacity to respond to the changing needs and demands of a diverse population of clients.


The comprehensive model proposed here incorporates and integrates the principles and practices of the biomedical model with the new and emerging initiatives noted above. It does so by presupposing that there are multiple maps and explanatory models for perceived reality. Each map is considered valid in itself, yet when considered together they provide a closer approximation to reality than is possible when each is taken alone. As complex beings living in a complex ecology, we can appropriately and simultaneously be considered as instinctual beings whose systems are amenable to repair, interactive units whose major component systems are the mind and body, and spiritual beings who emerge from and ultimately rejoin the timeless flow of nature. The model I am proposing will consider each of these aspects of our being-instinctual, mind/ body, and spiritual-their relationship to each other, and the manner in which each can be integrated into a comprehensive approach to health.


This approach will be based on new set of assumptions and principles which incorporate, yet expand upon, those of the biomedical model. The first principle, dynamism, reflects the view that the human experience is at all times in an active and vital relationship with its environment, continuously exchanging nutrients and information and adapting to new and different circumstances. Unlike a machine that cannot change itself once it is set in motion, humans can repair their own tissues, regenerate new tissue, and through will adapt to varying external conditions by altering their actions. The second principle, holism, is the term that we use to designate the viewpoint that human life is a natural, self-organized, unfolding process that consists of constituent elements bound together from the very beginning as a unitary interactive whole. If an embryo is homogenized into a soup that contains all of its initial ingredients (DNA, RNA, and so forth) it is not possible to reconstitute a living embryo from these isolated parts. The memory and pattern of the whole precedes the development of the parts and is disrupted when the intact living process is altered. The final principle, purposefulness, intentionality and goal directed activity, can be found at every level of the human experience: The automatic mechanisms of homeostasis are directed towards maintaining a precise physiologic balance; the in-born psychic instincts, the Jungian archetypes, outline the patterns, intentions, and directions of psychologic development which sustain a continuity and stability of the human experience; and consciousness appears to follow the universal quest to expand itself sufficiently to understand and re-unite with the ground of its being. Together, these three principles extend our understanding of the human condition and recognize the full range of healing capacities built into the human mind and body.


Systems Theory


Based on these new assumptions and principles, the model I am proposing draws upon the knowledge of systems theory that first developed as a modern response to the accumulation of expanding volumes of information and data and an increasing emphasis on microspecialization. Systems, or organizational theory, is an attempt to integrate, to create wholes out of parts. It is in essence a science of wholeness. Its concepts and principles are based on the observation that nature is organized in patterns of increasing complexity and comprehensiveness, and that these larger wholes, or units, have characteristics and qualities unique to the whole and cannot be identified or accessed through an analysis of their component parts (Weiss 1977; van Bertalanffy 1968). For example, the human organism, composed of cells, tissues, and organ systems, contains qualities and characteristics that cannot be exclusively accounted for through the linear summation of its parts. These include the capacity for self-organization, integrated action and adaptability, will, intention, and creativity.


In the 1970s George Engel, using the principles of systems theory, developed the biopsychosocial model, an expanded model of healing (Engel 1980, 1982). His intent was to extend the biomedical model to include the psychologic and psychosocial factors that are largely excluded from it. The model I am proposing similarly draws upon systems theory, but unlike Engel’s biopsychosocial model, which is based on the biosocial hierarchy of nature, the health continuum is based on a hierarchy of healing systems, which are seen as the essential linkage between cellular physiology and social adaptability. The model is composed of four healing systems: homeostasis, treatment, mind/body, and spiritual. Figure 1 illustrates the relationship of the component parts to the whole.




Fig. 1. The health continuum.



Each of the subsystems of this model is a complete and distinct whole in itself, yet at the same time it is part of a more comprehensive healing system. As an intact system, each of these component systems has its own frame of reference, operating principles, internal stability, characteristics, and research methodology. As we ascend the hierarchy of healing systems we expand our conceptualization of healing, adding both complexity and comprehensiveness at each new level. Each component of the systems can be studied separately, and the entire system can be studied both in terms of its system wide characteristics and the interrelationships of its component parts. For the scientific researcher, it is appropriate to selectively study a particular system applying the research methodology appropriate to the system under study. The practitioner, however, whose focus is always the whole person, must have the dual concern of attending to the individual components of the healing system while simultaneously considering these components within the context of a more inclusive and comprehensive multisystem approach to healing.


System 1: The homeostatic healing system

Walter Cannon described the most primary and basic healing system available to the human organism, the homeostatic system (Fig. 2). This built-in instinctual system of internal physiologic checks and balances evolved over the millennia of human development, providing the human organism with the potential to automatically respond to internal states of disequilibrium with immediate, reflex like physiologic corrections. This system assures the maintenance of a steady physiologic state, which in turn ensures survival.


However, our homeostatic system is far more suited to the life of primitive humans than it is to the more recent and dramatic changes in lifestyle and environment that characterize and accompany “civilized” urban life (Williams and Neese 1991). As a consequence, the homeostatic system is often maladapted to the changing lifestyles, practices, and environments of modern humans: our nutritional choices, exercise patterns, physical environments, and above all our stress levels. This mismatch of primitive adaptive mechanisms and the realities of modern life have resulted in significant limitations and deficiencies in the natural protective mechanisms designed into this system. For example, the maintenance of normal glucose levels and the integrity of our vasculature is undermined by our modern day diet and sedentary lifestyle, and the on and off mechanism of the stress response and the maintenance of normal levels of blood pressure are distorted by the presence of unrelenting mental stress. To remedy the results of the mismatch between the built-in mechanisms of the homeostatic healing system and the realities of urban life civilized man has developed “treatment” models whose purpose is to step-in where homeostasis has failed and to restore normal function.





Homeostasis
Treatment
Mind/Body
Spiritual








Consciousness
Mechanism
Process
Focus
Resources
Health













Instinctual
Reactive
Intentional
Intuitive
Autoregulation
Repair
Self-Regulation/
Self-Exploration
Integration
Checks and Balances
Reductive
Developmental
Unifying
Disequalibrium
Disease
Person-Centered
Myth/Symbol
Feedback Loops
Drugs/Surgery
Alternative Therapies
Mind/Body
Consciousness
Steady State
Restore Funtion
Autonomy
Wholeness



Fig. 2. The Health Continuum.



System 2: The treatment heating system

The treatment system is activated when the patient seeks assistance from a health-care
practitioner as a reaction to the appearance of a symptom or the presence of overt disease, an indication of the breakdown of the natural homeostatic system. This is routinely followed by the requisite testing, establishment of a diagnosis, and the prescription of therapy, usually, in the biomedical treatment system, in the form of external agents such as drugs, surgery, or physical therapy (Fig. 2). Biomedicine, the dominant form of treatment in western society, seeks to establish and explain causation by reducing the field of study to a single body system and its associated biochemistry. Its aim is to repair the biophysiologic abnormality and re-establish health, which in the biomedical system is defined as the restoration of normal function.


The success of biomedicine has resulted in a shift in the burden of illness from acute infectious disease to chronic, often stress related, degenerative disease, the causes of which are largely a result of personal attitudes and lifestyles. Although biomedicine is well equipped to diagnose and treat these diseases, which are currently the major source of premature death and morbidity, its therapies rarely result in cure. The characteristics that have been responsible for biomedicine’s many accomplishments by necessity also define its limits. A reductive system, by its very definition, is incapable of meaningfully including psychologic and psychosocial factors, which cannot be exclusively reduced to the level of biochemistry without losing their complex and interactive meaning and significance to the human experience. For this, we must extend our vision of healing to consider the mind/body healing system, which both incorporates the homeostatic and biomedical systems while extending them to include factors that were previously excluded.


System 3: The mindbody healing system

The mind/body healing system relies on the assumption of personal responsibility and the self-motivated effort to develop and use the personal skills and capacities-psychological, psychosocial, and physical-that are available to assist in the process of self-regulation and healing (Fig. 2). Mind/body healing is intentional and preferably proactive. Its focus is on personal attitudes and lifestyle, the central factors in the development of stress related degenerative disorders. The concern here is with psychological development, individuation, personal transformation, and mastery, to the extent possible, over the activities of the mind and body.


This aspect of healing finds its scientific legitimacy in the emerging research in the field of psychoneuroimmunology (Ader et al., 1991). The discovery of the interconnectedness of psychic and physiologic functions mediated by the mobile neuropeptide messenger system has assisted in establishing the biochemical pathways that account for the long accepted relationship between mind and body. Further, we are now able to demonstrate the specific psychological qualities and psychosocial influences that appear to provide enhanced resistance to the detrimental effects of physiologic stress (Antonovsky 1988, 1991; Kobassa 1979).


The shift in focus from diagnostic categories to issues of personal attitudes, lifestyle, and psychological development alters the relationship of the health practitioner to the patient, perhaps better referred to here as the client. The relationship is more of a partnership than the hierarchical relationship that characterizes biomedical healing. The focus is long term and the treatment modalities, which can more accurately be termed health promotion practices, are more internal than external. Examples include meditation, exercise, nutritional practices, psychosocial education, biofeedback, and yoga. The intent is more educational than therapeutic and the health practitioner serves more as an educator and coach.


As with each of the preceding systems, the defining focus of the mind/body healing system-psychological development and individuation-also accounts for its deficiencies and defines its limits. This system fails to consider the spiritual aspects of the human experience, which transcend and extend the boundaries of personal development, conveying to the individual a more comprehensive and sustaining understanding of the living experience.


System 4: The spiritual healing system

There are many definitions of spirituality, but for the purposes of this model I have chosen to define spirituality as an individual’s capacity to view the living experience in the context of an organized and unifying perspective that transcends day-to-day experience and provides meaning and purpose to the essential human concerns about life and death. A spiritual perspective can have a profound effect on personal attitudes, values, and behaviors, and consequently on biochemistry and physiology. These effects on the mind and the body are termed spiritual healing.


Of the healing systems discussed in this paper, the spiritual healing system is the most difficult to define and presents the most significant challenge to our current research methodologies. Yet it conveys an essential completeness and wholeness to this comprehensive healing model by encouraging an existential exploration of the primal human issues of pain and suffering, disease, aging, and death, their meaning and purpose.


The Health Continuum


When these four healing systems are considered as an integrated comprehensive system
certain characteristics appear that are not evident when each is taken separately. We are able to see the evolving characteristics of healing as we approach Figure 2 in a horizontal direction. For example, the expansion of consciousness from instinctual to reactive, intentional, and intuitive; the shift in resources from built-in automatic feedback loops to drugs and surgery, mind and body, and finally to an expanded consciousness. Similarly we can see an increasingly inclusive and comprehensive vision of health as we shift from the goal of maintaining a physiologic steady state to restoring function, to individuation, and finally to the attainment of wholeness. Taken as a whole, the movement through each healing system reflects the natural developmental sequence of a human life. We discover that much like this model, we are both parts and wholes; mechanical, interactive, and integrated all at the same time.


The adversarial distinction between conventional and holistic/alternative therapies disappears as we consider the intent, usefulness, and mechanism involved in each form of therapy and properly assign it to one of the four healing systems: homeostasis, treatment, mind/body, and spiritual. This is a more functional way to categorize a therapeutic practice than the current arbitrary and capricious view of its status as “conventional” or “holistic/ alternative.” To the extent that a practice, conventional or holistic/alternative, fits within a specific system, it then, by necessity, must attain its legitimacy and credibility through the disciplined exploration of its efficacy by means of the research methodology appropriate to that specific system.


This model is inclusive rather than exclusive, honoring and respecting the contributions, independence, and interdependence of each of these healing systems and the integrity and professionalism of the many and varied practitioners whose practices, when proved efficacious through a rigorous system based research methodology, serve as accepted and valuable resources for one or more of the healing systems. Reductionistic and holistic thinking, and conventional and alternative practices are each seen as essential components of a comprehensive intellectual process and a unified approach to health and healing.


Clinical Decision Making


It is in the context of this model that we can now explore how practitioners-in-training and the active clinician can incorporate these perspectives into the daily practice of healing. In the biomedical system we are accustomed to using a symptom as the “ticket of admission” to the clinical setting and as the basis for the ensuing interview, which begins with a general review of the body systems and progresses, in a reductionistic manner, toward a subsequent focus on the particular single system most directly related to the presenting symptom. This process can be directly applied to the expanded approach proposed here by adding an initial level of triage, which precedes the more detailed interview process. This initial triage decision determines which one or more of the healing systems-homeostatic, treatment, mind/body, or spiritual-is to be applied to the presenting problem. This decision is based on three critical factors: intensity and severity of the illness, age, and mindstyle of the patient (Fig. 3).


For example, a minor acute illness is not the basis for a multisystem interview. In contrast, a myocardial infarction requires full attention to the homeostatic, treatment, mind/body, and spiritual healing systems. An individual’s age further assists in determining the applicability and usefulness of the mind/body and spiritual healing systems. Mind/body healing cannot be introduced until the attainment of a certain level of maturity, and similarly, a spiritual approach is generally inappropriate for the adolescent or young adult. Mindstyle is the final indication of which direction to proceed. The latter two healing systems require a certain openness, interest, and intellect as they call upon the direct and enthusiastic participation of the client.




Fig. 3. Multidimensional Healing: The Clinical Process.



Once made, this triage decision defines the next level of inquiry, which consists of an interview related to the particular healing system(s) that have been selected. If the problem seems most appropriately resolved through the biomedical approach the traditional review of systems ensues. If an alternative approach is selected, the specific approach-based interview is conducted. If the problem calls for the mind/body or spiritual systems, the inquiry appropriate to these systems is inserted. Briefly, the homeostatic system is concerned with the circumstances environmental, dietary, and physical-that support the normal auto-regulatory functions of the mind and body; the treatment system focuses on the traditional issues of diagnosis and therapy, the mind/body system is concerned with personal attitudes and lifestyle, and the spiritual system considers issues of meaning and purpose. As with the traditional review of systems, an inquiry into each of these aspects of healing proceeds with a series of questions and responses between practitioner and client.


With the above considerations and the appropriate inquiry into the nature of the presenting problem, a comprehensive plan can be agreed upon in partnership with the client. This plan will apply the appropriate range of resources from each of the selected healing systems. In its most complete form such a plan would aim to support the normal operations of the homeostatic system, restore function where dysfunction has developed (the treatment system), expand personal resources and capacities (the mind/body healing system), and assist the individual in the attainment of a more whole and balanced life (the spiritual healing system). As with any plan, there is a continuing reiterative process that occurs throughout the life cycle.


To better illustrate this process let us consider the case of an individual who presents for the first time with the symptoms of atherosclerotic heart disease. The initial triage would suggest that the age at which this disease presents itself and the intensity and severity of this particular illness indicates the need to consider, at a minimum, the treatment and mind/body healing systems. Further inquiry, which may continue over weeks, will clarify whether this specific individual is amenable to viewing the implications of his or her disease within the framework of a spiritual perspective. Initially the appropriate steps related to treatment, diagnosis, and therapy are pursued. Concurrently, an inquiry into personal attitudes and lifestyle are initiated. Finally, if appropriate, a dialogue can be initiated, which is directed toward seeking an understanding of
the meaning, purpose, significance, and implications of this disease for the individual’s life.


In this case the development of a comprehensive plan would include a mixture of approaches: the use of appropriate diagnostic and therapeutic interventions (the treatment system), the introduction of attitudinal and lifestyle changes in the areas of stress management, nutrition, exercise, and insight based psychological counseling (the mind/body system), and an ongoing consideration of the impact of this illness on previously held values, beliefs, and priorities (the spiritual system). The goal for the practitioner is to begin to perceive disease and the individual in a larger context. For the individual, the goal is to use disease as a doorway into a more considered and expanded life-one that both serves to remedy the problem at hand, reverse the personal factors that have contributed to the development of the illness, and enhance the overall quality of life.


The Clinical Setting

At this juncture it is reasonable to ask “How can such a model be integrated into the contemporary health care setting, and more specifically, the biomedical model?” As a consequence of the introduction and expansion of managed care delivery systems, individuals have increasingly lost their capacity to directly access specialty care practitioners. As a result, the primary care practitioner has become the door of entry into the medical care system. Therefore, it is the primary care practitioner who will become the critical triage officer. This most important and highly trained individual must have the capacity and skill to triage problems according to the levels of care required and to train and supervise others to do the same. Although the primary care practitioner should coordinate and overview the various aspects of care, the individual components of the health care plan can be implemented by a variety of individuals trained in each of the specific healing modalities. This would require a reorientation of the clinical setting to allow for a variety of intervention formats in contrast to the exclusively biomedical approaches of our current system.


It is important to recognize that mind/body and spiritual healing approaches are largely educational in contrast to therapeutic. It is therefore preferable that practitioners can easily access educational programs, off-site or on-site, which provide these services in group formats. To a considerable degree the resources of mind/body and spiritual healing, which are not currently considered in clinical settings, are best provided for in educational, nonclinical environments, and the distinction between medical therapeutics and person-centered education slowly disappear as we shift toward the latter levels of healing.


Practitioners and Clients: Partners in a New Perspective


This proposed model has very definite implications for practitioners and their clients. If primary care practitioners are to perform the role of triage officers as proposed here, they must be provided with an integrated systems based education. Such a physician must be knowledgeable in the dynamics of each of the four healing systems, but the distinctive aspect of his or her education will be an understanding of the principles, concepts, and structural issues that underlie a comprehensive approach to healing. We are not seeking experts in specific domains. The level of data and information available makes that task impossible. Rather, we are seeking practitioners, conventional and “alternative,” whose training is expanded to include an understanding of each of the essential aspects of healing complemented by a strong emphasis on integrative studies. The latter is not merely an emphasis on structure and organization, but contains a value system that emphasizes synthesis and wholeness, a perspective that is largely absent from current educational programs.


Similarly, our clients must also review their monotheistic and fragmented approach to health care. It will be increasingly necessary to view health as an artistic creative act, one that is engaged for the duration of the life cycle. The expansion of consciousness, self-knowledge, capacities, resources, and skills is the very process of health itself. In these terms health
becomes more a verb than a noun, an intentional and proactive orientation to life that values personal growth and development. Health is then viewed as a lifetime journey rather than as a response to illness. In this context, a consciously lived life cycle will engage an individual in exploring each of the healing systems and in this manner maximize their contributions toward enhancing the quality and duration of life while simultaneously compressing morbidity into the final years of life.


Shifting Paradigms

Thomas S. Kuhn, in his seminal work The Structure of Scientific Revolutions (Kuhn 1970), suggests that scientific paradigms that serve to tightly organize and structure the development of a particular field of study will in time progressively fail to account for anomalous findings. The tenaciousness of an entrenched paradigm will, through denial, discounting, or other attempts to sustain itself, invariably delay the crisis that will inevitably confront an increasingly inadequate model. Eventually, more comprehensive models will develop, and a competitive battle will ensue between old and new.


This is our current circumstance. The biomedical treatment model, as a direct result of its very successful reductive approach, cannot adequately incorporate the significance of psychological, psychosocial, and spiritual factors of health. It cannot make sense of and respond to the extensive literature that documents the effect of social support and socioeconomic influences on morbidity and mortality (Adler et al., 1993; Berkman and Syme 1979; House et al., 1982; Williams et al., 1992). It cannot easily acknowledge and integrate an exceedingly well documented lifestyle and psychosocial based program for the nonpharmacologic reversal of coronary atherosclerosis (Ornish 1990). There is no accommodation for the increasing research in the field of psychoneuroimmunology, which is demonstrating the relationship between mental attitudes and physiologic change, and no explanation for the well documented reversals of what are considered terminal diseases (O’Regan and Hirshberg, 1993). Finally, there is no consideration of the potential efficacy of “nonconventional” therapies or the emerging and growing public interest in health promotion.


Beyond these issues are the social and cultural consequences of the biomedical treatment model, which have become progressively detrimental to the human experience. The social roles assumed by practitioner and client, roles that are a direct consequence of the professionalism and authoritarianism of modern medical practices, and the “medicalization” of many aspects of human life (e.g., socially deviant behavior) have undermined the development of personal autonomy and responsibility, the very qualities that are essential for both human development and for access to the extended aspects of healing. Further, the cultural view of essential human concerns such as disease, health, pain, suffering, and death, are increasingly defined in medical and pathologic terms. For example, pain and suffering, which can be viewed as an existential issue to be lived through and grown from, have now become something adverse to fix and remove. They have shifted from personal concerns to technologic medical problems, from a source of knowledge and wisdom to an unwanted disruption in life.


In response to these concerns we have seen the development of various new models and approaches: the wellness model, the biopsychosocial model, and mind/body, holistic, and alternative practices. Each of these initiatives is a response to our current dilemma: the inability of the biomedical treatment model to fully respond to the needs of our time. The model I am proposing incorporates these ideas into a singular expanded vision of the future, one that is inclusive, comprehensive, accessible, and functional. This model can serve to responsibly integrate conventional practices with the emerging interest in mind/body and spiritual healing, alternative therapies, and health promotion initiatives, provide a theoretical basis for new system based research methodologies, assist with the development of an expanded curriculum for practitioners, and serve as the template for an innovative and flexible approach to healing that responds to
both individual and social needs as they have emerged in our time.




References


Ader R. Felten DL, Cohen N. Psychoneuroimmunology. 2nd ed. New York, NY: Academic Press, 1991.


Adler NE, Boyce WT, et al. Socioeconomic inequalities in health. JAMA 1993;269:3140-3145.
Antonovsky A. Unraveling the mystery of health. San Francisco: Jossey-Bass, 1988.


Antonovsky A. Health, stress, and coping. San Francisco: Jossey-Bass, 1991.
Berkman LF, Syme SL. Social networks, host resistance, and mortality: A nine-year follow-up study of Alameda county residents. Am J Epidemiol 1979;109:186-204.


Eisenberg D, Kessler R. Foster C, Norlock F. Calkins D, Delbanco T. Unconventional medicine in the United States: Prevalence, costs, and patterns of use. N Engl J Med 1993;328:246-252.


Engel G. The biopsychosocial model and medical education. N Engl J Med 1982;306:802-805.


Engel G. The clinical application of the biopsychosocial model. Am J Psych 1980;137:535-544.


House JS, Robbins C, Metzner HL. The association of social relationships with mortality: Prospective evidence from the Tecumseh community health study. Am J Epidemiol 1982;116:123-140.


Kobassa SC. Stressful life events, personality, and health: an inquiry into hardiness. J Personality and Social Psychology 1979;37:1-11.
Kuhn TS. The structure of scientific revolutions. Chicago: University of Chicago Press, 1970.


O’Regan B. Hirshberg C. Spontaneous remission: An annotated bibliography. Sausalito, CA: Institute of Noetic Sciences, 1993.
Ornish D. Dr. Dean Ornish’s program for reversing heart disease. New York: Random House, 1990.


Von Bertalanffy L. General systems theory. New York: Braziller, 1968.
Weiss P. The system of nature and the nature of systems: Empirical holism and practical reductionism harmonized. In Schaeffer KE, Hensel H. Brody R. eds. Toward a man-centered medical science. Mount Kisco, NY: Futura Publishing Company, 1977.


Williams GC, Neese RM. The dawn of Darwinian medicine. Qu Rev Biol 1991;66:1-22.


Williams RB, Barefoot JC, et al. Prognostic importance of social and economic resources among medically treated patients with angiographically documented coronary artery disease. JAMA 1992;520-524.


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