The biopsychosocial model (abbreviated “ BPS”) is a general model or approach positing that biological, psychological (which entails thoughts, emotions, and behaviors), and social (socio-economical, socio-environmental, and cultural) factors, all play a significant role in human functioning in the context of disease or illness. Indeed, health is best understood in terms of a combination of biological, psychological, and social factors rather than purely in biological terms.  Furthermore, critics of this model have further proposed that spiritual constructs also effect an individuals disease or illness.
This is in contrast to the traditional, reductionist biomedical model of medicine that suggests every disease process can be explained in terms of an underlying deviation from normal function such as a pathogen, genetic or developmental abnormality, or injury.  The concept is used in fields such as medicine, nursing, health psychology and sociology, and particularly in more specialist fields such as psychiatry, health psychology, family therapy, chiropractic, clinical social work, and clinical psychology.
The biopsychosocial paradigm is also a technical term for the popular concept of the “ mind–body connection”, which addresses more philosophical arguments between the biopsychosocial and biomedical models, rather than their empirical exploration and clinical application.  The model was theorized by psychiatrist George L. Engel at the University of Rochester, and putatively discussed in a 1977 article in Science, where he posited “ the need for a new medical model.”
He discusses his model in detail in his paper in the American Journal of Psychiatry [Engel GL The clinical application of the biopsychosocial model, American Journal of Psychiatry 1980; 137: 535-544] where he discusses the fate of a hypothetical patient, a 55 year old Mr Glover who has a second heart attack six months after his first. Engel elegantly indicates that Mr Glover’s personality helps to interpret his chest pain, that he is in some degree of denial and that it is only the intervention of his employer that gives him permission to seek help.
Whereas reductionistically his heart attack can be understood as a clot in a coronary artery, the wider personal perspective helps to understand that different outcomes may be possible depending on how the person responds to his condition. Subsequently Mr Glover in the emergency room develops a cardiac arrest as a result of an incompetent arterial puncture. Once again systems theory can analyse this event in wider terms than just a cardiac arrhythmia. It sees the event as due to inadequate training and supervision of junior staff in an emergency room.
Thus while there may be “ no single definitive, irreducible model has been published,”  Engel’s elegant exposition of his model in this paper gives plenty of scope for this broader understanding of clinical practice. The novelty, acceptance, and prevalence of the biopsychosocial model varies across cultures.  Model description and application in medicine Some thinkers see the biopsychosocial model in terms of causation. On this understanding the biological component of the biopsychosocial model seeks to understand how the cause of the illness stems from the functioning of the individual’s body.
The psychological component of the biopsychosocial model looks for potential psychological causes for a health problem such as lack of self-control, emotional turmoil, and negative thinking. The social part of the biopsychosocial model investigates how different social factors such as socioeconomic status, culture, poverty, technology, and religion can influence health.  However a closer reading of Engel’s seminal paper in the American Journal of Psychiatry (1980) embeds the biopsychosocial model far more closely into patient care.
It is not just about causation but about how any clinical condition (medical, surgical or psychiatric) can either be seen narrowly as just biological or more widely as a condition with psychological and social components, which will impinge on a patient’s understanding of her condition and will affect the clinical course of that condition. Drawing on the systems theory of Weiss and von Bertalanffy, Engel describes the commonsense observation that nature is a “ hierarchically arranged continuum with its more complex, larger units superordinate on the less complex smaller units.”
He represents them schematically either as a vertical stack or as a nest of squares, with the simplest at the centre and the most complex on the outside. He subdivided the vertical stack into two stacks. The first starts with sub-atomic particles and ends with the individual person. The second starts with the person and finishes with the biosphere. The first is an organismic hierarchy, the second a social hierarchy. He then delineates some principles: 1. Each level in the system is relatively autonomous. Thus a cell can be studies just as a cell. 2. Each level depends on the level below.
Thus a cell is composed of nuclei, mitochondria and all sorts of other organelles. 3. Each level is a component of a higher system. Thus cells organise together to become tissues, and organs etc. Thus, “ in the continuity of natural systems every unit is at the very same time both a whole and a part. ” To these principles Engel developed we can add further that higher level properties emerge from lower level systems and cannot be predicted from studying the lower level, We can also add the principle of top-down causation namely that higher levels can influence lower levels.
The biopsychosocial model of health is based in part on social cognitive theory. The biopsychosocial model implies that treatment of disease processes, for example type two diabetes and cancer, requires that the health care team address biological, psychological and social influences upon a patient’s functioning. In a philosophical sense, the biopsychosocial model states that the workings of the body can affect the mind, and the workings of the mind can affect the body.
This means both a direct interaction between mind and body as well as indirect effects through intermediate factors. The biopsychosocial model presumes that it is important to handle the three together as a growing body of empirical literature suggests that patient perceptions of health and threat of disease, as well as barriers in a patient’s social or cultural environment, appear to influence the likelihood that a patient will engage in health-promoting or treatment behaviors, such as medication taking, proper diet or nutrition, and engaging in physical activity.
While operating from a BPS framework requires that more information be gathered during a consultation, a growing trend in US healthcare (and already well-established in Europe such as in the U. K. & Germany) includes the integration of professional services through integrated disciplinary teams, to provide better care and address the patient’s needs at all three levels. 
As seen, for example in integrated primary care clinics, such as used in the U. K. , Germany, U. S. Veteran’s Administration, U. S. military, Kaiser Permanente, integrated teams may comprise physicians, nurses, health psychologists, social workers, and other specialties to address all three aspects of the BPS framework, allowing the physician to focus on predominantly biological mechanisms of the patient’s complaints See also Psychosocial factors can cause a biological effect by predisposing the patient to risk factors. An example is that depression by itself may not cause liver problems, but a depressed person may be more likely to have alcohol problems, and therefore liver damage.
Perhaps it is this increased risk-taking that leads to an increased likelihood of disease. Most diseases in BPS discussion are such behaviourally-moderated illnesses, with known high risk factors, or so-called “ biopsychosocial illnesses/disorders”.  An example of this is type 2 diabetes, which with the growing prevalence of obesity and physical inactivity, is on course to become a worldwide pandemic. For example, approximately 20 million Americans are estimated to have diabetes, with 90% to 95% considered type 2.
It is important to note that the biopsychosocial model does not provide a straightforward, testable model to explain the interactions or causal influences (that is, amount of variance accounted for) by each of the components (biological, psychological, or social). Rather, the model has been a general framework to guide theoretical and empirical exploration, which has amassed a great deal of research since Engel’s 1977 article.
One of the areas that has been greatly influenced is the formulation and testing of social-cognitive models of health behavior over the past 30 years.  While no single model has taken precedence, a large body of empirical literature has identified social-cognitive (the psycho-social aspect of Engel’s model) variables that appear to influence engagement in healthy behaviors and adhere to prescribed medical regimens, such as self-efficacy, in chronic diseases such as type 2 diabetes, cardiovascular disease, etc.
These models include the Health Belief Model, Theory of Reasoned Action and Theory of Planned Behavior, Transtheoretical Model, the Relapse Prevention Model, Gollwitzer’s implementation-intentions, the Precaution–Adoption Model, the Health Action Process Approach, etc. Criticism Some critics point out this question of distinction and a question of determination of the roles of illness and disease runs against the growing concept of the patient–medical tradesperson partnership or patient empowerment, as “ biopsychosocial” becomes one more disingenuous euphemism for psychosomatic illness.
This may be exploited by medical insurance companies or government welfare departments eager to limit or deny access to medical and social care.  Some psychiatrists see the BPS model as flawed, in either formulation or application. Epstein and colleagues describe six conflicting interpretations of what the model might be, and proposes that “… habits of mind may be the missing link between a biopsychosocial intent and clinical reality.”
Psychiatrist Hamid Tavakoli argues that the BPS model should be avoided because it unintentionally promotes an artificial distinction between biology and psychology, and merely causes confusion in psychiatric assessments and training programs, and that ultimately it has not helped the cause of trying to destigmatize mental health.  Sociologist David Pilgrim suggests that a necessary pragmatism and a form of “ mutual tolerance” (Goldie, 1977) has forced a co-existence of perspectives, rather than a genuine “ theoretical integration as a shared BPS orthodoxy.”
Pilgrim goes on to state that despite “ scientific and ethical virtues,” the BPS model “… has not been properly realised. It seems to have been pushed into the shadows by a return to medicine and the re-ascendancy of a biomedical model. “ However, a vocal philosophical critic of the BPS model, psychiatrist Niall McLaren, writes: “ Since the collapse of the 19th century models (psychoanalysis, biologism and behaviourism), psychiatrists have been in search of a model that integrates the psyche and the soma.
So keen has been their search that they embraced the so-called ‘ biopsychosocial model’ without ever bothering to check its details. If, at any time over the last three decades, they had done so, they would have found it had none. This would have forced them into the embarrassing position of having to acknowledge that modern psychiatry is operating in a theoretical vacuum. “