The medical model
The biopsychosocial model of illness was born in 1977, with a reasonably well-documented gestation. Its growth and development are easily tracked, showing changes and improvements, and anyone can quickly discover the model. In contrast, the medical model, better termed the biomedical model, has been gestating and growing since about 1500, when the Scientific Revolution started. It is not associated with any progenitor and has no definitive text. Indeed, the meaning is uncertain – is a medical model focused on doctors (physicians), or is it focused on disease? I have often referred to the medical model when writing about rehabilitation and emphasised the superiority of the holistic biopsychosocial model. There is no protagonist for the medical model, so I want to discuss its evolution, great success, and decline to a position where it may be causing more harm than good. The medical model will remain relevant in research and disease management but should no longer be the basis for holistic health and social care services. The new Integrated Care Boards in the UK, which combine health and social services, should switch to the biopsychosocial model. The main topics discussed in this post are shown below.
Table of Contents
Introduction
Theories alter the world. A theory is “a supposition or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained”. [Oxford English Dictionary; OED] They enable us to understand and explain observations and, crucially, to predict the effect of changing something. Models are one manifestation of a theory. The model illustrates the idea. A model will make predictions if it can be used mechanically or mathematically.
Many people think developing a theory is a complex, demanding task undertaken by scientists over the years. Few people expect to be forming theories themselves. The opposite is true. One of the brain’s primary functions is to make sense of the stimuli it receives, which involves analysing the data to form a model or explanation (theory).
Every person develops a theory about their body and how it works. This is used to explain new or unusual experiences to decide if they are symptomatic of some bodily dysfunction. These theories are explanatory models of illness. Humankind has speculated on the cause of sickness from the outset. The biomedical model is one of thousands of ideas developed to explain sickness.
Origins of the medical model.
Pre-literate humanity probably attributed sickness to one or more causes centred on gods, other people, nature (the environment), food, or their actions, such as eating or avoiding certain foods. These theories are still common.
Between 5,000 and 10,000 years ago, humans started recording illnesses and their associated symptoms. The study of sickness led to a class of specialists who knew more. The best-known early specialists were from Ancient Greece, though they were not the first. The Romans continued the process of specialisation, gaining expertise in war wounds and surgery.
There was then little progress until the Scientific Revolution. Although there is considerable philosophical debate about the nature and timing of the scientific revolution, David Wootton suggests the process started from about 1500 AD onwards. As the body’s anatomy and function were explored more systematically, a better understanding of sickness mechanisms emerged—professions concerned with diagnosing and treating sickness developed simultaneously. For example, the Royal College of Physicians was founded on September 23rd, 1518, and the Company of Barber-Surgeons was established in 1540; surgeons separated in 1745.
Explanatory theories of disease have existed since humans evolved; a few, such as the four humours, are well-recorded. The scientific revolution stimulated more ideas, which were disproved and replaced. By the nineteenth century, the technology supporting science (microscopes, etc.) had advanced sufficiently to identify specific changes or causes for disease, leading to a more secure medical model. Nevertheless, the social and environmental factors associated with disease were also recognised early on. The investigations into cholera by John Snow in 1854 are a well-known example, as is the work by Florence Nightingale.
The success of science during the nineteenth century in elucidating the nature of sickness, identifying specific diseases and causes, and effective treatments in the twentieth century led to the widespread acceptance of a scientific, reductionist, disease-centred explanatory model of illness. The striking increase in specific, often dramatically successful treatments (e.g. for leukaemia and renal failure) between 1950 and 2000 reinforced the model.
Thus, by 2000, a model of illness focused on disease and treatment had developed over the preceding 500 years and had succeeded in advancing healthcare significantly. Unsurprisingly, it was accepted as the model of illness.
Medical model – a terminological confusion.
Many published articles reject the medical model. Many people conflate using the term medical with the influence of physicians (medical doctors). The content of such papers suggests that the authors are rejecting the involvement of physicians or at least their power.
Georgina Barnes and her colleagues illustrated this in a study of mental health clinicians in the UK NHS. They wrote, “Three core themes were identified: (i) power of a ‘medical model’ and authority of the medic; (ii) responsibility within, and reliance on, a ‘medical model’; and (iii) integrated models of contemporary mental health care. Subthemes arose around organisational culture and low resources affecting the power of a ‘medical model’ and the value of multidisciplinary and person-centred approaches.”
This conflation of disease-based with doctor-driven healthcare arises from the overlap in meaning between medicine as a professional career and medicine as “the science or practice of the diagnosis, treatment, and prevention of disease (in technical use often taken to exclude surgery)”. [OED] This confusion also applies to the confusion between medicine as applying to disease and medicine as referring to physicians rather than surgeons. Most articles fail to identify the focus of concern.
I am not considering any aspects of professional involvement or influence in this discussion. I appreciate that the medical profession (doctors) have more status and power than other healthcare professionals and that not all doctors consider other professionals equal and valued. Discussing culture within healthcare is outside the remit of this post.
To avoid this ambiguity, I will refer to the biomedical model, which is more accurate.
Features of the Biomedical Model
The fundament logic of the biomedical theory is based on two primary axioms:
- All sickness arises from damage to or an abnormality of an organ or structure within the body.
- All changes in the person’s bodily experiences or functioning arise from physical damage or abnormality.
Before further discussion, I will expand on the words used. You can read more about the concepts in another post discussing disease, illness, sickness, and disability.
- Sickness is a socially constructed phenomenon representing a general agreement that the person’s condition allows access to care and support.
- The damage or abnormality is usually abbreviated to a disease; it is the pathology.
- The altered experience or change in function are collectively referred to as symptoms, with the implication that they arise from (and are symptomatic of disease).
- An illness is when the person considers they have a health problem. The healthcare service may not always agree that the person is sick. [One should note that the healthcare service may label someone as unhealthy when they disagree that they are.]
- Diagnosis is the process of identifying the disease causing the symptoms. The word has morphed into standing for the outcome of the process, the disease they have. People refer to someone’s diagnosis, meaning the disease they have.
Axiom A
This is the primary assumption. Every sick person has an underlying disease.
This hypothesis leads to difficulties with any psychological or psychiatric illness. A few psychiatric conditions have associated unequivocal structural neurological abnormalities, but most do not. This can lead to circular arguments such as “I know that depression is a sickness. Therefore, there must be a biological abnormality causing it.” This is extended to the view that “because serotonin uptake inhibitors increase serotonin levels, the pathological abnormality is a low production of serotonin.”
Another significant challenge arises from conditions where people are at the end of a statistically normal spectrum and are thus susceptible to developing some more obvious damage or abnormality. Examples include hypertension, obesity, and alcoholism, which increase the risk of stroke, liver damage, and many other diseases. It is not apparent what the abnormal condition is. For example, when someone says, “Alcoholism is a real disease”, are they suggesting the person would be sick even if no alcohol were available in their community? Are they implying that the person bears no responsibility?
Axiom B
The second hypothesis states that changes in experience or function (symptoms) will only arise due to underlying disease. The result is that anyone whose symptoms cannot be attributed to a disease is not sick.
The theory was well-established before the frequency of symptoms in everyday life had been established. They are ubiquitous. For example, a survey in Denmark recorded that 9/10 people reported at least one symptom in the four weeks preceding the survey date. Many studies report similar findings. Only a minority of experienced symptoms result in seeing a doctor. Even with more severe symptoms, such as shortness of breath or coughing up blood, only 50% saw a doctor.
A third assumption
There is a third unspoken assumption. I have not labelled it an axiom because it is not necessary for the theory but is inextricably linked. The scientific revolution took about a century to gain momentum. In 1641, a French scientist and philosopher, Réne Descartes, introduced the idea that body and mind were separate. This dualist approach has been closely associated with the evolving biomedical theory since. The biomedical theory concerns bodily dysfunction and typically assumes that the mind and all mental health problems exist in some different sphere.
A fourth assumption
A fourth assumption is not axiomatic but is commonly held. When a disease has been identified, all symptoms that that disease might cause are attributed to the disease, and the moderating influence of other variables is discounted.
This pernicious addition does a great disservice to the theory because it overlooks the role of many exacerbating variables, such as anxiety. It also leads, for example, to the pain labelled “failed back surgery”. If, unwisely and against the evidence, someone has an operation for their back pain, they will expect to be entirely free of pain afterwards. They rarely are, not least because the structural abnormalities will rarely significantly contribute to the pain but, more importantly, because other factors such as family and financial stress are still present and are the major causes of the pain.
Quality of the theory.
Theories are valid until disproven, but other factors also indicate quality. The five essential characteristics of a good theory are that it is:
- Testable: making predictions that can be tested; if the forecast is not confirmed, the theory is disconfirmed.
- Coherent, understandable, and logically consistent without contradictions.
- Economical, with fewer variables than other theories covering the same field.
- Broadly applicable, covering almost all instances of the phenomenon, not just in restricted circumstances.
- Explanatory, consistent with all known observations and unexplained or contradictory ones.
I will test the Biomedical Model against these five principles.
It is testable; finding a sickness not due to disease would disprove the theory. There are many examples of conditions accepted as sickness by society that have no associated specific disease, such as functional illness, anxiety and depression, and chronic pain. Thus, the theory is invalid.
The theory is coherent. It is easily understood, and, within its structure, it is logically consistent. It is also economical, probably too frugal, because it does not acknowledge any other variables’ relevant contribution to sickness.
The theory is not broadly applicable. About 20% of all healthcare consultations relate to symptoms that have no underlying disease to account for them, yet the person is often sick for months or years. In the same way, it is not explanatory as there are many unexplained or contradictory observations, such as the persistence of symptoms after the disease has been cured.
It is demonstrably not a good theory. Does that matter? Is there a better theory?
Biomedical theory harms.
A good theory can bring many benefits, but using an invalid theory can lead to harm and loss. For the first 350 years, the biomedical theory undoubtedly led to more benefits than harms as it evolved. However, by the 1950s, its weaknesses were becoming apparent.
In 1977, George Engel published an improved theory of illness, the biopsychosocial model, encompassing and expanding on the biomedical model. He suggested that reliance on the biomedical model led to lower-quality healthcare with a restricted focus. He said, “But nothing will change unless or until those who control resources have the wisdom to venture off the beaten path of exclusive reliance on biomedicine as the only approach to health care.”
In 2004, Peter Halligan and I asked, “Do biomedical models of illness make for good healthcare systems?”. We suggested several problems attributable to using a poor model. In our final sentence, we wrote, “We suggest that the use of our model might improve the delivery of better health more than any other change in healthcare organisation. It is time that the medical models underpinning health delivery were debated openly.”
Nothing much has changed over the last 46 years, and the biomedical model’s exclusive focus on disease still harms patients, wastes resources, and prevents the vital social developments needed. I will give a few examples.
Patient harm.
A mutual belief by doctor and patient that symptoms inevitably and can only arise from disease leads to an increasingly desperate search for the diagnosis, often with increasingly risky or expensive investigations. Disappointment and frustration are the result. The focus on disease diagnosis prevents both parties from considering other, much more likely explanations. This attitude is reinforced by a legal system that punishes a failure to discover some improbable or rare cause when a common psychological or social alternative cause is present.
Additionally, if a structural abnormality is found, such as changes associated with age in the lumbar vertebrae, then treatments aimed at the abnormality will follow. Exacerbating factors like unemployment, financial stress, etc., are ignored, so symptoms remain unchanged. Alternative causes like loneliness and depression are also ignored.
Patients may suffer indirect harm. Society generally devalues sickness not due to disease, and such patients may be stigmatised or ostracised. Some patient support groups reinforce the belief that only a “proper disease” diagnosis for the symptom is acceptable, treating psychologically or socially based sickness as second class or worse.
Second, an excessive focus on searching for “an organic disease” means that evident psychosocial causes of the illness are overlooked or not treated. For example, ignoring treatable depression while investigating headaches or chronic pain prolongs the patient’s unnecessary suffering. The possibility of a specific, treatable pathology does not excuse treating an existing health condition.
Healthcare harm
All healthcare systems are based on the biomedical model of illness. Hospital departments and specialities are primarily centred on organ systems and their diseases; hospital records are structured around biological investigations and bodily systems; and healthcare commissioning is based on disease diagnosis.
One consequence is that crucial information on psychosocial and functional matters is difficult to find or not even recorded. One can quickly discover a person’s haematological parameters when discharged but cannot find if they were walking or talking. The records are not structured to record and identify important personal information quickly.
This extends to and is a consequence of the funding mechanisms centred on disease diagnosis. The weakness of the relationship between disease diagnosis and resources needed for a patient is self-evident. For example, a stroke may leave someone locked-in and dependent or cause only a few days of mild disability with no care needs. The grouping of patients into broad categories encourages gaming, with hospitals selecting patients at the less severe end of a higher-paying group.
Matthew Alcusky and colleagues have demonstrated that methods to account for medical and social complexity are feasible, and using complexity measures such as the INTERMED or OCCAM would help. The Rehabilitation Complexity Score is already available online and is another possible mechanism in rehabilitation.
The failure of healthcare systems to be person-centred is the biomedical model’s most pervasive, pernicious, and invisible consequence. However much an organisation wishes to be person-centred, it cannot succeed when all systems are focused on disease diagnosis. This attitude then affects clinical encounters. Jesus Tiago and colleagues highlighted the crucial requirement for organisations to centre every aspect on the person before genuine person-centred care can occur. I have published a post summarising their paper.
Societal harm
Society makes significant decisions on healthcare. Some of this is through politicians and policymakers, but ultimately, they will reflect the whole population’s wishes and attitudes. Moreover, local culture, not national policymakers, determines how people interact with others with an illness. The model of illness used and understood by everyone has a considerable influence.
For example, it is sad but true that mental health problems are taken much less seriously by the State, many people, and organisations. These attitudes arise from the biomedical model. The model cannot explain such illness; this failure effectively invalidates psychologically based illnesses in the eyes of people who use the biomedical model. The model’s implicit acceptance of mind-body dualism perpetuates this attitude. It also leads to the separation between Mental Health Services and Acute Services, further exacerbating the marginalisation of many illnesses.
The impact is much more comprehensive. The biomedical model ignores the influence of the many factors that adversely impact health, such as the price of alcohol, the high salt, fat, and sugar content of foods, how we legislate about drugs, etc. In every case, the counter-argument is that it is all a personal choice, ignoring the unequivocal evidence that altering social and other factors influences population health. The biomedical model provides a simple, unambiguous solution to complex problems.
Rachelle Buchbinder and colleagues showed the power of social context on health; a public health education programme reduced the relentless increase in back pain. Joel Braslow and Luke Massac discussed how reconceptualising problems affected who became responsible for a “A gravely disabled homeless man with psychiatric illness.”
A better theory exists.
The distressing thing is that a better model has been available for 46 years. The biopsychosocial model of illness may be flawed, but it is much better than the biomedical model. Many, but not all, psychiatrists find the biomedical model inadequate. Brett Deacon has analysed its effects on psychotherapy research, whereas Premal Shah and Deborah Mountain argue there is still a significant role for the biomedical model.
Conclusion.
The Biomedical Theory of illness was a significant advance, facilitating major advances in our understanding of sickness and leading to many effective treatments. However, its success and simplicity led people to forget or overlook illness’s social and psychological aspects. They were known. The biomedical model of illness is no longer a helpful theory and is causing increasing harm. It is not a satisfactory theory. The better biopsychosocial approach incorporates the biomedical theory and, within a fuller context, will continue to support research into biological aspects of illness.
