Are Models Irrelevant and Incoherent?

Bolton’s (2014) article provides a wonderful sketch of the problems facing the Biopsychosocial model. His analysis is pithy and provocative. I focus on the conceptual issues he raises, with the aim of soliciting clarifications about his position. I will also argue that his argument has more radical conclusions than he himself spells out.

It is difficult to get a grip on what a model of disease is meant to achieve. It is different from an analytic definition of disease, which presents necessary and sufficient conditions for what conditions count as disease. It is also different from giving a paradigm case of disease with the aim of explaining the meaning of a disease without providing necessary and sufficient conditions. Similarly, it is different from explaining disease as a cluster of concepts that are connected by family resemblance. But if it is not about definition, then what does a model aim to achieve?

The debate between those who advocate a biomedical model and those who support a Biopsychosocial model of disease seems to be more about how to understand disease in general, or how to understand the diseases of particular people. But still this is very vague. The contested issue seems to be about what is the most fundamental level of description of a disease: a biomedical approach says it is a biological description, while a Biopsychosocial approach denies that one level is fundamental, and insists on a pluralist approach, combining biological, psychological, social, and whatever other levels may exist. The difference looks like one of ontology.

But still, the notion of fundamental is here far from transparent. There is much shared ground between the two approaches. They both agree that there are different levels of description and theorization of disease, which Engel (1980) refers to as the “systems hierarchy.” They both agree that there may be psychological and social factors that impinge on what happens at the biological level, and that biological events have psychological and social effects. No defender of a biomedical model has claimed seriously that all psychological and social events can, either now or in some distant future, be described in biological, chemical, and physical terms, and of course it is essential to the Biopsychosocial model that the different levels of description are not translatable. Yet at the same time, there is broad agreement on both sides that the psychological levels of description must in some ways supervene on the lower levels, and similarly for the sociological levels, in the sense that the higher levels in some way depend on the lower levels.

If it turns out that the differences between the Biomedical and the Biopsychosocial approaches are not ontological or metaphysical, it comes to seem that the real difference is one of emphasis on what is useful when a doctor is trying to understand what is wrong with a patient. A biomedical approach urges putting the biology of the patient front and center, and paying only secondary attention to psychological and social issues, whereas a Biopsychosocial approach says that a doctor should be sensitive to all levels understanding a person’s medical problems, and always looking for possible connections between them. If this is the difference, then it should be verifiable experimentally, which approaches work with different kinds of medical problem. Then the dispute is really an empirical one, even if the empirical hypothesis being tested remains rather elusive.

Bolton highlights Engel’s analysis of the biomedical approach that if a problem is not reducible to biological problems, then it is not a medical problem. This is a definitional move: it says that diseases need to be understandable in terms of biochemical or physical problems. It is then a claim about the domain of the medical. Bolton explains Engel’s criticism as rejecting this definition of disease. This is not just a semantic issue, but also a question of professional domains: physicians will only treat diseases, and other professionals (psychologists and social workers) will treat other kinds of problem. Engel’s insight was that a separation of domains was not only artificial but also bad for patients...