This book is about the most general model in medicine and health care: the much-celebrated biopsychosocial model, first introduced by George Engel in the 1970s (Engel , ). Although the model is taught in practically all medical schools, it is plagued by a number of fundamental problems. Critics have deemed the model vague, short of empirical validity, clinically useless, and metaphysically obscure—if not incoherent (for example, Ghaemi ). Bolton and Gillett take on the task of addressing all these concerns in this book, aiming for a philosophically defensible and scientifically updated version of the model. Considering the continued dominance of biomedical thinking in health care, evidenced by the rise of biology-based psychiatry, this book is both important and timely.
Bolton and Gillett argue in the opening chapter, with clarity and force, that the biopsychosocial model is best taken as a general model. Its value isn’t found in any predictive or explanatory power as some critics have supposed; by itself, the model explains and predicts very little. Instead, Bolton and Gillett argue that the biopsychosocial model offers a framework to understand the aetiology of specific health conditions. For many health conditions, it is now evident that biological, psychological, and sociological factors are all part of the causal nexus. Myocardial infarctions, for instance, have been associated with a large range of causally relevant factors—some biological, others clearly sociological (for example, social determinants of health like economic class, access to health care, dietary habits) and psychological (attitudes, values, capacity for behavioural change, willingness to accept therapy, and so on). As Bolton and Gillett demonstrate with a score of examples and empirical support, the complex causal nexus of specific health conditions makes up the scientific content of the biopsychosocial model. The model is a framework to understand these complex aetiologies.
Nevertheless, the framework raises many philosophical questions: How do these different factors interact? Is one level of explanation more fundamental than others? How can one health condition permit of so many causal explanations? Bolton and Gillett spend most of the book addressing these deeper philosophical questions. They do so, initially, by fending off two philosophical enemies: reductionism and physicalism. According to reductionism, complex phenomena can be brought back to one kind of cause or one level of explanation—be it biological, psychological, or sociological (p. 26). Physicalism is the view that everything that exists is physical, so that the only real causes are physical causes (p. 26)—meaning we can discard psychosocial causes of health conditions. As Engel already made clear, physicalism and reductionism are crucial to the biomedical model: it privileges biochemical explanation as the only real explanation of health conditions. Undermining physicalism and reductionism, however, is an enormous task. Despite the wealth of philosophical resources from which the authors draw, it should come as no surprise that the book doesn’t quite succeed in escaping the grip of physicalism and reductionism. I will point out a few limitations before taking a step back to reflect more generally on their view of the biopsychosocial model.
Bolton and Gillett seek to undermine reductive physicalism by focusing on the irreducibility of biology to chemistry and physics. The way biological explanation cannot be reduced to physical explanation, then, is supposed to serve as blueprint for genuine psychosocial explanation. The argument runs as follows: Biological organisms are characterized by their ability to resist entropy, developing and maintaining their form, and reproducing before succumbing to entropic forces and turning back into dust (p. 47). The key to understanding how biological organisms do so is the notion of information-based regulatory control mechanisms (p. 47). Genes provide the information to encode for RNAs that build proteins, regulating the organism in its environment so that it maintains its form and function (pp. 46–50). Concepts like ‘information’, ‘encoding’, ‘regulating’, ‘form’, and ‘function’ have no place in the purely physical explanations of physics. Biology requires a different form of explanation, invoking normative differentiations like error and success, function and dysfunction. Hence, biological processes cannot be explained purely at the level of physics. Regulatory control mechanisms in biology are a type of causation, so must be permitted as equally real and explanatory as physics. They continue with a similar account of psychosocial explanation, equally portrayed as irreducible to biological and physical explanation.
Now, there are two immediate and relatively familiar problems with this sort of approach. The first becomes apparent when we ask what ‘information’ and ‘coding for’ really mean. This is Bolton and Gillett’s definition of ‘coding’: ‘in normal circumstances, in the normal cellular environment, in a complex series of interlocking steps, such-and-such DNA sequence produces such-and-such protein’ (p. 55). We find a similar sort of physical detailing of agency, defined in terms of the working of the central nervous systems (p. 82). What are these, we should wonder, other than physical, reductionist definitions? The language of biology may be teleological and goal-oriented, but if on closer inspection the terms refer to processes that can be entirely described in physical (or dispositional) terms, we still end up with what very much looks like a reductive and physicalist position. The reference to systems theory does little to counteract this worry, in my view.
Second, arguments like the one offered by Bolton and Gillett are vulnerable to the problem of causal overdetermination, first discussed in the philosophy of mind (Kim , ). Biological regulatory control mechanisms may be a genuine form of causation. But those mechanisms are themselves composed of causal processes at a physical level. If so, one phenomenon or event appears multiply determined and explained, which most view as metaphysically incoherent. Bolton and Gillett briefly mention this concern (p. 63), but brush it aside as not applying to their view. Although the book does not shy away from serious metaphysical questions and theories—which is admirable for a book in the philosophy of medicine—these issues aren’t worked out further. Instead, the book gets slightly distracted with less relevant issues, like causation by non-occurring events (p. 66). This is a shame, as theoretical clarity on the irreducibility of biological and psychosocial causes would certainly help lift the biopsychosocial model out of philosophical obscurity.
Besides these metaphysical worries, there is a more general concern I would like to raise. Bolton and Gillett’s central claim is that a biopsychosocial model is required because factors of all three kinds are causally involved in bringing about, maintaining, and determining the course of health conditions. This causal approach departs, to a significant degree, from Engel’s original intentions. Engel wasn’t so much interested in causes of health conditions; his idea was that health conditions themselves have important psychosocial dimensions. Next to biomedical aspects, Engel pointed out that the human experience of illness is important, as this determines whether or not someone is ill in the first place. Psychological and behavioural expression of illnesses are also significant, meaning that physicians must be able to understand the socially and culturally shaped ways in which patients communicate symptoms. Psychosocial factors further determine when someone accepts the sick role in a given society. And, finally, the physician–patient relationship also affects the way illnesses are experienced and expressed (Engel , pp. 131–2). Engel’s aim with the biopsychosocial model, then, was to widen the understanding of the health condition itself, not their proximal and distal causes. In Engel’s (, p. 132) words:
[…] to provide a basis for understanding the determinants of disease and arriving at rational treatments and patterns of health care, a medical model must also take into account the patient, the social context in which he lives, and the complementary system devised by society to deal with the disruptive effects of illness, that is, the physician role and the health care system.
There is a significant difference between what Engel had in mind and what Bolton and Gillett argue for in the first chapters of the book. To illustrate, take COVID-19. If we want to know the full causal story of someone falling ill from the virus, many factors are involved: the institution of wet markets in parts of Asia, the politicized response by local and national authorities, the success and failures of lockdowns, international travel patterns, ways in which people gather and spread the virus, economic class, housing, and diets of the poorer classes—the list is of causes endless (including, one might argue, the interventions that didn’t happen). On Bolton and Gillett’s view, we need a biopsychosocial model to accommodate all these sorts of factors, besides the biochemical properties of the virus and the response of our bodies. But in the end, these are all distal causes to a virus causing a respiratory disease. Engel’s concerns were different: he thought that a full understanding of the ill person requires understanding the lived experience of the patient, the way in which the patient gives expression to it in a social and cultural context, the way in which a sick role is adopted and permitted (or forced), and so on.
Which of these two views of the biopsychosocial model should we prefer? Attention to the psychosocial causes of illness, as Bolton and Gillett instruct, will no doubt be of great help in devising public health interventions. But in the clinic, it is far from clear how relevant they are. And worse, attention to (distant) psychosocial causes is fully compatible with a clinical practice in which lived experience is disregarded, the social context in which the illness is manifested and communicated is ignored, the sick role is not recognized, and the patient–physician relationship isn’t examined. To put it bluntly: accepting multi-factorial causation is compatible with an entirely biomedical clinical practice. On Engel’s view, by contrast, one hasn’t understood the illness without paying attention to the aforementioned factors; physicians who don’t take psychosocial dimensions into account aren’t in an epistemic position to devise the best therapeutic strategy. It seems to me that Engels is entirely right about this—hence the importance of the biopsychosocial model in teaching and as a clinical tool. I worry that Bolton and Gillett’s update of the biopsychosocial model signifies a move away from what the real value of the model has been. Its value doesn’t lie in scientific validity of aetiology of specific illness, but guiding understanding and treatment of an ill person.
Admittedly, in expressing these concerns I may have juxtaposed Bolton and Gillett’s account of the biopsychosocial model too strongly with Engel’s. In the third chapter of the book, Bolton and Gillett discuss theories according to which people are embodied minds, embedded in an environment, enactive by manipulating their environments and responding to opportunities for action, and extended to the body and the environment—known as the 4E model (Newen et al. ). Minds are further claimed to be intersubjective, engaged in dynamics of recognition and political action and the exercise of control—roughly in line with Hegelian schools of thought. Discussion here is unfortunately scant, however, drawing from too many authors and traditions to really develop a coherent view. But in this chapter, one will find resources to support Engel’s original vision of the model.
In the fourth and final chapter, Bolton and Gillett return to Engel’s original concerns, claiming that the distinction between health and illness is biopsychosocial, that health conditions have to be understood in terms of the person as a whole, and that health care should focus on identifying and resolving the causes of activity limitations. These are very helpful and important reminders of the core tenets of the biopsychosocial model as Engel envisioned it and, without doubt, spell out the core lessons more than Engel did in his original articles.
In sum, the book contains a very rich, well-researched, and thoroughly philosophical discussion of the biopsychosocial model. A wide array of theories is explained in clear and accessible language, offering a good starting point for anyone interested in the foundations of biopsychosocial thinking and patient-centred medicine. The book does not shy away from addressing the philosophical problems raised by the model, even if it doesn’t always succeed in offering convincing answers. The focus on multi-factorial causality as the real content of the model is one I think we should be hesitant about. The holism and directives for patient-centred care specified in the final chapter, on the other hand, touch the heart of what the biopsychosocial model continues to offer: a valuable tool for teaching and clinical use. The publishers, Palgrave Macmillan, have made this an open access publication, and I encourage philosophers of medicine and health care practitioners alike to read this stimulating book.
Engel, G. L. : ‘The Need for a New Medical Model: A Challenge for Biomedicine’, Science, 196, pp. 129–36.
Engel, G. L. : ‘The Clinical Application of the Biopsychosocial Model’, American Journal of Psychiatry, 137, pp. 535–44.
Ghaemi, S. N. : The Rise and Fall of the Biopsychosocial Model: Reconciling Art and Science in Psychiatry, Baltimore, MD: John Hopkins University Press.
Kim, J. : ‘The Myth of Nonreductive Materialism’, Proceedings of the American Philosophical Association, 63, pp. 31–47.
Kim, J. : Supervenience and Mind, Cambridge: Cambridge University Press.
Newen, A., De Bruine, L. and Gallaghaer, S. : Oxford Handbook of 4E Cognition, New York: Oxford University Press.