The Biopsychosocial Model of Health and Disease

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The Biopsychosocial Model of Health and Disease

Derek Bolton Grant Gillett palgrave macmillan

Preface

The problem area of this essay is set within a broad trend of increasing recognition that crossdisciplinary approaches are needed for addressing the aetiology, prevention and management of diseases. The recognition of this need goes by the name of the ‘biopsychosocial model’, originally proposed by the physician and psychoanalyst George Engel in a paper published in 1977. By now, some 40 years on, the model has a reasonable claim to be the overarching framework for medicine and healthcare, invoked in clinical and health educational settings the world over. Notwithstanding its popularity, however, the biopsychosocial model has come to be seen as intellectually deficient. Recent commentary sees the biopsychosocial model as being handwaving, vague, lacking scientific validity and philosophical coherence. That the aspiring overarching framework of medicine is apparently at the same time so radically flawed signals a substantial problem in the conceptual foundations of contemporary medicine and healthcare. This is the problem we address in this book. We aim to articulate a clear biopsychosocial model, drawing on Engel’s original, but updating it in the light of substantial developments in the sciences and philosophy in the past few decades. While the task is focussed on the health sciences, it is set within the wider context of crossdisciplinary theory, research and problem-solving in contemporary life and human sciences.

Much evidence has emerged in the health sciences over the past few decades of psychosocial as well as biological factors being implicated in the aetiology, prognosis and clinical management of health conditions.

v vi PREFACE

Typically the relative involvement of the various kinds of factor depends on the specific condition, and on stage of condition. The biopsychosocial model has stood ready to accommodate this emerging evidence, a convenient depositary, but the conceptual task of clarifying the model appropriate for this new evidence is challenging. The conceptual challenge, recognised by Engel and contemporary commentary, is that there are historically deeply entrenched assumptions—physicalism, dualism and reductionism—to the effect that only material, physical and chemical causes are real, while distinctive psychological causes and social causes are impossible or incomprehensible. Against this background, the task of theorising biopsychosocial causal interactions in health and disease is non-trivial. The result we intend however is a model that can recognise psychological and social factors as being as real and as causal as muscle strength, biochemical reactions, molecular genes or brain circuitry.

Our methodology is to work with concepts and principles worked out in the sciences, but those of a fundamental theoretical status that borders into the ‘philosophical’ or even ‘metaphysical’. These latter terms capture the idea that core scientific theory is not just accumulated data, but rather guides empirical research and interprets its findings. Core theory has an æ priori quality, though in the context of shifting patterns and paradigms of knowledge, not absolute. What we customarily think of as philosophy on the other hand, and science on the other, merge together in the philosophical core of scientific theory. This was so in the mechanisation of the world-picture, which combined revolutionary science with ontological statements as to the primary causal qualities of nature, assigning cognition to an immaterial status with no or inexplicable causal power. In the radical changes that have been occurring in the life and human sciences over the past few decades we find new concepts, ontology and principles of change that do not so much solve old problems as disregard the terms in which they were constructed. For example the new models in cognitive neuroscience of embodied and embedded cognition replace the old mind/body dualism and its associated problems. New biological research programmes on genetic regulatory control of cellular metabolic processes complement but exceed the physical laws governing energy exchanges in making and breaking chemical bonds, hence effortlessly, as it were, circumventing the old idea that physics and chemistry say all there is to be said about causation. In short, the conceptual apparatus needed to theorise biology as involving a distinctive form of causation, and cognitive processes as biological, as well as

PREFACE vii in interaction with the environment, natural and social—is already in the science, as work in progress, and our purpose here is only to organise some key concepts and principles into a short core theory suitable for the biopsychosocial model of health, disease and healthcare. This core theory involves new concepts and models in the health sciences, such as those implicating chronic stress as a key mechanism linking adverse psychosocial factors to poor health outcomes.

The authors have mixed disciplinary backgrounds—DB in philosophy and clinical psychology; GG in medicine, neurosurgery, philosophy and bioethics. We have written this following many years of clinical experience, research and theorising. Biopsychosocial problem-solving is trans-disciplinary—the theory breaks down traditional boundaries.

London, UK Derek Bolton Otago, New Zealand Grant Gillett January 4, 2019

ACKNOWLEDGEMENTS

This work was supported by the Wellcome Trust [grant reference 086071/Z/08/Z]. It represents independent research part funded by the National Institute for Health Research (NIHR) Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King’s College London. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care.

Derek Bolton

CONTENTS l1 The Biopsychosocial Model 40 Years On 1.1 Doing Well—But with Underlying Problems 1.2 Locating the Content of the Biopsychosocial Model 1.3 The General Model: Biopsychosocial Ontology and Interactions References

2 Biology Involves Regulatory Control of Physical-Chemical Energetic Processes 2.1 The New Biology/Biomedicine 2.2 The Limitations of Physicalism 2.3. Current Biomedicine Is Conducive to the Biopsychosocial Model References

3 Psychology Regulates Activity in the Social World 3.1 The Psychological as Embodied Agency 3.2 Biopsychosocial Conditions of Agency 3.3 The Socio-Political: Who Gets to Control What? 3.4 General Theory of Biopsychosocial Systems References xii CONTENTS

4 Biopsychosocial Conditions of Health and Disease 4.1 Conditions of Biopsychosocial Life 4.2 Biopsychosocial Conceptualisation of Health Conditions 4.3 Locating Causes in Biopsychosocial Systems 4.4 Compare and Contrast Physical and Mental Health Conditions 4.5 Locating the Biopsychosocial Model References

Index

132 137 141

ABOUT THE AUTHORS

Derek Bolton is Professor of Philosophy and Psychopathology at the Institute of Psychiatry, Psychology and Neuroscience, King’s College London. He read Moral Sciences and was awarded a Ph.D. in Philosophy at the University of Cambridge. His subsequent professional career was in clinical psychology at the Maudsley Hospital in London. He has published numerous papers in health sciences including on genetics and treatment of obsessive compulsive disorder, as well as in philosophy of psychiatry. He is the author of An Approach to Wittgenstein’s Philosophy, Macmillan, 1979, reprinted 2013; Mind, Meaning, and Mental Disorder: The Nature of Causal Explanation in Psychology and Psychiatry, with Jonathan Hill, 2e, 2004, and What Is Mental Disorder? An Essay in Philosophy, Science and Values, 2008.

Grant Gillett is a Professor of Biomedical Ethics at the University of Otago and writes extensively on neuroethics as a sub-theme in neuro-philosophy. His professional career was in Neurosurgery and was punctuated by a D.Phil at Oxford University in philosophy of mind and metaethics. He has published in the philosophy literature on philosophy of mind and language, philosophy of medicine (particularly psychiatry), and the philosophy of medical and social sciences. He is the author of The Mind and Its Discontents, 2e, 2009; Subjectivity and Being Somebody: Human Identity and Neuroethics, 2008, and From Aristotle to Cognitive Neuroscience, 2018.

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Chapter 1

Abstract The first chapter outlines George Engel’s proposal of a new biopsychosocial model for medicine and healthcare in papers 40 years ago and reviews its current status. The model is popular and much invoked in clinical and health education settings and has claim to be the overarching framework for contemporary healthcare. On the other hand, the model has been increasingly criticised for being vague, useless, and even incoherent—clinically, scientifically and philosophically. The combination of these two points signifies something of a crisis in the conceptual foundations of medicine and healthcare. We outline some of the emerging evidence implicating psychosocial as well as biological factors in health and disease, and propose the following solution to the vagueness problem: that the scientific and clinical content of the model relates to specific conditions and stages of conditions, so that there is, for example, a biopsychosocial model of cardiovascular disease, diabetes or depression. Much the same point applies to the narrower biomedical model. However this raises the question: what is the point of having a general model? Our response is that it is needed to theorise biopsychosocial interactions in health and disease. In the light of historical prejudices against psychosocial causation deriving from physicalist reductionism and dualism, recognised by Engel and current commentators on the biopsychosocial model, this is a non-trivial task that occupies subsequent chapters.

© The Author(s) 2019 l D. Bolton and G. Gillett,

Keywords Biomedical model - Biopsychosocial model + Philosophy of medicine - Medical models

1.1 DoING WELL—BUT WITH UNDERLYING PROBLEMS

Engel’s Proposed Improvement on the Biomedical Model

In his classic paper published in 1977 George Engel proposed a new model for medicine, the biopsychosocial model, contrasted with the existing biomedical model [1]. While recognising the great advances in biomedicine, Engel argued that nevertheless the biomedical model was limited, and insufficient for many aspects of medical science and healthcare. These limitations were extensive, comprising failure to take account of the following: the person who has the illness, the person’s experience of, account of and attitude towards the illness; whether the person or others in fact regard the condition as an illness; care of the patient as a person; for some conditions such as schizophrenia and diabetes, the effect of conditions of living on onset, presentation and course; and finally, the healthcare system itself also cannot be conceptualised solely in biomedical terms but rather involves social factors such as professionalisation ({1], pp. 131-135). Engel argued that a broadening of the biomedical approach, a new biopsychosocial model, was needed to take account of all these factors ‘contributing to both illness and patienthood’

The Presumed ‘Overarching Framework’?

In his review of a recent book on the biopsychosocial model by Nassir Ghaemi [2], in The American Journal of Psychiatry, Kenneth Kendler starts with the sentence: “This book is about a very important topic— the overarching conceptual framework of our field of psychiatry” ([3], p. 999).

Whether the biopsychosocial model has this status for the rest of medicine is less clear, given the prominence of biomedicine and its biomedical model. Nevertheless, ‘the rest of medicine’ is not one thing, and the various medical specialities differ in their relative involvement with the biological, the psychological and the social. Primary care, also known as general practice or family medicine, is well-known to be much involved in psychological and social factors, and another clear example is public health. The relevant contrast here is with biomedicine, but biomedicine is not itself a medical speciality, but a particular kind of biological science-based medicine that can be applied across medical specialities, in some more than in others. Although Engel starts his paper referring to the ‘medical model’, he soon switches to ‘biomedical model’ and this is the term he uses for the contrast with his new proposed ‘biopsychosocial model’. In short it is not only psychiatry but also all the other non-biomedical aspects of medicine and its specialities that apparently require the broader biopsychosocial model.

We will review some of the health science suggesting the need for a biopsychosocial model in the next section, but first let us consider some current major trends in health, disease and healthcare that point to the same conclusion.

Engel was primarily concerned with psychosocial aspects of managing illness within hospitals, complementing the biomedical approach in hospital care. The example he discussed in detail in his 1980 ‘clinical applications’ paper was of myocardial infarction [4]. However, it has become clear in the intervening decades that managing illnesses in hospital is a particular and expensive way of providing healthcare. Illness severe enough to require hospital admission has high burden of suffering and disability, and high costs of hospital care, including biomedical investigations and treatments. It would be better all round to prevent illness altogether, or to detect and manage it earlier to prevent worsening, and also better to provide community and social care where possible to avoid or shorten hospital admissions. Implementing this last strategy involves practical psychological and social factors, such as availability of social supports or social care. The first two strategies, primary and secondary prevention, interact with psychosocial factors such as lifestyle, social capital and health literacy.

At the same time the importance of many of the areas of neglect that Engel conveniently listed under one heading—as shortcomings of the biomedical model—have been ratcheted up by diverse trends including socio-cultural changes, economics and globalisation. The voice of the service user has gained strength from civil rights and general emancipatory social changes; rising costs of healthcare in economically developed countries have focussed minds on containing costs by service reorganisations of diverse kinds; health has become globalised in many ways, such as improving health services in economically developing countries, or in the need for international policy to manage epidemics that can now spread more rapidly worldwide.

Other trends since Engel wrote that have also broadened the focus to include more than the biomedical model have to do with changing patterns of population health. Among the greatest achievements of biomedicine have been the identification, treatment and control of infectious diseases. However, and connected, the current burden of ill health in the population now includes many conditions that are not infectious diseases and which have no available complete cure—the so-called non-infectious diseases (NCDs), sometimes also called long-term conditions (LT'Cs)— such as cardiovascular disease, diabetes, recurrent depression and schizophrenia. In addition, as people live longer, for many reasons including biomedical advances, the proportion of the elderly increases, especially in the absence of immigration, and care of the elderly in hospital accounts for a high proportion of healthcare costs. In short, what biomedicine is good at no longer solves a large part of the population health burden and costs, and can contribute to rising costs by keeping us alive longer (thank you at a personal level) but at great expense—to someone, especially the younger generations. What is needed to theorise all these developments is much more complicated than biomedicine or the biomedical model were ever designed for. As well as biomedicine, what is needed is a complex mix of social science, politics, economics, environmental and social epidemiology and psychology—and no doubt more scientific specialities under development.

A further development in the decades since Engel’s papers that has added overwhelming weight to the case for a model that can encompass biological, psychological and social factors has been accelerating research on the causes of illness, the basis for primary prevention. The recent research, to be reviewed briefly in the next section, makes two things clear: first, that for many diseases, causes or risks are present from very early on, and second, that for many these causes or risks are combinations of biological, psychological and social. Prospective epidemiological studies suggest that risks for many major illnesses, physical and mental, start early in development, many in childhood, and that risks include social factors such as poverty and other forms of social exclusion, some specific family level factors such as neglect and abuse, and Jife-style factors such as exercise and diet. Findings on what have come to be called ‘social determinants of health’ were summarised and publicised for example by Michael Marmot in his 2010 Strategic Review of Health Inequalities in

England [5]. At the same time, but proceeding largely separately, there have been rapid advances in genetics. Over the past few decades many physical and mental health conditions have been found to have a genetic risk—and genetic risk starts from conception, and interacts with non-genetic factors including but not limited to psychosocial factors of the sort identified in the social epidemiological literature. In short, these sciences combined have produced a whole new dimension of the claim of the biopsychosocial model that conditions of living—as well as biological factors—may affect the onset, presentation and course of an illness.

For all these various kinds of reasons, since Engel wrote his papers some 40 years ago, the biopsychosocial model has become the orthodox overarching model for health, disease and healthcare. It is much cited and taught in healthcare trainings of all sorts and in workshops and ward rounds the world over. In simple terms it recommends to healthcare to take into account all three aspects, the biological, the psychological and the social. It is particularly useful in psychology and social work healthcare professions, and in medical practice that has to deal with the psychological and the social as much as the biomedical, primary care (family medicine) being the clearest example [6], and in-hospital medical training that emphasises the importance of a comprehensive management plan. In all these contexts the biopsychosocial model easily wins, facilitating identification and integration of different aspects of care aimed at different aspects of the patient’s life, disease and management. To illustrate further good fit with much current practice, the biopsychosocial model obviously aligns with the rationale of multidisciplinary teams, and with the increasing recognition of the value of the service user’s views in providing good and effective healthcare.

Given the prominent status and use of the biopsychosocial model, it is clearly of great importance that the model is clear and robust. At this point, however, there is a very large problem, because there have been increasing charges in the medical literature that in fact the biopsychosocial model—popular and accommodating as it may be—is far from being clear and robust, but is in fact deeply flawed.

But Lacks Content, Validity and Coherence

Engel’s biopsychosocial model has long been criticised for having various kinds of limitation, along with suggestions for improvements (e.g. [7-9]). Increasingly, however, there have been more radical criticisms. Such radical criticisms are of two main types: first, that the model lacks specific content, is too general and vague, and second, that it lacks scientific validity and philosophical coherence. Given the popularity of the biopsychosocial model and its presumed status as overarching framework for medicine and healthcare, such radical criticisms signal significant underlying theory problems.

The first broad heading of criticism is well argued by Nassir Ghaemi, a psychiatrist at Tufts, in his 2010 book with the telling title: ‘The Rise and Fall of the Biopsychosocial Mode? [2]. Ghaemi argues that the model is vague, too general, tells us nothing specific of value, hence is inefficient and sometimes distracting; it ‘gives mental health professionals permission to do everything but no specific guidance to do anything’ ([2], p. 82). The way Ghaemi tells the story, the biopsychosocial model arose in the context of competing general views about illness, favouring one or other of the social, the psychological/psychoanalytic and the biological. These general views—one might call them ideologies without criticism— were views of the whole domain of illness, offering general accounts, discriminating not much between kinds of case to which they applied and kinds of case to which they did not. Ghaemi interprets the biopsychosocial model as an elegant—if problematic and ultimately unviable— solution to these ideological conflicts: the unseemly turf wars could be ended, a truce could be declared, if all the participants won, if they were not really in opposition at all, but were in fact all true general accounts of illness and healthcare in all their aspects. The problem whether the cause of illness, and hence in theory its prevention and treatment, is biological, psychological or social is solved, because the answer is ‘all three’ ([10], p. 3; [2], ch. 6).

It has to be said that this line of thought is not apparent in Engel’s main papers [1, 4]. Ghaemi does however quote a characterisation of the biopsychosocial model from another of Engel’s papers consistent with presumed generality: ‘all three levels, biological, psychological, and social, must be taken into account in every health care task’ ({11], p. 164; [10], p. 3). This claim Ghaemi understands as meaning that the three levels ‘are all, more or less equally, relevant, in all cases, at all times’ ([10], p. 3). In these quotes one can see the point of the allegations that the biopsychosocial model is a slogan, too vague to be of any use. And moreover, when pinned down, more than likely just wrong, counter-evidenced exactly by the successes of biomedicine, in which biological factors alone adequately explain diseases and treatments, such as bacterial l1 THE BIOPSYCHOSOCIAL MODEL 40 YEARSON 7 infections and anti-biotics cures. Effective biomedicine is an anomaly for any general claim to the effect that ‘everything is biopsychosocial’, an obvious point that warrants repetition (e.g. [2, 12]).

So, the charge is that the biopsychosocial model is vague without specific content. If, on the other hand, the model is firmed up to a very general proposition about the general relevance of all three kinds of factors, it is likely to be just false, exactly because of biomedicine. Faced with this obvious enough fact, a possible move is retreat to vagueness, but at the cost of content, as highlighted increasingly by critical commentary.

As mentioned above when illustrating the current important status or aspirations of the biopsychosocial model, Kenneth Kendler opens his review of Nassir Ghaemi’s book with the statement that its topic is very important, the overarching conceptual framework of psychiatry ([3], p. 999). In his review Kendler goes on to quote Ghaemi’s negative conclusion, ‘The BPS model has never been a scientific model or even a philosophically coherent model. It was a slogan...’ ([2], p. 213), and comments: ‘While the reader may think this a little harsh..., I think he is substantially correct in this assessment’ ([3], p. 999). On the other hand, Kendler ends his review with a reminder of the importance of the biopsychosocial model as a teaching tool in family medicine, concluding: ‘While I agree with Ghaemi that the Biopsychosocial model has been a failure as a scientific paradigm, it probably continues to serve a useful clinical and teaching function in psychiatry and medicine’ ([3], p. 999). Kendler correctly identifies the major tension here: the biopsychosocial model is a useful tool for clinical and teaching functions, but apparently lacks scientific validity and philosophical coherence.

But then probably all cannot be problem free on the teaching front either. Here is Chris McManus, Professor of Psychology and Medical Education at University College London, reviewing an earlier edited book on biopsychosocial medicine in The Lancet ([13], p. 2169):

Biopsychosocial medicine’s challenge is to transcend the vague, aspirational inclusivity of its name, and to create a model that truly merits being called a model, and is properly explanatory and predictive ... Arm-waving and the inclusion of everything ultimately says and does little of practical consequence.

Ghaemi, Kendler and McManus all basically agree in their negative assessments of the biopsychosocial model.

Given the popularity of the biopsychosocial model, its use in teaching and the clinic, its presumed status as the overarching framework for psychiatry and perhaps for medicine generally, such authoritative negative assessment signals significant problems at the conceptual foundations.

We believe that these two kinds of charge put to the biopsychosocial model, querying its content, validity and coherence, are cogent, but can be met. What they signal is not the end of the model—witness the fact that it persists, for good reasons already indicated—but the need to rethink and reinvigorate it. The answer to the content problem, we suggest, is that the content lies in scientific and clinical specifics, not generalities. This is proposed in the next section, beginning with a brief review of the emerging basic and clinical science supporting the biopsychosocial model. This response to the content problem, however, immediately raises the question: if the content of the biopsychosocial model lies in specifics, what is the point of the general model? We suggest that this question relates to core scientific theory, at the place where it merges into philosophy, and is therefore here that the problem of scientific validity and philosophical coherence is to be addressed. We define this problem in Sect. 1.3, and address it in detail through subsequent chapters.

1.2 LOCATING THE CONTENT OF THE BIOPSYCHOSOCIAL MODEL

Emerging Evidence of Psychosocial Causation

Just as the biomedical model is of interest because of the substantial and well-established evidence base of biomedicine, so the biopsychosocial model warrants attention insofar as there is evidence of psychological and social as well as biological factors in health and disease. There has been an accumulation of such evidence in recent decades, and before moving the main theoretical argument forwards, we pause to review some of it. This review carries a health warning! It is uncritical and unsystematic; we have usually not distinguished strength of evidence of the studies cited below (uncontrolled to randomised controlled and replicated), nor commented on other aspects of methodological strengths (such as sampling strategies and sample size), nor on conflicting and uncertain results, nor have we employed a systematic literature search strategy. Many of the papers cited are reviews, more or less systematic. The purpose here is only to orientate the unfamiliar reader to wide range of research that has supported on-going interest in the interplay of biological, psychological and social factors in health and disease and hence the biopsychosocial model.

Over the past few decades the picture that has emerged for causes of disease onset, especially for the non-communicable diseases, also known as the LTCs, is one of complex, multifactorial causation, involving many risk factors of relatively small effect, affecting multiple outcomes. The recent research on social factors as causes or risks for poor health—the so-called ‘social determinants of health’—is probably the most well-known, new face validation of the need for a broad biopsychosocial model. Among the most influential social epidemiological research programmes are the Whitehall Studies of British civil servants, led by Michael Marmot [14-16]. These longitudinal cohort studies found robust correlations between variance in incidence for a wide range of health conditions—coronary heart disease, premature mortality, some cancers, lung disease, gastrointestinal disease, depression, suicide, sickness absence, back pain and general feelings of ill-health—and civil service grade. The social gradient in health—the correlation between indices of social status and health outcomes—is now well-established; much is now known about the social determinants of health [17, 18], and something like the biopsychosocial model has to be invoked in order to comprehend it. As typically for epidemiology, most findings on the social gradient in health come from association studies only, retrospective or prospective. Establishing causation is more complex, using such as controlled cohort studies, natural experiments or animal models.

Other large research programmes have investigated associations between adverse psychosocial exposure in childhood and later health outcomes. A landmark programme is the Adverse Childhood Experiences Study (ACE Study) in the United States, carried out by Kaiser Permanente and the Centers for Disease Control and Prevention. The ACE study has demonstrated associations between adverse childhood experiences, such as physical and emotional neglect and abuse, and a large range of physical as well as mental health outcomes (e.g. [19]).

Lifestyle factors, comprising behaviours and associated beliefs, attitudes and values, have been increasingly implicated as risks, or conversely as protective factors, for a wide range of physical health conditions [14, 18]. For example risk factors for some cancers and cardiovascular disease include such as smoking, alcohol use, diet, exercise and chronic stress. Lifestyle factors can be covered under the same heading as social factors, or separately. Either way, lifestyle factors interact strongly with social context, reflecting Engel’s insight that the person is essentially within a social context: diet for example, depends to some extent on choice, but also on what is available and affordable; stress—to be considered in Chapter 4—depends on individual characteristics but also on task demands and available resources.

Lifestyle and psychological factors can be distinguished: the former are behavioural, while the latter, such as beliefs, attitudes and values, are mental. At the same time they are closely linked. One reason is that psychological factors motivate lifestyle, but there is also a general linkage between our psychology and our behaviour, namely, that we respond to reality at it appears to us, at any given time, to be. We pick this up as a theoretical point in more detail later, in Chapter 3 (Sect. 3.1, heading “Mind Is Embodied”). In the present context it appears in evidence suggesting that it is not objectively measured social status but social status as perceived, so-called ‘subjective social status’ that accounts for more of the variance in health outcomes (see e.g. [20, 21]). This interesting finding becomes part of the complex jigsaw puzzle of biopsychosocial aetiology.

Over the same past few decades that evidence for psychosocial factors in health and disease has been accumulating, so also has evidence of genetic effects. For some health conditions such as Huntington’s chorea, and some cancers, there are massive genetic effects, but for the majority of health conditions, the proportion of population variance attributable to genetic influence is much less than 100%, the picture being rather of relatively small effects of multiple genes, with the remaining variance attributable to non-genetic, environmental factors. Combining these broad kinds of research programmes presents a biological-psychological-social and-environmental picture, and new epigenetics is likely to help explain how the various kinds of factor interact. These issues are taken up in Chapter 3, Sect. 3.4.

Post-onset course of disease raises different causal questions: what are the processes determining course, for example, progression, stability, fluctuation or recovery? Treatment effects are a special case, assessed using a range of designs including randomised controlled trials. There has been accumulating evidence from randomised controlled treatment trials since the late 1970s of treatment effects of psychosocial interventions on some mental health conditions. Among the first was a randomised controlled trial of cognitive behaviour therapy for depression

1 THE BIOPSYCHOSOCIAL MODEL 40 YFARSON ll published by Beck etal. [22] showing effectiveness, but further, the same effectiveness as for anti-depressant medication. In effect this trial showed that a psychological intervention could achieve the same result as a biomedical intervention, and it paved the way for accelerating developments of tested psychological treatments for a wide range of mental health conditions and the translation of these into national health service provisions. There are complications, as always, for example, as to the extent to which psychological therapy outperforms pill placebo control, but the principle that some psychotherapies help some mental health conditions has been established (e.g. [23]).