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Journal of Evaluation in Clinical Practice ISSN 1365-2753
Causal explanatory pluralism and medically unexplained physical symptoms Michael Cournoyea BSc1 and Ashley Graham Kennedy PhD2 1
PhD Candidate, Institute for the History and Philosophy of Science and Technology, University of Toronto, Toronto, ON, Canada Assistant Professor of Philosophy, Wilkes Honors College, and Assistant Professor of Clinical Biomedical Science (secondary), Charles E. Schmidt College of Medicine, Florida Atlantic University, Jupiter, FL, USA
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Keywords diagnosis, explanation, patient-centred care, person-centred medicine Correspondence Mr Michael Cournoyea Institute for the History and Philosophy of Science and Technology University of Toronto Toronto, Ontario M5S 1K7 Canada E-mail: [email protected]
Abstract In this paper, we propose a methodology for investigating medically unexplained physical symptoms (MUPSs). These symptoms are common in both primary and specialist medical practices, but are poorly understood. Currently, MUPSs are diagnosed via non-explanatory labels. However, we show that explanatory diagnoses are preferable to non-explanatory syndromic diagnoses because they bring both epistemic and therapeutic benefits to patients and their providers. Thus, we advocate a methodology of causal explanatory pluralism in the diagnostic workup and clinical management of MUPSs.
Accepted for publication: 29 July 2014 doi:10.1111/jep.12238
Introduction Medically unexplained physical symptoms (MUPSs1) are shockingly common in both primary and specialist practices; estimates of patients that present with MUPS range from 25% to 70%, with higher percentages among certain demographics and those that present to specialists [1,2]. These symptoms range from acute to chronic, mild to severe, and explanatorily probabilistic to impenetrably obscure. Some chronic collections of symptoms have been labelled as syndromes, such as irritable bowel syndrome, multiple chemical sensitivity, fibromyalgia, or chronic fatigue and immune dysfunction syndrome. Patients that exhibit these syndromes often 1
In the medical literature, MUPSs are sometimes referred to simply as MUS (medically unexplained symptom) or even ‘somatization’. We prefer the acronym MUPSS (medically unexplained physiological signs/ symptom), but have opted to use MUPS for consistency with the literature. We prefer to use ‘physiological’ rather than ‘physical’ because it denotes a more accurate class of signs/symptoms and we include ‘signs’ to acknowledge that signs can be unexplained. Medical signs such as hypertension are often taken to be objective facts, clearly explained; however, while it may be clear what a sign is, it is not always clear why a sign is present. In addition, ‘MUPS’ is used interchangeably (and sometimes ambiguously) to refer to a category of illnesses, illnesses themselves (IBS, CFIDS, etc.), or single signs/symptoms that remain unexplained (lower back pain, fever, etc.).
Journal of Evaluation in Clinical Practice (2014) © 2014 John Wiley & Sons, Ltd.
move continuously between medical specialists and receive a variety of uncertain diagnoses [3–5]. The medical literature on MUPS is overwhelming, but from a philosophical perspective, little has been written on the topic, leaving open the questions of how MUPSs are (and should be) explained and how and why medical ontologists exclude MUPS.2 Since MUPS refers to several syndromes, one strategy might be to address each syndrome separately rather than attempting to find a unified account of MUPS. In contrast, we aim to address the methodological question of how MUPS should be explained in general, proposing that MUPS diagnoses should be approached pluralistically.
The diagnostic ideal It is uncontroversial in the medical literature that the ideal diagnosis is a biomedical causal explanation [7,8].3 This is generally arrived at via a process of observation, testing and an often complex combination of deductive, inductive and abductive 2
See Eriksen et al. [6] for a discussion of how dispositional ontologies may better accommodate MUPS. 3 This is not to say that this is the only type of diagnosis. As we will discuss in a later section, some diagnoses are syndromic diagnoses and do not posit causes. However, the ideal diagnosis in current medical practice is a causal explanation – whether topologic or (preferably) aetiologic.
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reasoning [9]. Such a diagnosis posits a physiological cause for a set of physical signs and symptoms.4 A physical sign is something that can be observed directly by the doctor via testing and/or physical examination; a physical symptom is a patient reported discomfort or abnormality. For example, the diagnosis of strep throat, a bacterial infection caused by Streptococcus pyogenes, is a biomedical causal diagnosis that makes use of both physical signs (e.g. a positive Strep culture) and symptoms (e.g. a painfully sore throat). Thus, in the case of a sore throat coupled with a positive strep culture, a strep infection is said to be the physiological cause of the physical signs and symptoms. Knowing this physiological cause allows the clinician to target and treat the causal process; in turn, this will hopefully lead to the resolution of the patient’s discomfort. Treating patients by intervening on physiological causes is the primary goal of biomedicine as currently practised. For example, penicillin is the first-line treatment for strep throat, which, when administered in the correct dosage for the appropriate length of time, does in fact lead to a full resolution of the signs and symptoms in the vast majority of patients because it targets the physiological cause of the illness. Of course, not all known physiological causes of physical signs and symptoms have available medical treatments. This is not a concern we will address here. Instead, we are interested in how contemporary medicine attempts to explain physical signs and symptoms with an unknown physiological cause. While strep throat is an uncontroversial example of a biomedical causal diagnosis (with a readily available and effective medical treatment), many diagnoses fall short of this ideal. In the most challenging cases, patients receive ‘syndromic diagnoses’ that lack a causal explanation, as is the case with MUPS where explanatory diagnoses are not available. Syndromic diagnoses are agnostic concerning underlying aetiological or structural explanations. This not only means that the cause of these signs and symptoms is unknown, it also usually means that it is not known how to treat the disorder in question.
Diagnosis by exclusion Most diagnoses of unknown cause are arrived at via the process of diagnosis by exclusion [10,11]. Diagnosis by exclusion proceeds as a part of the process of differential diagnosis, where a doctor will come up with a list (or ‘differential’) of probable diagnoses. The doctor decides what to put in a differential by looking at pieces of positive evidence (or evidence for certain conditions). Then, when deciding what to exclude from a differential, a doctor might consider alternatives using negative evidence (or evidence against certain conditions). To see how this process works, consider the following case study as an example:5 Brad is a 43-year-old motivational speaker and married father of four young children who was entirely well until six months ago. Brad now presents with the chief complaints of persistent fatigue, recurrent flu-like symptoms and difficulty concentrating. He says that whenever he ‘pushes’ himself, he experiences terrible exhaustion, muscle pain, aching in various joints, soreness in the neck, and burning eyes. These 4
There can of course be more than one physiological cause. The italicized portion of this section was adapted from the ‘Case Studies’ section of http://www.cfids.org. 5
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symptoms may last one or two days, then subside somewhat. He has become clumsy and bumps into things around the house. He notes new difficulties with memory, simple decisions, basic calculations, and word searching. He has noticed increasing mental confusion, distractibility and disorientation in familiar surroundings. His complaints include generalized weakness, ‘restless’ legs and jerking at night, night sweats, tender glands in the neck and a feverish feeling despite subnormal body temperatures. His sleep is shallow and disrupted, and he wakes up feeling worse than when he went to bed. Brad awoke one morning with fever and a ‘terrible flulike feeling.’ He consulted his primary physician when he did not improve over several days. Initial evaluation revealed mildly elevated liver function and a slightly positive antinuclear antibody (ANA) test, but otherwise the examination and laboratory testing did not reveal the cause of his illness. He has been essentially housebound for the past six months, but is able to handle most of his personal activities of daily living. He has been physically active for up to four hours at a time ‘safely’, but some days he has been unable to do anything. Brad’s past medical history is remarkable only for herniorrhaphy, and repair of a severed nerve. There is no history of hair loss, sun sensitivity, recurrent rash, recurrent mouth ulcers, Raynaud’s phenomenon, or kidney disease. There has been no swelling, heat, or redness at the joints. There has been no abdominal pain or recurrent diarrhea of note. Brad reports a travel history, recalling a backwoods camping trip in Wisconsin with the family sometime prior to the onset of his symptoms. Given this history and set of symptoms, Brad’s physician might reasonably come up with the following differential: 1 A collagen vascular disorder such as lupus. 2 A rheumatological disorder such as rheumatoid arthritis (RA). 3 An infectious disease such as Lyme disease or a virus. 4 Chronic fatigue and immune dysfunction syndrome (CFIDS). Let us suppose that a repeat ANA is negative, making the diagnosis of lupus unlikely. Similarly, a workup for RA is unremarkable. If this is the case, the doctor might then test for some infectious causes of Brad’s illness such as cytomegalovirus, Epstein–Barr virus or Lyme disease.6 Supposing that these laboratory studies are also negative, the results together constitute negative evidence for the diagnosis (by exclusion) of CFIDS. In other words, if the other diagnoses in the differential are ruled out, then a diagnosis of CFIDS will likely be made, if positive evidence for the syndrome is also present. To meet the case definition criteria for the positive evidence for CFIDS, a patient must have had persistent or relapsing fatigue for more than 6 months with no pre-existing illness to explain the debilitating fatigue. In addition, the patient must have at least four of eight symptom criteria: (1) cognitive symptoms; (2) sore throat; (3) tender cervical/axillary lymph nodes; (4) myalgias; (5) arthralgias; (6) headache (of a new type or severity); (7) unrefreshing sleep; or (8) post-exertional malaise. 6
Clearly, it is not possible to rule out all infectious agents in this case, or others like it (there are more than 60 infectious conditions that share symptoms with CFIDS). Generally, no attempt is made to do so. Instead, the doctor tests for certain likely illnesses (where likelihood is determined by the doctor) and if these tests turn out to be negative the category of ‘infectious agent’ is eliminated from the differential.
© 2014 John Wiley & Sons, Ltd.
M. Cournoyea and A.G. Kennedy
If a patient, like Brad, meets four of these criteria and has negative laboratory results, he or she will very likely be diagnosed with CFIDS.7 However, this diagnosis, and the method by which it is obtained, is problematic for at least two reasons. Firstly, because it is never feasible to rule out all possible alternative diagnoses, any diagnosis arrived at via the process of differential diagnosis is inherently uncertain. Secondly, and more problematically, when a causal explanation for a set of signs and symptoms is not described as part of the diagnostic process, as in the case of a syndromic diagnosis, the diagnosis lacks the epistemic and therapeutic benefits that are conferred with an explanation (which we discuss in the section The benefits of an explanatory diagnosis). Syndromic diagnoses of MUPS are lacking for these reasons. If causal physiological diagnosis is the gold standard in contemporary medicine, then why are syndromic diagnoses ever made? The most common reason for a syndromic diagnosis is pragmatic: once a diagnosis has been made, a doctor will then stop investigation into the cause of the patient’s illness. This means that time and money will not be spent on further investigation into the cause of the patient’s illness, even though the illness remains underdetermined.8 However, the pragmatic gain in such instances is often outweighed by epistemic and therapeutic losses. In what follows, we argue that causal diagnoses are preferable to syndromic diagnoses for both epistemic and therapeutic reasons.9 Because of this, we argue that causal explanatory diagnoses should be pursued in MUPS via a methodology of explanatory pluralism, even when biomedical causal mechanistic diagnoses, specifically, may not be available. 7
Or diagnosed with a psychosomatic disorder. One problematic use of diagnosis by exclusion occurs when a doctor concludes that a patient has a psychiatric illness when ‘he or she is unable to find anything that would normally be expected in a workup for somatic diseases, x, y, z, etc.’ [12, p. 7]. Of course, psychiatric diagnoses should not be made based on negative evidence alone: ‘The proper diagnosis of both physical and psychiatric illnesses requires the presence of clearly defined signs and symptoms consistent with the diagnostic category’ [12, p. 7]. Unfortunately, many MUPSs are misdiagnosed as psychiatric illnesses. 8 Clinical underdetermination occurs when no justifiable choice can be made between two or more rival diagnoses in a differential, given the available evidence. We might suspect that Brad has a viral infection, for example, and outline a differential of several viral candidates; before we perform viral-specific tests; however, the available evidence is insufficient to justify a viral-specific diagnosis. Since we cannot causally explain Brad’s illness at this stage, we cannot give Brad a causally specific diagnosis. This is always the case with MUPS. If no available tests can causally explain Brad’s illness, then he is given a syndromic diagnosis (such as CFIDS) that is, by definition, underdetermined. Consider an analogy. If an optical anomaly is discovered on a deep space telescope, we might not know whether the anomaly is a new star, a mechanical glitch, or an uncanny smudge on the telescope’s lens. Without further evidence, any belief we might have about the anomaly’s true cause is underdetermined by the available evidence. We might even give the anomaly a provisional label and apply this provisional label to similar anomalies. As with MUPS, simply labelling the anomaly is a diagnostic last resort. 9 The pursuit of causal mechanistic explanatory diagnoses is always preferable to settling for syndromic diagnoses, especially when such explanatory diagnoses offer plausible accounts for a condition. This does not imply that every explanatory diagnosis will be better than a syndromic diagnosis, since explanatory diagnoses may be false and potentially harmful. Solid clinical judgement is essential to deciding whether explanatory diagnoses may produce more epistemic and therapeutic harm than an alternative. Thanks to an anonymous reviewer for this clarification.
© 2014 John Wiley & Sons, Ltd.
Causal explanatory pluralism and MUPS
Causal explanations in biomedicine Causal diagnoses in biomedicine aim to explain physical signs and symptoms in terms of either structural causes or pathophysiological mechanisms. These two types of causal diagnoses are not mutually exclusive. For example, blurred vision and headache might be explained causally in terms of a (structural) brain lesion, which, in turn, might be caused by a (mechanistic) cancerous process. A mechanistic explanation is nearly always more fundamental than a topological or structural one and as such is considered the gold standard of medical diagnoses.10 In the case of MUPS, by definition, no causal explanatory mechanism has been identified for the disorder in question. This does not mean that causal explanatory strategies are not being employed to address MUPS. For instance, Van Ravenzwaaij et al. [14] described nine explanatory models for MUPS, each offering a unique causal mechanistic theory. In their review, they described models from 19 articles drawn from the PubMed and PsycINFO databases (between 2005 and 2010). In this list, there are physical explanations (immune system sensitization theory, endocrine dysregulation theory, autonomic nervous system dysfunction theory and abnormal proprioception theory), psychological explanations (somatosensory amplification theory, sensitivity theory) and hybrid explanations (sensitization theory, signal filter theory and an illness behaviour model). These models remain quite theoretical and Van Ravenzwaaij et al. do not suggest that they apply to particular MUPS or to MUPS more broadly. The strength of these models is in offering causal mechanisms that may help to answer context-specific questions (as outlined in the section An argument for explanatory pluralism). As such, they have the potential to bring epistemic and therapeutic benefits to patients and providers that syndromic diagnoses cannot and do not bring.
The benefits of an explanatory diagnosis As we have seen, MUPSs are non-explanatory, syndromic diagnoses that serve only as optimistic placeholders for future causal explanations. While syndromic diagnoses do not confer the full epistemic and therapeutic benefits of explanatory diagnoses, they can give patients hope concerning their conditions [1]. Explanatory diagnoses, on the contrary, provide understanding to both patients and clinicians. They can do this even in cases in which they are incomplete or only partially correct. According to Machamer et al. [15, p. 21]: The understanding provided by a mechanistic explanation may be correct or incorrect. Either way, the explanation renders a phenomenon intelligible. Intelligibility arises not from an explanation’s correctness, but rather from an elucidative relation between the explanans (the set-up conditions and intermediate entities and activities) and the explanandum (the termination condition or the phenomenon to be explained).
10 We adopt the widely applicable account of mechanisms outlined by Illari and Williamson: ‘A mechanism for a phenomenon consists of entities and activities organized in such a way that they are responsible for the phenomenon’ [13, p. 130].
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Thus, even partially explanatory diagnoses can confer benefit by making the disease intelligible to the patient and the provider, and by allowing clinicians to develop treatments and outline prognoses. In other words, causal mechanistic diagnoses are sought because pathophysiological mechanisms render diagnoses more satisfying, convincing and fruitful [16].11 While Gijsbers [17] argued that non-explanatory, classificatory theories can lead to intelligibility, we doubt that this is the case with syndromic classifications. While syndromic diagnoses help to build patient communities, fuel advocacy and encourage research, they do not unify illnesses intelligibly. Syndromic diagnoses are useful only as temporary placeholders. Explanatory diagnoses, on the contrary, answer the question of why (physiologically) a patient has a disease by connecting the patient’s signs and symptoms to the disease. Prior to an explanatory diagnosis, the patient is already keenly aware of his signs and symptoms, but he does not understand why or how they connect to an aetiology. According to Strevens, to understand why is to have an ‘intimate acquaintance with the structure of the explanation’ [18, p. 5] such that signs and symptoms are structured into an aetiology; this is exactly what is missing in non-explanatory, syndromic diagnoses. In cases of MUPS, patients may understand that they have a certain set of signs and symptoms, but they (and their clinicians) do not understand why they have them.12 Because of this, they cannot glean the full epistemic and therapeutic benefits that are available from explanatory diagnoses. These benefits are separate from the therapeutic benefits of any medical treatment developed from such a diagnostic explanation. In other words, the understanding derived from an explanatory diagnosis is therapeutic to patients in its own right. Patients that understand why they have certain symptoms get better faster than patients who do not. Van Ravenzwaaij et al. [14, p. 229] highlight this in their qualitative literature review, writing that: Plenty of doctors think in terms of action and reaction, while the explanation of symptoms in itself might be the most important intervention for patients with MUPS. Kirmayer et al. [1] also noted the importance of meaning-making and narrating distress in their intensive interviews of 18 CanadianVietnamese immigrants who presented with MUPS. In their ethnographic interviews, participants felt some alleviation when they ‘were able to provide a meaning for their symptoms – whether by referring to a biomedical diagnosis, folk label, or explanatory model’ [1, p. 667]. Those that could not explain their conditions using a biomedical or cultural model felt ‘misled and let down’ in a ‘semantic no man’s land outside social consensus and collective meaning’ [1, p. 667]. That an explanation can be a therapeutic tool speaks to the virtue of understanding in the medical encounter and the importance of pursing correct explanatory diagnoses. If understanding is both an epistemic virtue and a therapeutic tool, then it becomes evident why MUPSs are deeply unsettling to patients and clinicians alike. 11
We should emphasize that causal mechanistic explanations bestow such benefits, but these explanations need not be reductionistic; we leave a discussion of non-mechanistic explanations to future work. 12 We do not wish to make the claim that any answer to a ‘why’ question is a good one. Certainly, accurate diagnoses are preferable to inaccurate ones. However, as we have already noted, even incomplete or partial explanations can bring benefits that mere labels cannot.
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An argument for explanatory pluralism We have seen that explanatory diagnoses can confer epistemic and therapeutic benefits both to patients suffering from MUPS and to their health care providers. In this section, we will argue that explanatory pluralism is the most appropriate explanatory methodology for addressing MUPS in the clinic. We advocate a version of pluralism outlined by De Vreese et al. [19], a non-integrative methodological explanatory pluralism that privileges neither reductionism nor holism: [. . .] methodological explanatory pluralism consists in the claim that the best form and level of explanation depends on the kind of question one seeks to answer by the explanation [19, p. 374]. De Vreese et al. [19] conceived explanatory levels as incommensurable and non-supervening layers of a complete explanation (e.g. physiological and socio-economic explanations for obesity). The aim of explanatory pluralism is to find explanations that provide the most adequate, efficient and accurate information, given the explanatory questions and context. Although De Vreese et al. [19] conceived this methodology as beneficial in the research setting, we think that its benefits also extend to the clinical diagnostic management of MUPS. Non-integrative explanatory pluralism does not attempt to (1) integrate pluralistic explanations (to avoid cumbersome explanations); (2) make metaphysical claims about pluralism (as a theory of explanation); nor (3) privilege one explanatory strategy over another (i.e. it is pluralistic). This form of explanatory pluralism does not imply that any explanation goes, nor that we need to be anti-realists about MUPS. If we ask ‘Why does Brad have CFIDS?’, we need to be more specific about the aims of such a question, and ultimately we may not come to one unificatory explanation of Brad’s CFIDS, even though we may be able to answer some of the why questions concerning his situation. Consider the three questions that De Vreese et al. [19] outlined using Brad’s CFIDS: ‘Why did Brad develop CFIDS?’ can be separated into: 1 Why did Brad, who has characteristic A, develop CFIDS, while Jamie, with characteristic A′, did not? 2 Why did Brad with behaviour B develop CFIDS, while Casey with behaviour B′ did not? 3 Why did Brad living in country C develop CFIDS, while Dylan in country C′ did not? The three questions are elaborations and specifications based upon Van Fraasen’s [20] erotetic model of explanation (i.e. a theory of why-questions). Each question addresses a different relevant context: (1) micro-reductive; (2) micro-non-reductive; and (3) macro-holistic [19]. De Vreese et al. [19] emphasized that each question has the potential to yield an adequate, efficient and accurate answer without reducing the other questions. We may be able to answer (1) without (2) or (3), for example, and in doing so provide a partial explanation for Brad’s CFIDS. The explanatory models proposed by Van Ravenzwaaij et al. [14] may help to answer some of these questions. For example, endocrine dysregulation might offer a micro-reductive causal explanation for Brad’s CFIDS (as compared to Jamie’s CFIDS) that is adequate, efficient and accurate, even though it does not necessarily explain CFIDS more broadly. Treatment that intervenes on the hypothalamus–pituitary– adrenal (HPA) axis might be effective for Brad, though not Jamie, even if it does not completely alleviate Brad’s CFIDS.
© 2014 John Wiley & Sons, Ltd.
M. Cournoyea and A.G. Kennedy
Answers to these questions allow us to understand why Brad developed CFIDS in these specific explanatory contexts. As Kellert et al. [21, p. xiv] noted in their description of the pluralistic stance, inquiry ‘typically represents some aspects of the world at the cost of obscuring, or perhaps distorting, other aspects.’ Helen Longino [22] likewise advocated for pluralism in explanations of behaviour, where different approaches yield partial knowledges that compose ‘a nonunifiable plurality’ (p. 111). Explanatory pluralism is not merely a pragmatic compromise when complex cases defy explanation; such pluralism allows us to understand why more adequately, efficiently and accurately in each relevant context with the ultimate aim of discovering causal explanations. This approach does not offer a single, clear aetiology, but it does aim for a causal explanation. In practice, this approach encourages doctors to focus on specific ‘why’ questions and their answers, rather than resorting to syndromic diagnoses. Even medically explained diseases can benefit from a culture of explanatory pluralism [23]. Fortun et al. [24] recommended explanatory pluralism in tackling the ‘complex dynamics’ of asthma, as ‘modern biomedical culture expects pluralities to be reduced, “mysteries” to be cleared up, with straightforward and preferably singular explanations, after sufficient rational effort has been expended’ (p. 330). They highlight Tim Brookes’ [25] autobiographical account of asthma as he searched for the cause of his illness, feeling that ‘this was what was needed to care for, if not cure, himself’ [25, p. 326]. However, finding the cause of an illness is not always possible, nor is it strictly necessary, even from a treatment perspective. In some cases, finding a cause can be enough – from both an epistemic and a therapeutic standpoint. Engel’s biopsychosocial model may seem helpful for integrating the layered factors in our proposed pluralism. Engel’s goal was to ‘re-humanize’ biomedicine by considering the psychological and social factors essential to illness [26]. Yet Engel’s proposal leads to cumbersome triple diagnoses. Butler et al. [27] argued that the problem with Engel’s model, specifically when addressing MUPS, has historical precedent in ‘the analytic philosophical tradition to break down complex phenomena in the hope of finding meaning in the simpler constituents (reductionism)’ [27, p. 219]. They advocate an ‘interpretive approach’ that engages with patients’ experiences as ‘phenomena to be interpreted’ [27, p. 220]. We will not reiterate the many challenges to Engel’s model here (i.e. difficulties separating these components and integrating them distinctly) but it is important to note that Engel’s attempt at methodological pluralism points to the problem (i.e. reductionist biomedicine) but not to a satisfactory solution. Our solution to this problem is to suggest a methodological approach of explanatory pluralism in the diagnostic workup of MUPS. This methodology also encourages clinicians to refrain from making unjustified psychiatric diagnoses in cases of MUPS. While ‘the number of medical diseases that can present with psychotic symptoms is legion’ [28], it is of course important in any diagnostic workup to differentiate between primary and secondary psychiatric symptoms. This is especially important in cases of MUPS: if psychiatric ‘diagnoses’ are too quickly given in these cases, it causes premature closure into causal investigations, thereby reducing the chance of arriving at an accurate causal diagnosis. While we do not wish to argue that psychiatric diagnoses are never appropriate in cases of MUPS, it is important for clinicians to
© 2014 John Wiley & Sons, Ltd.
Causal explanatory pluralism and MUPS
remember that they should be made only when the presenting evidence is sufficient. In summary, as we have seen, causal diagnoses carry therapeutic and epistemic benefits for both patients and clinicians – even when they do not lead directly to the treatment for the conditions they describe. Because of this, they ought to be pursued in MUPS.
References 1. Kirmayer, L. J., Groleau, D., Looper, K. J. & Dominicé, M. (2004) Explaining medically unexplained symptoms. Canadian Journal of Psychiatry, 49 (10), 663–672. 2. Reid, S., Wessely, S., Crayford, T. & Hotopf, M. (2001) Medically unexplained symptoms in frequent attenders of secondary health care: retrospective cohort study. British Medical Journal, 322, 1–4. 3. Atkins, C. G. K., Brownell, K., Kornelsen, J., Woollard, R. & Whiteley, A. (2013) Silos of silence, stress, and suffering: patient and physician experiences of MUPS and diagnostic uncertainty. AJOB Neuroscience, 4 (3), 3–8. 4. O’Rourke, M. (2013) What’s wrong with me? The New Yorker, 26 August 2013. Available at: http://www.newyorker.com/magazine/ 2013/08/26/whats-wrong-with-me (last accessed 22 February 2014). 5. Page, L. A. & Wesseley, S. (2003) Medically unexplained symptoms: exacerbating factors in the doctor–patient encounter. Journal of the Royal Society of Medicine, 96, 223–227. 6. Eriksen, T. E., Kerry, R., Mumford, S., Lie, S. A. N. & Anjum, R. L. (2013) At the borders of medical reasoning: aetiological and ontological challenges of medically unexplained symptoms. Philosophy, Ethics, and Humanities in Medicine, 8 (11), 1–11. 7. Knotternus, J. A. & Buntinx, F. (2008) The Evidence Base of Clinical Diagnosis. Oxford, UK: Wiley-Blackwell. 8. Josephson, J. R. & Josephson, S. G. (eds) (1994) Abductive Inference. Cambridge: Cambridge University Press. 9. Rodriguez de Romo, A., Aliseda, A. & Arauz, A. (2008) Medicine and Reasoning: The Diagnostic Process in Neurology. Ludas Vitalis. 10. Smith, R. & Francesca, D. (2007) Classification and diagnosis of patients with medically unexplained symptoms. Journal of General Internal Medicine, 22 (5), 685–691. 11. Spiegel, B., Farid, M., Esrailian, E., Talley, J. & Chang, L. (2010) Is irritable bowel syndrome a diagnosis of exclusion? A survey of primary care providers, gastroenterologists, and IBS experts. The American Journal of Gastroenterology, 105 (4), 848–858. 12. Kennedy, A. G. (2013) Differential diagnosis and the suspension of judgment. The Journal of Medicine and Philosophy, 38 (5), 487–500. 13. Illari, P. M. & Williamson, J. (2012) What is a mechanism? Thinking about mechanisms across the sciences. European Journal for Philosophy of Science, 2 (1), 119–135. 14. Van Ravenzwaaij, J., Olde Hartman, T. C., Van Ravesteijn, H., Eveleigh, R., Van Rijswijk, E. & Lucassen, P. L. B. J. (2010) Explanatory models of medically unexplained symptoms: a qualitative analysis of the literature. Mental Health in Family Medicine, 7, 223–231. 15. Machamer, P., Darden, L. & Craver, C. (2000) Thinking about mechanisms. Philosophy of Science, 67 (1), 1–25. 16. Turner, S. (2013) Where explanation ends: understanding as the place the spade turns in the social sciences. Studies in History and Philosophy of Science, 44, 532–538. 17. Gijsbers, V. (2013) Understanding, explanation, and unification. Studies in History and Philosophy of Science, 44, 516–522. 18. Strevens, M. (2013) No understanding without explanation. Studies in History and Philosophy of Science, 44, 510–515. 19. De Vreese, L., Weber, E. & Van Bouwel, J. (2010) Explanatory pluralism in the medical sciences: theory and practice. Theoretical Medicine and Bioethics, 31, 371–390.
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20. Van Fraassen, B. C. (1980) The Scientific Image. Oxford: Clarendon Press. 21. Kellert, S. H., Longino, H. E. & Waters, C. K. (2006) Introduction: the pluralist stance. In Scientific Pluralism (eds S. H. Kellert, H. E. Longino & C. K. Waters), pp. vii–xxix. Minneapolis: University of Minnesota Press. 22. Longino, H. (2006) Theoretical pluralism and the scientific study of behavior. In Scientific Pluralism (eds S. H. Kellert, H. E. Longino & C. K. Waters), pp. 102–131. Minneapolis: University of Minnesota Press. 23. Keller, E. F. (2002) Making Sense of Life: Explaining Biological Development with Models, Metaphors, and Machines. Cambridge: Harvard University Press.
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24. Fortun, M., Fortun, K., Costelloe-Kuehn, B., Saheb, T., Price, D., Kenner, A. & Crowder, J. (2014) Asthma, culture, and cultural analysis: continuing challenges. In Heterogeneity in Asthma (ed. A. R. Brasier), pp. 321–332. New York: Springer. 25. Brookes, T. (1994) Catching My Breath: An Asthmatic Explores His Illness. New York: Times Books. 26. Marcum, J. (2008) Reflections on humanizing biomedicine. Perspectives in Biology and Medicine, 51 (3), 392–405. 27. Butler, C. C., Evans, M., Greaves, D. & Simpson, S. (2004) Medically unexplained symptoms: the biopsychosocial model found wanting. Journal of the Royal Society of Medicine, 97, 219–222. 28. Freudenreich, O. (2012) Differential diagnosis of psychotic symptoms: medical mimics. Psychiatric Times, 3 December 2012.
© 2014 John Wiley & Sons, Ltd.
Journal of Evaluation in Clinical Practice ISSN 1365-2753
Causal explanatory pluralism and medically unexplained physical symptoms Michael Cournoyea BSc1 and Ashley Graham Kennedy PhD2 1
PhD Candidate, Institute for the History and Philosophy of Science and Technology, University of Toronto, Toronto, ON, Canada Assistant Professor of Philosophy, Wilkes Honors College, and Assistant Professor of Clinical Biomedical Science (secondary), Charles E. Schmidt College of Medicine, Florida Atlantic University, Jupiter, FL, USA
2
Keywords diagnosis, explanation, patient-centred care, person-centred medicine Correspondence Mr Michael Cournoyea Institute for the History and Philosophy of Science and Technology University of Toronto Toronto, Ontario M5S 1K7 Canada E-mail: [email protected]
Abstract In this paper, we propose a methodology for investigating medically unexplained physical symptoms (MUPSs). These symptoms are common in both primary and specialist medical practices, but are poorly understood. Currently, MUPSs are diagnosed via non-explanatory labels. However, we show that explanatory diagnoses are preferable to non-explanatory syndromic diagnoses because they bring both epistemic and therapeutic benefits to patients and their providers. Thus, we advocate a methodology of causal explanatory pluralism in the diagnostic workup and clinical management of MUPSs.
Accepted for publication: 29 July 2014 doi:10.1111/jep.12238
Introduction Medically unexplained physical symptoms (MUPSs1) are shockingly common in both primary and specialist practices; estimates of patients that present with MUPS range from 25% to 70%, with higher percentages among certain demographics and those that present to specialists [1,2]. These symptoms range from acute to chronic, mild to severe, and explanatorily probabilistic to impenetrably obscure. Some chronic collections of symptoms have been labelled as syndromes, such as irritable bowel syndrome, multiple chemical sensitivity, fibromyalgia, or chronic fatigue and immune dysfunction syndrome. Patients that exhibit these syndromes often 1
In the medical literature, MUPSs are sometimes referred to simply as MUS (medically unexplained symptom) or even ‘somatization’. We prefer the acronym MUPSS (medically unexplained physiological signs/ symptom), but have opted to use MUPS for consistency with the literature. We prefer to use ‘physiological’ rather than ‘physical’ because it denotes a more accurate class of signs/symptoms and we include ‘signs’ to acknowledge that signs can be unexplained. Medical signs such as hypertension are often taken to be objective facts, clearly explained; however, while it may be clear what a sign is, it is not always clear why a sign is present. In addition, ‘MUPS’ is used interchangeably (and sometimes ambiguously) to refer to a category of illnesses, illnesses themselves (IBS, CFIDS, etc.), or single signs/symptoms that remain unexplained (lower back pain, fever, etc.).
Journal of Evaluation in Clinical Practice (2014) © 2014 John Wiley & Sons, Ltd.
move continuously between medical specialists and receive a variety of uncertain diagnoses [3–5]. The medical literature on MUPS is overwhelming, but from a philosophical perspective, little has been written on the topic, leaving open the questions of how MUPSs are (and should be) explained and how and why medical ontologists exclude MUPS.2 Since MUPS refers to several syndromes, one strategy might be to address each syndrome separately rather than attempting to find a unified account of MUPS. In contrast, we aim to address the methodological question of how MUPS should be explained in general, proposing that MUPS diagnoses should be approached pluralistically.
The diagnostic ideal It is uncontroversial in the medical literature that the ideal diagnosis is a biomedical causal explanation [7,8].3 This is generally arrived at via a process of observation, testing and an often complex combination of deductive, inductive and abductive 2
See Eriksen et al. [6] for a discussion of how dispositional ontologies may better accommodate MUPS. 3 This is not to say that this is the only type of diagnosis. As we will discuss in a later section, some diagnoses are syndromic diagnoses and do not posit causes. However, the ideal diagnosis in current medical practice is a causal explanation – whether topologic or (preferably) aetiologic.
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reasoning [9]. Such a diagnosis posits a physiological cause for a set of physical signs and symptoms.4 A physical sign is something that can be observed directly by the doctor via testing and/or physical examination; a physical symptom is a patient reported discomfort or abnormality. For example, the diagnosis of strep throat, a bacterial infection caused by Streptococcus pyogenes, is a biomedical causal diagnosis that makes use of both physical signs (e.g. a positive Strep culture) and symptoms (e.g. a painfully sore throat). Thus, in the case of a sore throat coupled with a positive strep culture, a strep infection is said to be the physiological cause of the physical signs and symptoms. Knowing this physiological cause allows the clinician to target and treat the causal process; in turn, this will hopefully lead to the resolution of the patient’s discomfort. Treating patients by intervening on physiological causes is the primary goal of biomedicine as currently practised. For example, penicillin is the first-line treatment for strep throat, which, when administered in the correct dosage for the appropriate length of time, does in fact lead to a full resolution of the signs and symptoms in the vast majority of patients because it targets the physiological cause of the illness. Of course, not all known physiological causes of physical signs and symptoms have available medical treatments. This is not a concern we will address here. Instead, we are interested in how contemporary medicine attempts to explain physical signs and symptoms with an unknown physiological cause. While strep throat is an uncontroversial example of a biomedical causal diagnosis (with a readily available and effective medical treatment), many diagnoses fall short of this ideal. In the most challenging cases, patients receive ‘syndromic diagnoses’ that lack a causal explanation, as is the case with MUPS where explanatory diagnoses are not available. Syndromic diagnoses are agnostic concerning underlying aetiological or structural explanations. This not only means that the cause of these signs and symptoms is unknown, it also usually means that it is not known how to treat the disorder in question.
Diagnosis by exclusion Most diagnoses of unknown cause are arrived at via the process of diagnosis by exclusion [10,11]. Diagnosis by exclusion proceeds as a part of the process of differential diagnosis, where a doctor will come up with a list (or ‘differential’) of probable diagnoses. The doctor decides what to put in a differential by looking at pieces of positive evidence (or evidence for certain conditions). Then, when deciding what to exclude from a differential, a doctor might consider alternatives using negative evidence (or evidence against certain conditions). To see how this process works, consider the following case study as an example:5 Brad is a 43-year-old motivational speaker and married father of four young children who was entirely well until six months ago. Brad now presents with the chief complaints of persistent fatigue, recurrent flu-like symptoms and difficulty concentrating. He says that whenever he ‘pushes’ himself, he experiences terrible exhaustion, muscle pain, aching in various joints, soreness in the neck, and burning eyes. These 4
There can of course be more than one physiological cause. The italicized portion of this section was adapted from the ‘Case Studies’ section of http://www.cfids.org. 5
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symptoms may last one or two days, then subside somewhat. He has become clumsy and bumps into things around the house. He notes new difficulties with memory, simple decisions, basic calculations, and word searching. He has noticed increasing mental confusion, distractibility and disorientation in familiar surroundings. His complaints include generalized weakness, ‘restless’ legs and jerking at night, night sweats, tender glands in the neck and a feverish feeling despite subnormal body temperatures. His sleep is shallow and disrupted, and he wakes up feeling worse than when he went to bed. Brad awoke one morning with fever and a ‘terrible flulike feeling.’ He consulted his primary physician when he did not improve over several days. Initial evaluation revealed mildly elevated liver function and a slightly positive antinuclear antibody (ANA) test, but otherwise the examination and laboratory testing did not reveal the cause of his illness. He has been essentially housebound for the past six months, but is able to handle most of his personal activities of daily living. He has been physically active for up to four hours at a time ‘safely’, but some days he has been unable to do anything. Brad’s past medical history is remarkable only for herniorrhaphy, and repair of a severed nerve. There is no history of hair loss, sun sensitivity, recurrent rash, recurrent mouth ulcers, Raynaud’s phenomenon, or kidney disease. There has been no swelling, heat, or redness at the joints. There has been no abdominal pain or recurrent diarrhea of note. Brad reports a travel history, recalling a backwoods camping trip in Wisconsin with the family sometime prior to the onset of his symptoms. Given this history and set of symptoms, Brad’s physician might reasonably come up with the following differential: 1 A collagen vascular disorder such as lupus. 2 A rheumatological disorder such as rheumatoid arthritis (RA). 3 An infectious disease such as Lyme disease or a virus. 4 Chronic fatigue and immune dysfunction syndrome (CFIDS). Let us suppose that a repeat ANA is negative, making the diagnosis of lupus unlikely. Similarly, a workup for RA is unremarkable. If this is the case, the doctor might then test for some infectious causes of Brad’s illness such as cytomegalovirus, Epstein–Barr virus or Lyme disease.6 Supposing that these laboratory studies are also negative, the results together constitute negative evidence for the diagnosis (by exclusion) of CFIDS. In other words, if the other diagnoses in the differential are ruled out, then a diagnosis of CFIDS will likely be made, if positive evidence for the syndrome is also present. To meet the case definition criteria for the positive evidence for CFIDS, a patient must have had persistent or relapsing fatigue for more than 6 months with no pre-existing illness to explain the debilitating fatigue. In addition, the patient must have at least four of eight symptom criteria: (1) cognitive symptoms; (2) sore throat; (3) tender cervical/axillary lymph nodes; (4) myalgias; (5) arthralgias; (6) headache (of a new type or severity); (7) unrefreshing sleep; or (8) post-exertional malaise. 6
Clearly, it is not possible to rule out all infectious agents in this case, or others like it (there are more than 60 infectious conditions that share symptoms with CFIDS). Generally, no attempt is made to do so. Instead, the doctor tests for certain likely illnesses (where likelihood is determined by the doctor) and if these tests turn out to be negative the category of ‘infectious agent’ is eliminated from the differential.
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If a patient, like Brad, meets four of these criteria and has negative laboratory results, he or she will very likely be diagnosed with CFIDS.7 However, this diagnosis, and the method by which it is obtained, is problematic for at least two reasons. Firstly, because it is never feasible to rule out all possible alternative diagnoses, any diagnosis arrived at via the process of differential diagnosis is inherently uncertain. Secondly, and more problematically, when a causal explanation for a set of signs and symptoms is not described as part of the diagnostic process, as in the case of a syndromic diagnosis, the diagnosis lacks the epistemic and therapeutic benefits that are conferred with an explanation (which we discuss in the section The benefits of an explanatory diagnosis). Syndromic diagnoses of MUPS are lacking for these reasons. If causal physiological diagnosis is the gold standard in contemporary medicine, then why are syndromic diagnoses ever made? The most common reason for a syndromic diagnosis is pragmatic: once a diagnosis has been made, a doctor will then stop investigation into the cause of the patient’s illness. This means that time and money will not be spent on further investigation into the cause of the patient’s illness, even though the illness remains underdetermined.8 However, the pragmatic gain in such instances is often outweighed by epistemic and therapeutic losses. In what follows, we argue that causal diagnoses are preferable to syndromic diagnoses for both epistemic and therapeutic reasons.9 Because of this, we argue that causal explanatory diagnoses should be pursued in MUPS via a methodology of explanatory pluralism, even when biomedical causal mechanistic diagnoses, specifically, may not be available. 7
Or diagnosed with a psychosomatic disorder. One problematic use of diagnosis by exclusion occurs when a doctor concludes that a patient has a psychiatric illness when ‘he or she is unable to find anything that would normally be expected in a workup for somatic diseases, x, y, z, etc.’ [12, p. 7]. Of course, psychiatric diagnoses should not be made based on negative evidence alone: ‘The proper diagnosis of both physical and psychiatric illnesses requires the presence of clearly defined signs and symptoms consistent with the diagnostic category’ [12, p. 7]. Unfortunately, many MUPSs are misdiagnosed as psychiatric illnesses. 8 Clinical underdetermination occurs when no justifiable choice can be made between two or more rival diagnoses in a differential, given the available evidence. We might suspect that Brad has a viral infection, for example, and outline a differential of several viral candidates; before we perform viral-specific tests; however, the available evidence is insufficient to justify a viral-specific diagnosis. Since we cannot causally explain Brad’s illness at this stage, we cannot give Brad a causally specific diagnosis. This is always the case with MUPS. If no available tests can causally explain Brad’s illness, then he is given a syndromic diagnosis (such as CFIDS) that is, by definition, underdetermined. Consider an analogy. If an optical anomaly is discovered on a deep space telescope, we might not know whether the anomaly is a new star, a mechanical glitch, or an uncanny smudge on the telescope’s lens. Without further evidence, any belief we might have about the anomaly’s true cause is underdetermined by the available evidence. We might even give the anomaly a provisional label and apply this provisional label to similar anomalies. As with MUPS, simply labelling the anomaly is a diagnostic last resort. 9 The pursuit of causal mechanistic explanatory diagnoses is always preferable to settling for syndromic diagnoses, especially when such explanatory diagnoses offer plausible accounts for a condition. This does not imply that every explanatory diagnosis will be better than a syndromic diagnosis, since explanatory diagnoses may be false and potentially harmful. Solid clinical judgement is essential to deciding whether explanatory diagnoses may produce more epistemic and therapeutic harm than an alternative. Thanks to an anonymous reviewer for this clarification.
© 2014 John Wiley & Sons, Ltd.
Causal explanatory pluralism and MUPS
Causal explanations in biomedicine Causal diagnoses in biomedicine aim to explain physical signs and symptoms in terms of either structural causes or pathophysiological mechanisms. These two types of causal diagnoses are not mutually exclusive. For example, blurred vision and headache might be explained causally in terms of a (structural) brain lesion, which, in turn, might be caused by a (mechanistic) cancerous process. A mechanistic explanation is nearly always more fundamental than a topological or structural one and as such is considered the gold standard of medical diagnoses.10 In the case of MUPS, by definition, no causal explanatory mechanism has been identified for the disorder in question. This does not mean that causal explanatory strategies are not being employed to address MUPS. For instance, Van Ravenzwaaij et al. [14] described nine explanatory models for MUPS, each offering a unique causal mechanistic theory. In their review, they described models from 19 articles drawn from the PubMed and PsycINFO databases (between 2005 and 2010). In this list, there are physical explanations (immune system sensitization theory, endocrine dysregulation theory, autonomic nervous system dysfunction theory and abnormal proprioception theory), psychological explanations (somatosensory amplification theory, sensitivity theory) and hybrid explanations (sensitization theory, signal filter theory and an illness behaviour model). These models remain quite theoretical and Van Ravenzwaaij et al. do not suggest that they apply to particular MUPS or to MUPS more broadly. The strength of these models is in offering causal mechanisms that may help to answer context-specific questions (as outlined in the section An argument for explanatory pluralism). As such, they have the potential to bring epistemic and therapeutic benefits to patients and providers that syndromic diagnoses cannot and do not bring.
The benefits of an explanatory diagnosis As we have seen, MUPSs are non-explanatory, syndromic diagnoses that serve only as optimistic placeholders for future causal explanations. While syndromic diagnoses do not confer the full epistemic and therapeutic benefits of explanatory diagnoses, they can give patients hope concerning their conditions [1]. Explanatory diagnoses, on the contrary, provide understanding to both patients and clinicians. They can do this even in cases in which they are incomplete or only partially correct. According to Machamer et al. [15, p. 21]: The understanding provided by a mechanistic explanation may be correct or incorrect. Either way, the explanation renders a phenomenon intelligible. Intelligibility arises not from an explanation’s correctness, but rather from an elucidative relation between the explanans (the set-up conditions and intermediate entities and activities) and the explanandum (the termination condition or the phenomenon to be explained).
10 We adopt the widely applicable account of mechanisms outlined by Illari and Williamson: ‘A mechanism for a phenomenon consists of entities and activities organized in such a way that they are responsible for the phenomenon’ [13, p. 130].
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Thus, even partially explanatory diagnoses can confer benefit by making the disease intelligible to the patient and the provider, and by allowing clinicians to develop treatments and outline prognoses. In other words, causal mechanistic diagnoses are sought because pathophysiological mechanisms render diagnoses more satisfying, convincing and fruitful [16].11 While Gijsbers [17] argued that non-explanatory, classificatory theories can lead to intelligibility, we doubt that this is the case with syndromic classifications. While syndromic diagnoses help to build patient communities, fuel advocacy and encourage research, they do not unify illnesses intelligibly. Syndromic diagnoses are useful only as temporary placeholders. Explanatory diagnoses, on the contrary, answer the question of why (physiologically) a patient has a disease by connecting the patient’s signs and symptoms to the disease. Prior to an explanatory diagnosis, the patient is already keenly aware of his signs and symptoms, but he does not understand why or how they connect to an aetiology. According to Strevens, to understand why is to have an ‘intimate acquaintance with the structure of the explanation’ [18, p. 5] such that signs and symptoms are structured into an aetiology; this is exactly what is missing in non-explanatory, syndromic diagnoses. In cases of MUPS, patients may understand that they have a certain set of signs and symptoms, but they (and their clinicians) do not understand why they have them.12 Because of this, they cannot glean the full epistemic and therapeutic benefits that are available from explanatory diagnoses. These benefits are separate from the therapeutic benefits of any medical treatment developed from such a diagnostic explanation. In other words, the understanding derived from an explanatory diagnosis is therapeutic to patients in its own right. Patients that understand why they have certain symptoms get better faster than patients who do not. Van Ravenzwaaij et al. [14, p. 229] highlight this in their qualitative literature review, writing that: Plenty of doctors think in terms of action and reaction, while the explanation of symptoms in itself might be the most important intervention for patients with MUPS. Kirmayer et al. [1] also noted the importance of meaning-making and narrating distress in their intensive interviews of 18 CanadianVietnamese immigrants who presented with MUPS. In their ethnographic interviews, participants felt some alleviation when they ‘were able to provide a meaning for their symptoms – whether by referring to a biomedical diagnosis, folk label, or explanatory model’ [1, p. 667]. Those that could not explain their conditions using a biomedical or cultural model felt ‘misled and let down’ in a ‘semantic no man’s land outside social consensus and collective meaning’ [1, p. 667]. That an explanation can be a therapeutic tool speaks to the virtue of understanding in the medical encounter and the importance of pursing correct explanatory diagnoses. If understanding is both an epistemic virtue and a therapeutic tool, then it becomes evident why MUPSs are deeply unsettling to patients and clinicians alike. 11
We should emphasize that causal mechanistic explanations bestow such benefits, but these explanations need not be reductionistic; we leave a discussion of non-mechanistic explanations to future work. 12 We do not wish to make the claim that any answer to a ‘why’ question is a good one. Certainly, accurate diagnoses are preferable to inaccurate ones. However, as we have already noted, even incomplete or partial explanations can bring benefits that mere labels cannot.
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An argument for explanatory pluralism We have seen that explanatory diagnoses can confer epistemic and therapeutic benefits both to patients suffering from MUPS and to their health care providers. In this section, we will argue that explanatory pluralism is the most appropriate explanatory methodology for addressing MUPS in the clinic. We advocate a version of pluralism outlined by De Vreese et al. [19], a non-integrative methodological explanatory pluralism that privileges neither reductionism nor holism: [. . .] methodological explanatory pluralism consists in the claim that the best form and level of explanation depends on the kind of question one seeks to answer by the explanation [19, p. 374]. De Vreese et al. [19] conceived explanatory levels as incommensurable and non-supervening layers of a complete explanation (e.g. physiological and socio-economic explanations for obesity). The aim of explanatory pluralism is to find explanations that provide the most adequate, efficient and accurate information, given the explanatory questions and context. Although De Vreese et al. [19] conceived this methodology as beneficial in the research setting, we think that its benefits also extend to the clinical diagnostic management of MUPS. Non-integrative explanatory pluralism does not attempt to (1) integrate pluralistic explanations (to avoid cumbersome explanations); (2) make metaphysical claims about pluralism (as a theory of explanation); nor (3) privilege one explanatory strategy over another (i.e. it is pluralistic). This form of explanatory pluralism does not imply that any explanation goes, nor that we need to be anti-realists about MUPS. If we ask ‘Why does Brad have CFIDS?’, we need to be more specific about the aims of such a question, and ultimately we may not come to one unificatory explanation of Brad’s CFIDS, even though we may be able to answer some of the why questions concerning his situation. Consider the three questions that De Vreese et al. [19] outlined using Brad’s CFIDS: ‘Why did Brad develop CFIDS?’ can be separated into: 1 Why did Brad, who has characteristic A, develop CFIDS, while Jamie, with characteristic A′, did not? 2 Why did Brad with behaviour B develop CFIDS, while Casey with behaviour B′ did not? 3 Why did Brad living in country C develop CFIDS, while Dylan in country C′ did not? The three questions are elaborations and specifications based upon Van Fraasen’s [20] erotetic model of explanation (i.e. a theory of why-questions). Each question addresses a different relevant context: (1) micro-reductive; (2) micro-non-reductive; and (3) macro-holistic [19]. De Vreese et al. [19] emphasized that each question has the potential to yield an adequate, efficient and accurate answer without reducing the other questions. We may be able to answer (1) without (2) or (3), for example, and in doing so provide a partial explanation for Brad’s CFIDS. The explanatory models proposed by Van Ravenzwaaij et al. [14] may help to answer some of these questions. For example, endocrine dysregulation might offer a micro-reductive causal explanation for Brad’s CFIDS (as compared to Jamie’s CFIDS) that is adequate, efficient and accurate, even though it does not necessarily explain CFIDS more broadly. Treatment that intervenes on the hypothalamus–pituitary– adrenal (HPA) axis might be effective for Brad, though not Jamie, even if it does not completely alleviate Brad’s CFIDS.
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Answers to these questions allow us to understand why Brad developed CFIDS in these specific explanatory contexts. As Kellert et al. [21, p. xiv] noted in their description of the pluralistic stance, inquiry ‘typically represents some aspects of the world at the cost of obscuring, or perhaps distorting, other aspects.’ Helen Longino [22] likewise advocated for pluralism in explanations of behaviour, where different approaches yield partial knowledges that compose ‘a nonunifiable plurality’ (p. 111). Explanatory pluralism is not merely a pragmatic compromise when complex cases defy explanation; such pluralism allows us to understand why more adequately, efficiently and accurately in each relevant context with the ultimate aim of discovering causal explanations. This approach does not offer a single, clear aetiology, but it does aim for a causal explanation. In practice, this approach encourages doctors to focus on specific ‘why’ questions and their answers, rather than resorting to syndromic diagnoses. Even medically explained diseases can benefit from a culture of explanatory pluralism [23]. Fortun et al. [24] recommended explanatory pluralism in tackling the ‘complex dynamics’ of asthma, as ‘modern biomedical culture expects pluralities to be reduced, “mysteries” to be cleared up, with straightforward and preferably singular explanations, after sufficient rational effort has been expended’ (p. 330). They highlight Tim Brookes’ [25] autobiographical account of asthma as he searched for the cause of his illness, feeling that ‘this was what was needed to care for, if not cure, himself’ [25, p. 326]. However, finding the cause of an illness is not always possible, nor is it strictly necessary, even from a treatment perspective. In some cases, finding a cause can be enough – from both an epistemic and a therapeutic standpoint. Engel’s biopsychosocial model may seem helpful for integrating the layered factors in our proposed pluralism. Engel’s goal was to ‘re-humanize’ biomedicine by considering the psychological and social factors essential to illness [26]. Yet Engel’s proposal leads to cumbersome triple diagnoses. Butler et al. [27] argued that the problem with Engel’s model, specifically when addressing MUPS, has historical precedent in ‘the analytic philosophical tradition to break down complex phenomena in the hope of finding meaning in the simpler constituents (reductionism)’ [27, p. 219]. They advocate an ‘interpretive approach’ that engages with patients’ experiences as ‘phenomena to be interpreted’ [27, p. 220]. We will not reiterate the many challenges to Engel’s model here (i.e. difficulties separating these components and integrating them distinctly) but it is important to note that Engel’s attempt at methodological pluralism points to the problem (i.e. reductionist biomedicine) but not to a satisfactory solution. Our solution to this problem is to suggest a methodological approach of explanatory pluralism in the diagnostic workup of MUPS. This methodology also encourages clinicians to refrain from making unjustified psychiatric diagnoses in cases of MUPS. While ‘the number of medical diseases that can present with psychotic symptoms is legion’ [28], it is of course important in any diagnostic workup to differentiate between primary and secondary psychiatric symptoms. This is especially important in cases of MUPS: if psychiatric ‘diagnoses’ are too quickly given in these cases, it causes premature closure into causal investigations, thereby reducing the chance of arriving at an accurate causal diagnosis. While we do not wish to argue that psychiatric diagnoses are never appropriate in cases of MUPS, it is important for clinicians to
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Causal explanatory pluralism and MUPS
remember that they should be made only when the presenting evidence is sufficient. In summary, as we have seen, causal diagnoses carry therapeutic and epistemic benefits for both patients and clinicians – even when they do not lead directly to the treatment for the conditions they describe. Because of this, they ought to be pursued in MUPS.
References 1. Kirmayer, L. J., Groleau, D., Looper, K. J. & Dominicé, M. (2004) Explaining medically unexplained symptoms. Canadian Journal of Psychiatry, 49 (10), 663–672. 2. Reid, S., Wessely, S., Crayford, T. & Hotopf, M. (2001) Medically unexplained symptoms in frequent attenders of secondary health care: retrospective cohort study. British Medical Journal, 322, 1–4. 3. Atkins, C. G. K., Brownell, K., Kornelsen, J., Woollard, R. & Whiteley, A. (2013) Silos of silence, stress, and suffering: patient and physician experiences of MUPS and diagnostic uncertainty. AJOB Neuroscience, 4 (3), 3–8. 4. O’Rourke, M. (2013) What’s wrong with me? The New Yorker, 26 August 2013. Available at: http://www.newyorker.com/magazine/ 2013/08/26/whats-wrong-with-me (last accessed 22 February 2014). 5. Page, L. A. & Wesseley, S. (2003) Medically unexplained symptoms: exacerbating factors in the doctor–patient encounter. Journal of the Royal Society of Medicine, 96, 223–227. 6. Eriksen, T. E., Kerry, R., Mumford, S., Lie, S. A. N. & Anjum, R. L. (2013) At the borders of medical reasoning: aetiological and ontological challenges of medically unexplained symptoms. Philosophy, Ethics, and Humanities in Medicine, 8 (11), 1–11. 7. Knotternus, J. A. & Buntinx, F. (2008) The Evidence Base of Clinical Diagnosis. Oxford, UK: Wiley-Blackwell. 8. Josephson, J. R. & Josephson, S. G. (eds) (1994) Abductive Inference. Cambridge: Cambridge University Press. 9. Rodriguez de Romo, A., Aliseda, A. & Arauz, A. (2008) Medicine and Reasoning: The Diagnostic Process in Neurology. Ludas Vitalis. 10. Smith, R. & Francesca, D. (2007) Classification and diagnosis of patients with medically unexplained symptoms. Journal of General Internal Medicine, 22 (5), 685–691. 11. Spiegel, B., Farid, M., Esrailian, E., Talley, J. & Chang, L. (2010) Is irritable bowel syndrome a diagnosis of exclusion? A survey of primary care providers, gastroenterologists, and IBS experts. The American Journal of Gastroenterology, 105 (4), 848–858. 12. Kennedy, A. G. (2013) Differential diagnosis and the suspension of judgment. The Journal of Medicine and Philosophy, 38 (5), 487–500. 13. Illari, P. M. & Williamson, J. (2012) What is a mechanism? Thinking about mechanisms across the sciences. European Journal for Philosophy of Science, 2 (1), 119–135. 14. Van Ravenzwaaij, J., Olde Hartman, T. C., Van Ravesteijn, H., Eveleigh, R., Van Rijswijk, E. & Lucassen, P. L. B. J. (2010) Explanatory models of medically unexplained symptoms: a qualitative analysis of the literature. Mental Health in Family Medicine, 7, 223–231. 15. Machamer, P., Darden, L. & Craver, C. (2000) Thinking about mechanisms. Philosophy of Science, 67 (1), 1–25. 16. Turner, S. (2013) Where explanation ends: understanding as the place the spade turns in the social sciences. Studies in History and Philosophy of Science, 44, 532–538. 17. Gijsbers, V. (2013) Understanding, explanation, and unification. Studies in History and Philosophy of Science, 44, 516–522. 18. Strevens, M. (2013) No understanding without explanation. Studies in History and Philosophy of Science, 44, 510–515. 19. De Vreese, L., Weber, E. & Van Bouwel, J. (2010) Explanatory pluralism in the medical sciences: theory and practice. Theoretical Medicine and Bioethics, 31, 371–390.
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20. Van Fraassen, B. C. (1980) The Scientific Image. Oxford: Clarendon Press. 21. Kellert, S. H., Longino, H. E. & Waters, C. K. (2006) Introduction: the pluralist stance. In Scientific Pluralism (eds S. H. Kellert, H. E. Longino & C. K. Waters), pp. vii–xxix. Minneapolis: University of Minnesota Press. 22. Longino, H. (2006) Theoretical pluralism and the scientific study of behavior. In Scientific Pluralism (eds S. H. Kellert, H. E. Longino & C. K. Waters), pp. 102–131. Minneapolis: University of Minnesota Press. 23. Keller, E. F. (2002) Making Sense of Life: Explaining Biological Development with Models, Metaphors, and Machines. Cambridge: Harvard University Press.
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24. Fortun, M., Fortun, K., Costelloe-Kuehn, B., Saheb, T., Price, D., Kenner, A. & Crowder, J. (2014) Asthma, culture, and cultural analysis: continuing challenges. In Heterogeneity in Asthma (ed. A. R. Brasier), pp. 321–332. New York: Springer. 25. Brookes, T. (1994) Catching My Breath: An Asthmatic Explores His Illness. New York: Times Books. 26. Marcum, J. (2008) Reflections on humanizing biomedicine. Perspectives in Biology and Medicine, 51 (3), 392–405. 27. Butler, C. C., Evans, M., Greaves, D. & Simpson, S. (2004) Medically unexplained symptoms: the biopsychosocial model found wanting. Journal of the Royal Society of Medicine, 97, 219–222. 28. Freudenreich, O. (2012) Differential diagnosis of psychotic symptoms: medical mimics. Psychiatric Times, 3 December 2012.
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