The causal explanatory functions of medical diagnoses

Abstract

Diagnoses in medicine are often taken to serve as explanations of patients’ symptoms and signs. This article examines how they do so. I begin by arguing that although some instances of diagnostic explanation can be formulated as covering law arguments, they are explanatory neither in virtue of their argumentative structures nor in virtue of general regularities between diagnoses and clinical presentations. I then consider the theory that medical diagnoses explain symptoms and signs by identifying their actual causes in particular cases. While I take this to be largely correct, I argue that for a diagnosis to function as a satisfactory causal explanation of a patient’s symptoms and signs, it also needs to be supplemented by understanding the mechanisms by which the identified cause produces the symptoms and signs. This mechanistic understanding comes not from the diagnosis itself, but rather from the theoretical framework within which the physician operates.

The Theory of Evidence-Based Practice: A Reformulation of the Evidence-Based Practice Inquiry Model

“…(Maung, 2017, p. 52), supports the claim that the diagnosed condition (lung carcinoma) can cause the presenting symptoms (muscle weakness, fragile skin, abdominal obesity). Maung (2017) further notes that providing mechanistic explanations of pathology supports the therapeutic aims of medicine. In understanding the mechanisms at play, physicians/clinicians are able to isolate certain targets in the causal chain, and potentially intervene for therapeutic reasons.…”

“…Each of these forms of reasoning rely on understandings of basic scientific processes in humans and attempt to explain underlying mechanisms of change (Solomon, 2015). Having knowledge of mechanisms provides a richer understanding of causal processes and can be useful for increasing effectiveness in therapy (Maung, 2017), but at the same time, mechanisms are more difficult to evaluate objectively (Russo & Williamson, 2011). A great deal of philosophy of science literature delves into discussions around causality and mechanisms in biology (see, Maung, 2017;Russo & Williamson, 2007Ross, 2018;Thomas & Sharp, 2019), with this research providing clear instances of the value of mechanistic reasoning.…”

“…Using an example from the medical literature, Maung (2017) demonstrates how the understanding of mechanisms can allow diagnosis to function as a sufficient explanation of a patient's presenting problems and can subsequently maximise therapeutic effectiveness. Consider the case of an individual who presents with a recent onset of muscle weakness, abdominal obesity, and fragile skin, and is diagnosed with lung carcinoma.…”

“…In this thesis, I have explored several of the major criticisms of EBP, discussing their legitimacy through a theoretical lens. Such criticisms include the use of an evidence hierarchy (Bluhm, 2005;Borgerson, 2009;Upshur, 2005;Stegenga, 2014Stegenga, , 2018, limited conceptions of evidence (Solomon, 2015;Stegenga, 2018;Maung, 2017), under acknowledgement of values (Ward & Heffernan, 2017;Ward & McDonald, in press), issues with external validity (Kazdin, 2008;Kvernbekk, 2011;Solomon, 2015;Westen et al, 2004), devaluing of clinical expertise (Tonelli, 2019), stifling of research creativity (Bohart, 2000), overlooking problems with limited research knowledge (Solomon, 2015), and lack of attention to cultural values and norms (Washington, 2016). Examining these critiques through a theoretical lens uncovered several underlying issues with EBP model that make it difficult to implement into clinical psychology practice.…”

“…Although these revisions go some way to addressing the theoretical and conceptual issues associated with the inquiry model, further research into the practice of EBP will be fruitful for the field. Just as research in the biological sciences has examined the concepts of mechanisms and causality (Maung, 2017;Russo & Williamson, 2007Ross, 2018;Thomas & Sharp, 2019), so would clinical psychology research benefit greatly from a greater concentration on the development of mechanistic explanations for psychological problems. Although it has been noted that mechanistic explanations are harder to evaluate objectively compared to empirical research findings (Russo & Williamson, 2011), it should not deter the field from attempting to understand mechanistic causal claims in psychological science.…”