Tuesday, 23 February 2016

Are Mental Disorders Natural Kinds?

This post is by Şerife Tekin (pictured above), Assistant Professor of Philosophy at Daemen College. Here she summarises her paper ‘Are Mental Disorders Natural Kinds? A Plea for a New Approach to Intervention in Psychiatry’, forthcoming in Philosophy, Psychiatry, and Psychology.

Thanks to Ema for inviting me to share my work with the Imperfect Cognitions blog readers. What follows is a snapshot of my arguments in the paper mentioned above. In the article I engage a debate with a long history in philosophy of science: the metaphysical status of mental disorders and empirical investigatibility. I offer an evaluation of what I call a Looping Debate (Tekin 2014), and recommend its replacement with a Trilateral Strategy.

Among philosophers interested in metaphysical and epistemological issues of psychiatric classification, the application of the theory of natural kinds to mental disorder is a particularly contentious topic (e.g. Hacking 1995; Cooper 2004, Zachar 2000; Graham 2010; Kendler, Zachar, and Craver 2010; Samuels 2009). For many, the concept of natural kind is appealing because of its conceived utility in scientific generalizations. Members of a particular natural kind are thought to share a large number of scientifically relevant properties that ground scientific explanations, predictions, and interventions. If mental disorders are natural kinds, as many argue, the discovery of their shared properties can yield explanations, predictions, and interventions (Cooper 2007; Samuels 2009).

In short, the motivation to attribute natural kind status to mental disorders originates from the desire to make them amenable to manipulation. If the scientifically relevant properties of, say, bipolar disorder, can be identified in this fashion, we can formulate scientific explanations, offer predictions about their course, and develop interventions.

To date, the scientific legitimacy of mental disorders has largely hinged on their status as natural kinds. Many philosophers hotly contest this understanding, however, and have instigated a Looping Debate with proponents of the theory. They inquire into the scientifically relevant properties that will facilitate explanations, predictions, and interventions in psychiatry by adopting a comparative strategy. They evaluate whether mental disorders, such as schizophrenia, are 'fundamentally like or unlike kinds such as chemical elements, fundamental particles and biological species' (Cooper 2004: 76), and compare mental disorders to the paradigm examples of the natural kinds studied by other sciences to draw inferences about their empirical investigability (Hacking 1986, 1995; Cooper 2004; 2007; Bogen 1988; Douglas 1986; Samuels 2009; Zachar 2000).

On the one hand, proponents of the Looping Argument (LA) argue that mental disorders are not natural kinds because members of psychiatric kinds change in response to their scientific labels; natural kinds, they say, are not subject to such looping effects (Hacking 1986, 1995). As they are subject to looping effects, the properties of psychiatric kinds are inherently unstable and thereby unfit for developing successful explanations, reliable predictions, or effective interventions in psychiatry. Proponents of the Parity Argument (PA), on the other hand, point out that some clearly natural kinds are also subject to looping effects, and this is not an obstacle for their scientific investigation (Cooper 2004, 2007; Khalidi 2010). By the same token, having unstable properties should not rule out psychiatric (natural) kinds as legitimate targets of scientific inquiry.

Both parties in the debate use a comparative strategy, arguing for or against the status of mental disorders as natural kinds; both juxtapose mental disorders to paradigm examples of natural kinds, such as chemical elements or biological species.

An LA proponent, Ian Hacking, uses paradigmatic examples of natural kinds to argue against the claim that some human kinds, i.e., the phenomena related to human beings, their actions, sentiments, and mental disorders, are natural kinds. He compares human kinds, including mental disorders, with examples of what he takes to be natural kinds, such as mud and thyrotropin-releasing hormones. Meanwhile, Rachel Cooper, a proponent of the PA, compares mental disorders to biological species to defend the thesis that mental disorders are natural kinds.

My target of criticism is the presupposition that the comparative strategy employed by participants in the Looping Debate will yield a set of properties that will achieve three tasks in psychiatry: explanation, prediction, and intervention. I disagree with this understanding. As I see it, the Looping Debate focuses too much on the properties of paradigmatic natural kinds, such as chemical elements and biological species, and not enough on the properties of mental disorders.

I propose to replace the comparative strategy with what I call a Trilateral Strategy—a strategy guided by first-person accounts of individuals with mental disorders and the relevant clinical and scientific work on psychopathology. A triple-pronged examination, I argue, can take us to the properties instrumental for developing effective interventions in mental disorders – without having to settle their natural kind status. I remain neutral on whether the comparative strategy is useful for arriving at properties relevant for explanation and prediction. My argument is that those properties relevant to intervention are bona fide scientific properties. I illustrate these by using schizophrenia as an example.

I believe the philosophical examination of practical and urgent problems such as the empirical investigation of mental disorder is empty without actively learning from and engaging with the sciences that study it, as well as with those actually experiencing it. I am not alone in this view. My paper will contribute to a burgeoning body of work in philosophy of psychiatry that puts scientific research on mental disorders and patient testimonies at the centre of philosophical analysis.

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