Conceptual understanding of psychiatric diagnosis

As I said in my last post, a paper that has been influencing the Future Strategic DSM Committee has been Hyman (2021). The abstract concludes that "scientific results demonstrate that psychiatric disorders cannot reasonably be understood as discrete categories—and certainly not as natural kinds".

Hyman reaches conclusions with strong implications for current psychiatric diagnostic systems, such as DSM. For example, he states that "The currently predominant categorical nosologies are fundamentally in error and are damaging to science". He sees psychiatric and neurological disorders as "groupings of disorders that exhibit some internal scientific and clinical coherence, but also have changing and permeable boundaries that are negotiated by interested professional groups". His argument is primarily against seeing any distinctions between disorders and non-disorders and between disorders as categorical in nature. To summarise in another quote:-

If by natural kinds we mean categories of things existing in nature that are well bounded and have stable, cohesive causal structures, as is the case for chemical elements, then the poorly bounded, etiologically and pathophysiologically complex psychiatric disorders are something else entirely. 

For me, Hyman, and the Future Strategic DSM Committee in general, could go further in their conceptual understanding of psychiatric diagnosis. They still seem to be too enamoured of the possibilities for "localising the mind" in the brain. Despite the lack of evidence for biomedical markers of mental illness, psychiatry remains paradigmatically committed to the idea that mental functions must be localised in the brain in some way (see eg. previous post). Of course the brain is the vehicle for meaningful experiences, such as functional mental illness. But the brain does not create meaning; it is people as a whole that do that. 

In particular, a new DSM needs to re-create the distinction between functional and organic psychosis, which was present in DSM-I, and was abolished by DSM-IV (see previous post). I am not arguing for Cartesian dualism, splitting the mind from the brain (see eg. another previous post). Mind and body are integrated in the organism. People are animate, embodied beings. But what needs to be made clear is that naturalistic explanations of primary mental illness are inadequate because of the need to take a holistic personalistic perspective of mental health problems. The evidence for the abolition of the distinction between organic and functional mental illness does not exist and the argument for doing so by DSM-IV was flawed (see yet another previous post).

Related to this, I suspect Hyman still wants to hold on to the idea that primary mental illness will be shown to have biological aspects to its causation. Of course there's a tautological sense in which this is true, because the brain is necessary to mediate mental illness. But in the same way as we can't, or at least shouldn't, talk about our 'normal' thoughts, emotions and behaviour as being caused by the brain as such, nor should functional mental illness be described in those terms. The whole organism is the condition of its parts, and is in turn realised by them. We may be able to understand some of the reasons for functional mental illness, but these cannot be proven in a natural scientific way (see eg. previous post). We can only hope to understand formative causal influences, not efficient causes (see eg. another previous post). By contrast, brain pathology is a necessary cause of organic mental illness, such as dementia or delirium.

It's unclear to be what the next stage of the DSM review process will be, but as I've always said, proper conceptual foundations for understanding psychiatric diagnosis are needed before progress can be made.