Mental Disorders in Entangled Brains
Commentary in Philosophical Psychology
My peer-reviewed commentary “Mental disorders in entangled brains” on Anneli Jefferson’s book Are Mental Disorders Brain Disorders? has been published online ahead of print in Philosophical Psychology (feel free to email me for a pdf copy if you don’t have access).
The commentary is based on two prior posts, linked below, from Psychiatry at the Margins, so many readers will be familiar with the substance of the argument. I will offer a synopsis of my view in this post, and share some pertinent excerpts from my article.
The philosophical understanding of psychiatric disorders as brain disorders that I offer, as an outcome of my engagement with Jefferson’s excellent book, is as follows:
I agree with Jefferson that both the “narrow view” (dysfunction in the brain must be identifiable independently of the psychological symptoms, the dysfunction must causally precede mental symptoms, and treatment must directly target the brain) and the “broad view” (the assumption that whatever is going on in the brain that is producing dysfunctional psychological processes must itself be dysfunctional) of brain disorders are problematic.
I agree with Jefferson that the characterization of a brain difference as dysfunctional may be dependent on the presence of psychological dysfunction. For psychiatric conditions, the hard work of figuring out whether something is dysfunctional, or a “disorder,” still has to be done in psychological terms with reference to psychological norms. Merely pointing to a systematic brain difference won’t settle that question. Without reference to a psychological dysfunction, we may not be able to characterize the systematic brain difference as dysfunctional. This dependency of brain dysfunction on mental dysfunction is crucial to acknowledge.
I agree with Jefferson that if mental disorders are brain disorders, this should require empirical demonstration. We should be able to identify the relevant brain differences. We cannot simply assume that what exists as a coherent category or construct in psychological terms corresponds to a coherent category or construct in neurological terms.
Although Jefferson endorses Cummins’s account of dysfunction in the book, her account (and mine) is actually compatible with a wide range of notions of psychological dysfunction. We can therefore be, and I think we should be, pluralists about dysfunction.
“The basic requirement is that there ought to be identifiable differences in the brain that realize a particular psychological state that we have characterized as a psychological dysfunction. Whether such identifiable brain differences exist or not for a particular psychological state is independent of whether we call that psychological state a dysfunction or not.”
I disagree with Jefferson’s criterion of sufficiency. According to Jefferson, a mental dysfunction must correspond to a brain difference that we can identify, and this brain difference must be sufficient for the psychological difference to be experienced or observed; the brain difference identified must always be accompanied by the relevant psychological state. The sufficiency requirement strikes me as very arduous, to a point where I am uncertain that it can be practically met for any paradigmatic mental disorder. And if it cannot be met, except in rare circumstances, it undermines the scientific utility of Jefferson’s notion.
I propose that we can consider the following as another Goldilocks solution to the justification question: we are justified in calling a psychological dysfunction a brain dysfunction if there are substantial, reliable, and systematic brain differences associated with the psychological dysfunction.
“The problem is that if neuroscientists such as Pessoa, Feldman Barrett, and Mitchell are correct, this stringent criterion of sufficiency is impossible in practice. Our best neuroscientific understanding of the brain-behavior relationship tells us that this sort of sufficient one-to-one correspondence, as a matter of general principle, is going to be the exception rather than the rule. An account of brain disorders that fails to take this into account just isn’t going to be very useful.”
“What can we reasonably expect? Similar to Mitchell, I think we can expect differential involvement of brain functions in different psychiatric disorders, expressed, for example, with reference to brain networks and their dynamic activity, or even expressed in neurocomputational terms. These associations may not be necessary or sufficient; they may not even be highly specific. But they can be systematic, substantial, and reliable, and allow for the increased neuroscientific understanding of the etiology of mental disorders and better development of neurotherapeutics.”
“The relationship is such that it involves many areas of the brain, there is no one-to-one mapping, and emotions emerge from a computational process that involves complex dynamic interactions in a highly context dependent manner (Barrett, 2017). This theoretical framework of the brain-behavior relationship is crucial for mental disorders as well.”
The crux of my view of mental disorders as brain disorders:
“This, in my opinion, is the crux of the mental-disorders-are-brain-disorders project: a psychiatric disorder can be said to be a brain disorder if there are empirically identifiable systematic brain differences associated with it and these associations are contextualized within a scientifically robust theoretical understanding of the relationship between brain and behavior.
Consistent with the spirit of Jefferson’s account, this is still an empirical matter. It is an open scientific question whether this goal will be achieved and for which conditions. It is also a goal that meaningfully aligns with the research agenda of biological psychiatry and frameworks such as the RDoC. And it reminds us that the question of the neurobiological basis of psychopathology cannot be divorced from a broader neuroscientific understanding of the brain-behavior relationship.”
I end with some reflections on whether the assertion that mental disorders are brain disorders may simply be an aspiration (or an assumption) that one day we will describe, explain, and understand mental disorders using the language of neuroscience, with no restrictions on the shape and form this language may take in the future.
“… the development of computational psychiatry is reflective of the theoretical evolution of neuroscience. In some ways perhaps, the issue of “mental disorder” versus “brain disorder” comes down to the language of psychology – ordinary as well as clinical – versus the language of neuroscience, and the degree to which the former can be expressed in the latter. In the past, neuroscience has been limited by methods available (e.g., structural and functional neuroimaging), but the embrace of complex systems, network theories, and computational approaches opens up new possibilities of translation. Such a neuroscience would have to meaningfully tackle mental phenomena such as consciousness, intentionality, agency, and normativity, and we are not quite there yet. The fundamental motivation behind “mental disorders are brain disorders” may be something as simple as: one day we will describe, explain, and understand mental disorders using the language of neuroscience. The key limitation is that it cannot simply be assumed that this scientific undertaking will be successful. The relationships may be far too complex to be tractable – we only have to look to genetics to appreciate that – and neither confidence nor faith will serve us well. Jefferson’s work is a powerful reminder that a metaphysical commitment to physicalism is not an adequate justification for us to call mental disorders as brain disorders. There are several ways in which a better justification might be worked out; Jefferson offers a justification based on realization and sufficiency, and I’ve offered answers of my own to the justification question, but we are united in the sentiment that an empirical demonstration is necessary. Neuroscience has to actually deliver the goods and show us the receipts.”
This, in my opinion, is the crux of the mental-disorders-are-brain-disorders project: a psychiatric disorder can be said to be a brain disorder if there are empirically identifiable systematic brain differences associated with it and these associations are contextualized within a scientifically robust theoretical understanding of the relationship between brain and behavior.
P.S. The “entangled” in the title is borrowed from Luiz Pessoa’s 2022 book The Entangled Brain. “Entangled” refers to the dynamic and highly context-dependent interactions of different brain regions. Pessoa understands the brain as a complex system where organizational relationships and dynamic interactions lead to novel collective properties.
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