Are Mental Disorders Brain Disorders?

Anneli Jefferson

Reviewed by Dominic Murphy

Are Mental Disorders Brain Disorders?
Anneli Jefferson
London: Routledge, 2022, £48.99
ISBN 9780367421380

It is greatly to the credit of Anneli Jefferson that she has managed to write a book on this oft-discussed topic that is actually interesting. It is also short and readable, twin virtues that make it an easy recommendation for anyone looking for a way into the debate or for a text to assign students. Jefferson moves fluently through the intellectual terrain, objecting to some versions of what ‘brain disorder’ might mean, before proposing her own version and then discussing the implications of her account for questions of agency and moral responsibility. This final discussion on issues around moral responsibility is likely to make the book especially attractive for students and practitioners who want not just to learn about the metaphysics of psychopathology but also to get a wider sense of why it matters, and to connect the ontology with moral psychology. Philosophers of psychiatry are building connections with phenomenology and also looking for relevance in more applied areas, and the last chapter of the book will help anyone starting out to understand the literature connecting philosophical psychopathology with debates over agency and moral responsibility. I recommend that chapter heartily. Like much of the book, it is a model of clear, painstaking discussion of the issues, and you will benefit from reading it. I am going to focus, though, on the debate over whether mental disorders are brain disorders, which forms the core of the book.

Jefferson thinks this debate has been distorted by the widespread and largely unthinking adoption of what she calls ‘the narrow view of brain disorders’. The narrow view says that a brain disorder is a neurological defect that can be identified ‘by biological science alone’ (p. 10). Paradigmatic conditions of this kind include brain cancers and the lesions associated with dementia and neurosyphilis. These conditions, Jefferson thinks, are often used as the basis for ostensive definitions of brain disorders—brain disorders are things like this—and she puts the blame for the dominance of this view on Thomas Szasz. Szsaz challenged psychiatry to validate its diagnoses, but based the challenge on the view that biological lesions are the only legitimate markers of disease. Because psychiatry has found no such conditions, he asserted, it has no valid diagnoses. Although he also thought that if we did find such conditions, then they would not be psychiatric, because then they would have been shown to be physical.

Szasz seems to have been an eliminativist about the mental, but we can see him as part of a more general embrace of physicalism that makes the idea of mental disorders as brain disorders attractive. Jefferson thinks that although most theorists rejected Szasz’s conclusions, they did accept his premises, or at least they accepted his view of what makes something a legitimate disorder. This reductive view represents what Jefferson sees as the excessively narrow view of mental illness as brain dysfunction. She is right to conclude that it can do nothing but point to paradigm cases and has no resources to clearly define them (p. 38). I think she is on less firm ground, though, when she claims that it ‘neglects the fact that for many mental and brain disorders physiological, psychological and environmental factors affect both the onset and the treatment of the condition’ (p. 38). If you take the reductive view of mental disorders as brain disorders, it is likely that you follow Szasz in thinking that the paradigmatic disease concept is that of a destructive physiological process. These can take different forms, of course, but they seem compatible with environmental causes and influences. Perhaps this turns on whether we see pathophysiology as the realizer or the cause of mental illness; Jefferson is happy with either (p. 44), but I think even an arch-reductionist could admit of non-biological causes of a physical realization. This takes us to the second view Jefferson wants to dissent from, namely, the overly broad view that sees any mental disorder as a brain disorder. Her dissent here rests on a commitment to multiple realization as a mind–body doctrine.

Jefferson’s positive proposal about the nature of mental disorder is that a psychological dysfunction does not entail the existence of a corresponding brain dysfunction but is autonomous, in that it can be established without attention to the brain. But it will be realized in some brain system—and these brain systems are pathological because they realize psychological dysfunctions. So the psychology is in charge in these cases. (There can be other pathological brain systems that have no psychological import.) Jefferson regards this as a departure from the over-inclusive view that says that mental disorders just are brain disorders because of her insistence on ‘stable realizing processes’. She demands this because of metaphysical scruples—there are varieties of both dualism and non-reductive physicalism that would refute the over-inclusive view. In particular, her view is that multiple realizability entails that there are mental dysfunctions that do not have stable realizers. I am unsure about this.

Here is a metaphysical thesis: mental processes can be realized in ever so many different ways, so that an alien, a robot, or a non-human animal can exhibit recognizable mental life even if they are made of very different stuff. And here is an empirical claim about human beings: we can share mental processes even though we differ from one another just as much as we differ from robots, dragonflies, or bug-eyed tentacled aliens. I like the metaphysical thesis, but I do not think the concept of multiple realization that features in the mind–body problem as a rebuttal to type-identity theories is a useful empirical claim about human psychology. Functionalism is a metaphysical thesis, not a theory about humans. It may be helpful to know that cocaine interferes with memory consolidation in honey bees despite their other-than-human neuroanatomy (Sovik et al. [2018]). This certainly suggests that memory dysfunctions are multiply realizable. But do generalizations across human addicts need to hold across such diverse systems? Well, no, because people who deal with human addicts are not interested in bees and don’t build theories to include them. But what about Jefferson? When she stresses the significance of multiple realization, just how multiple are we talking? I don’t think Jefferson ever really gets clear on this point. She mentions that some mental illnesses may correspond to different brain anomalies (p. 41), but I don’t know how different a brain anomaly has to be, on this account, for it to threaten the claim that mental disorders are brain disorders. I think the view is that if the neural realizer of a dysfunction is too disjunctive, then there is not really any brain disorder at all. But I find the discussion of this issue mixes up what we might think of as proper metaphysics—the metaphysics of mind—with more empirical questions about the prospects for reductive explanation in philosophy of psychology. Other readers might like this feature of the discussion, but I was frustrated by it. I think this is because I am on the other side of what Jefferson thinks of as a very profound intellectual divide (p. 44), separating her from proponents of the over-inclusive view. That view, she thinks, makes no empirical claims and is just (wrongly) supposed by its proponents to be a straightforward derivation from physicalism.

I think this is almost entirely correct and I am grateful to Jefferson for putting the issue so starkly. I would put it like this: What she calls the over-inclusive does little more than commit us to studying mental disorders as continuous with the other sciences of the mind, in that they all aim ultimately at mechanistic explanations of properties of intelligent systems, since we have learned that treating the world—including its human components—as unedifying collections of machines is the right way to do natural philosophy. This is sort of an empirical claim, in that it claims legitimacy based on the history of modern inquiry into nature. But it doesn’t make any particular predictions and it has no independent non-contingent foundations.

The appeal of this picture in psychiatry has always been its affiliation with the sciences of the nervous system. A somewhat jaded view is that this just shows the desire of psychiatry to look like proper science. But there really is a kind of methodological promise on offer if we try to copy sciences that seem to get it right. Perhaps it is simply that the label of ‘brain disease’ is more of a philosophical commitment to a materialist and biologicist picture of humans than a basis for a method, but I think that’s satisfactory, since the point of a research programme is in part to confer a shared identity on the community it defines. I think philosophers like Jefferson worry that this approach lacks the foundations that a proper metaphysical discussion would provide. But some of us don’t care about foundations.

Dominic Murphy
University of Sydney
dominic.murphy@sydney.edu.au

References

Søvik, E., Berthier, P., Klare, W. P., Helliwell, P., Buckle, E. L. S., Plath, J. A., Barron, A. B. and Maleszka, R. [2018]: ‘Cocaine Directly Impairs Memory Extinction and Alters Brain DNA Methylation Dynamics in Honey Bees’, Frontiers in Physiology, 9, available at doi.org/10.3389/fphys.2018.00079.