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The risk that neurogenetic approaches may inflate the psychiatric concept of disease and how to cope with it

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Poiesis & Praxis

Abstract

Currently, there is a growing interest in combining genetic information with physiological data measured by functional neuroimaging to investigate the underpinnings of psychiatric disorders. The first part of this paper describes this trend and provides some reflections on its chances and limitations. In the second part, a thought experiment using a commonsense definition of psychiatric disorders is invoked in order to show how information from this kind of research could be used and potentially abused to “invent” new mental illnesses. It is then argued why an inference to the best explanation could provide an antidote to such attempts. The conclusion emphasises why normative criteria, such as those used to define disorders, cannot be derived from descriptive empirical results alone. While the etiology of some psychiatric diseases may be purely organic, there are many other cases where the psychiatric symptoms and the associated genotypes and phenotypes have an essentially and irreducibly external meaning that is derived from social and political factors. A limited perspective on the genes and brain of man carries the risk that psychiatry may increasingly treat the effects of other domains, although social and political solutions would be more appropriate.

Zusammenfassung

Derzeit besteht ein gesteigertes Interesse daran, genetische Informationen mit physiologischen Daten aus funktionellen bildgebenden Messungen zusammenzubringen, um den Hintergrund psychiatrischer Störungen untersuchen zu können. Der erste Teil des vorliegenden Artikels beschreibt diesen Trend und stellt Überlegungen zu dessen Möglichkeiten und Grenzen an. Im zweiten Teil wird ein Gedankenexperiment durchgeführt, bei dem eine aus dem Alltag entlehnte Definition psychiatrischer Störungen herangezogen wird um zu zeigen, wie Informationen aus diesem Forschungsansatz dazu ge- bzw. missbraucht werden können, neue psychische Erkrankungen zu “erfinden”. Es wird dafür argumentiert, wie ein Schluss auf die beste Erklärung als Gegenmittel zu solchen Versuchen dienen könnte. Das Ergebnis verdeutlicht, warum normative Kriterien, wie jene, die zur Definition von Erkrankungen verwendet werden, nicht allein aus deskriptiven empirischen Ergebnissen abgeleitet werden können. Während die Ätiologie mancher psychiatrischen Erkrankungen rein organisch sein kann, gibt es viele andere Fälle, in denen die psychiatrischen Symptome sowie die damit zusammenhängenden Genotypen und Phänotypen eine irreduzibel externe Bedeutung haben, die sich aus sozialen und politischen Faktoren ergibt. Eine eingeschränkte Perspektive auf Gen und Gehirn des Menschen birgt daher das Risiko, dass die Psychiatrie in zunehmendem Maße die Auswirkungen anderer Bereiche behandelt, obwohl hier soziale und politische Lösungen angemessener wären.

Résumé

De nos jours, nous observons un intérêt grandissant pour la combinaison des informations génétiques avec les données physiologiques, obtenues par la neuroimagerie fonctionnelle, afin d’étudier les fondements des désordres psychiatriques. La première partie de cet article décrit cette tendance et fournit quelques réflexions sur les opportunités qu’elle génère mais aussi sur ses limites. Dans la deuxième partie, un raisonnement intellectuel sur la définition commune des désordres psychiatriques est abordé afin de démontrer que les résultats de ce genre d’exercice peuvent être utilisés, voire dont on peut éventuellement abuser, pour « inventer » de nouvelles maladies mentales. Nous nous concentrons ensuite sur la raison pour laquelle une réflexion sur la meilleure explication serait nécessaire pour remédier à ces abus. En conclusion, nous insistons sur les raisons pour lesquelles les critères normatifs, comme ceux utilisés lors de la définition des désordres, ne peuvent être déduits à partir de résultats descriptifs empiriques uniquement. Bien que l’étiologie de certaines maladies psychiatriques puisse être organique, il existe bien d’autres cas où les symptômes psychiatriques ainsi que les génotypes et les phénotypes associés ont une signification essentiellement et irréductiblement externe dont l’origine se situe dans des facteurs sociaux et politiques. Une perspective limitée des gènes et du cerveau humain présente le risque que la psychiatrie traite de plus en plus les effets d’autres domaines alors que des solutions sociales et politiques seraient plus appropriées.

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Notes

  1. 1,229 citations as of 7 November 2008.

  2. Including genetic information as well, the respective group samples would have to be much larger. The specific number of subjects needed per group depends on genetic variability and effect size and thus cannot be determined with certainty in advance.

  3. In the case of neural networks, the distributed and holistic mass-action of many, if not all, of the net’s single units make it incomprehensible how it actually solves its tasks successfully. This is similar in the case of support vector machines, a more recent approach from machine learning theory that is now commonly applied to functional MRI data. In a multidimensional space (that can mean several hundred, thousands, or hundreds of thousands of dimensions) representing the features (e.g. brain activation at each particular time), a so-called hyperplane distinguishes two different classes. The number of hyperplanes needed, in turn, grows exponentially. Four different classes already require six hyperplanes. In order to distinguish 20 psychiatric diseases, 190 hyperplanes would have to be estimated reliably by the support vector machine. While this can be calculated theoretically, it is entirely unclear how well such systems could fare in practical applications for clinical purposes. A more comprehensive review of such methods, sometimes referred to as “decoding” or even “mind reading”, written for non-experts, has been provided by Schleim (2008, Chaps. 3, 4).

  4. The upcoming definition has caused a controversial debate in the course of the summer school on the concept of psychiatric disease, held from 2 to 9 October, 2008 in Bonn, for which an earlier draft of this paper was submitted. In order to avoid an intermixture with philosophical Pragmatism, it is now called a “commonsense” instead of a “pragmatic” definition. Furthermore, all elements are to be understood as a conjunction, if that is not already clear by the structure of the sentence. Finally, it should be noted that there are certainly researchers who spent much more time on more sophisticated trials to define what a psychiatric disorder is, while this commonsense definition is based on interviews with psychiatrists in Germany and a historical perspective from the USA (Friedman et al. 1976).

  5. The thought experiment has so far not referred to any genetic information which played a major part in the paper’s first section. Assuming that certain personality traits, such as a willingness to spend additional hours on work (perhaps related to a higher degree of conscientiousness), depend on the genotype, it is easy to describe the example with reference to a genotype instead of an endophenotype, or both, mutatis mutandis.

  6. We have of course neglected conditions (5) and (6) hitherto; for the sake of the counterargument, let us assume that the thought experiment passes these criteria, too. These conditions will be addressed later.

  7. It would actually pose a severe theoretical problem to neuroscientists if they could not find such endophenotypes. This hypothetical case implies that a difference on the mental level–e.g. different levels of fatigue–is not accompanied by differences on the physical level (in the brain). This would violate the supervenience constraint considered as a minimal requirement of physicalism by philosophers of the mind (Kim 2005).

  8. In the Diagnostic and Statistic Manual (DSM) of the American Psychiatric Association published in 1952, it was actually listed under “sociopathic personality disturbances.” This changed in the edition of 1968, where it was “merely” considered a mental disorder.

  9. This is also relevant to legal cases where defendants may try to use a deviation from “normal” brain activity or structure to make a diminished responsibility excuse. Michael Gazzaniga has used the exclamation “My brain made me do it!” to caricature this effort (Gazzaniga 2005; p 87). This is not to say that abnormal brain activation or structure could not be used for such an excuse, but to provide an example that normative demands cannot be derived from descriptive data alone.

  10. Jorge Ponseti, the principal investigator, considers his findings as proof for a biological disposition to homosexual orientation (personal communication, 26 September 2006). However, whether a condition is biologically disposed or not does not help to distinguish between health and disease. Many illnesses are biologically disposed. Furthermore, investigating brain activity does not provide evidence for biological disposition, since non-biological environmental influences including culture are, of course, just as reflected in brain function and structure as the effects of reading and speaking on brain areas associated with language comprehension and production demonstrate. Thus, Ponseti would have to search for neurogenetic interactions in order to support his claim.

  11. We know the subjects are overworked and tired; we also know that overwork usually and naturally leads to fatigue. Furthermore, from research in cognitive psychology, we know that tired subjects perform worse in certain behavioural tasks and from reasonable assumptions concerning the relation between mental states and brain states it follows that fatigue is associated with particular changes in the functioning of the brain. Thus, we have a causal account of why the target subjects in the thought experiment are tired and hence perform worse as well as a reasonable explanation for the measured functional endophenotype. Introducing the notion of a “subwakefulness syndrome” does not add anything to the explanation; by contrast, it leaves the fact that the subjects are overworked entirely unconnected to the other observations. This illustrates that abductions are relative to the available knowledge and that it is important to look for other observations and hypotheses which explain the empirical data better than the “invention” of a new mental disorder; more sophisticated examples than can be discussed here can be found in Barteborth’s monography on the topic of explanatory strategies (Bartelborth 2002).

  12. It must be noted that I have developed these thoughts from an outsider's perspective. While I am employed at a psychiatric clinic, I have never been involved, not even as an observer, in clinical practice, nor is it likely that I ever will be. Thus, the little I know about psychiatric practice is derived from descriptions in textbooks and discussions with psychiatrists.

  13. I am indebted to my colleagues and Thomas Wienker for their sustained support and critical suggestions concerning my work. While my thoughts about the future of psychiatry rely on their help, they do not necessarily reflect their opinions. Furthermore, mistakes in my arguments are due solely to my own misunderstanding.

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  1. Division of Medical Psychology, Department of Psychiatry, University Clinics Bonn, Sigmund-Freud-Straße 25, 53105, Bonn, Germany

    Stephan Schleim

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Correspondence to Stephan Schleim.

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Schleim, S. The risk that neurogenetic approaches may inflate the psychiatric concept of disease and how to cope with it. Poiesis Prax 6, 79–91 (2009). https://doi.org/10.1007/s10202-008-0066-y

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