Will Biology Tell Us All We Need to Know About Mental Disorder?

In July 2009, the NIMH hosted a meeting with the World Health Organization and the American Psychiatric Association at which it launched its research program for the foreseeable future.¹ The Research Domain Criteria (RDoC) project is intended to replace the former framework, Research Diagnostic Criteria, that formed the basis of the DSM system over a number of iterations.

RDoC is essentially a laboratory-based program directed at seeing mental disorder in biological terms: “First, the RDoC framework conceptualizes mental illnesses as brain disorders . . . mental disorders can be addressed as disorders of brain circuits. . . . Second, . . . the dysfunction in neural circuits can be identified with the tools of clinical neuroscience, including electrophysiology, functional neuroimaging, and new methods for quantifying connections in vivo. Third, . . . data from genetics and clinical neuroscience will yield biosignatures that will augment clinical symptoms and signs for clinical management.” Essentially, RDoC will transform psychiatry into a clinical neuroscience.

In introducing this major reorientation, Thomas Insel, Director of NIMH, warned that it represents a huge investment of time, effort, and necessarily, of money, and it would be unrealistic to expect even preliminary results in under a decade: “We are still a long way from knowing if this approach will succeed. . . . We recognize that the creation of such a new approach is a daunting task, which will likely require several mid-course corrections and may ultimately fail to deliver the transformation we seek in clinical care.”

This message has been repeated in influential journals and widely read periodicals.^2-6 The program itself has been criticized as unachievable, but that is a separate issue.⁷ My concern here is the claim that biology can tell us everything we need to know about mental disorder, with no questions unanswered: “One of the fundamental insights emerging from contemporary neuroscience is that mental illnesses are brain disorders.”⁸ Indeed, the entire success of this program and most of the current research in psychiatry hinges on this claim.

To our lasting humiliation, psychiatry has already had 1 or 2 “lost generations,” when all our efforts were directed toward the wrong goal. It is worth noting that the problems inherent in psychoanalysis and behaviorism were known many years before psychiatrists finally relented and abandoned their dreams. In 1922, Popper had demonstrated that psychoanalysis was not and could not be scientific, while Chomsky’s remarkable dissection of Skinner’s theories in 1959 will never be outdated.⁹ Therefore, before the profession commits to the biological path, we should be certain of our intellectual grounds.

In brief, the central issue is the claim that all mental disorders are, in some essential sense, brain disorders (that brain disorder is both necessary and sufficient for mental disorder). I began to check the references in each of the articles cited above (and many others of the same nature). To my surprise, the bold claims were never referenced. Instead, they are presented as flat statements, as though utterly beyond question. I found this rather strange. In any other science, it is possible to track back through the references to find the earliest discoveries that set the discipline on that particular course.

For example, it is easy to find the first articles from the early 1980s describing a strange and deadly new immune deficiency. Similarly, every basic medical and physiology text will refer to Banting and Best, to Ramon y Cajal, Fleming, and so many others (and rightly so: it is highly appropriate that medical students study the greats). However, despite poring over these articles, checking each reference then each author’s publication list, it seems modern psychiatry is not following in the footsteps of our medical brethren: we alone have no history. Who proved that mental disorder is just brain disorder? Nobody seems to have examined this vital point.

This question has troubled me for years: If we claim to know the nature of mental disorder, what exactly are we assuming? No proposition exists in isolation. Every belief comes nested in earlier beliefs, explicit and implicit, each of which has to be understood clearly so that bias can be detected and eliminated. Yet here, at the very heart of psychiatry, people seem totally unconcerned about making claims that, for example, philosophers have never been able to prove. What are the options? The first explanation is that as a matter of strict identity, mental disorder is just a brain disorder. This reflects a theory from the 1950s and 1960s-the Mind-Brain Identity Theory (MBIT). In fact, it could only make sense in psychiatry if the MBIT itself were true. Nobody accepts this now, as I showed in 1992, and it is rare for people to claim it for psychiatry.¹⁰

The next option is that mental disorder can be reduced to brain disorder. The concept of reductionism is absolutely basic to Western science; it has been the most successful scientific program in human history and is nowhere near reaching its end. In psychiatry, it would be a case of mental disorder reducing to brain disorder. This would be part of a broader program, or reducing mind to brain; unfortunately, there is no support for the notion that the phenomena of mind can be explained in terms of the phenomena of physical science.¹¹ Philosophers have moved on because the properties of molecules do not explain the properties of the entities constructed from them.

It is clear that explaining mental disorder depends on explaining mind: we need an account of normal mental function before we can give account to abnormal function. In philosophy, there are not many options. Functionalism, the dominant theory of mind, says nothing about mental disorder. The most popular form of functionalism, from the philosopher Daniel Dennett, offers no clues as to how mental disorder may arise. I have argued that his program is at an end, just because it is covertly dualist in nature, so anybody wishing to use his work to explain mental disorder would be wise to take this into account.¹² This also applies to other theories of mind, but that is not germane to the question of whether psychiatrists have explained why a research program in mental disorder devolves to a research program in the neurosciences.

Eventually, I surveyed 11 of the most influential English-language journals in psychiatry, from January 2001 to December 2011.¹³ This yielded some 1465 issues totalling 154,000 pages. If the explanation of why mental disorder is a form of brain disorder lies anywhere, it should be somewhere in that very large pile. There were something like 19,250 original research papers, editorials, commentaries, reviews, surveys, and opinions, including every significant figure in psychiatry today. I found nothing to indicate that any person of any stature in modern psychiatry has offered anything that would justify the belief expressed above: “. . . mental illnesses are brain disorders.”⁸ This proposition is an opinion, but it is nothing more than opinion. In fact, opinions held very firmly without formal justification amount to an ideology.

At this stage of its development, biological psychiatry amounts to an ideology, and no more. It does not have a theory of mind and it has no formal model of mental disorder, no theory of personality or personality disorder, and no understanding of how these concepts would fit together. The claim that mental disorder is brain disorder is not a theory of mental disorder because it has no basis in a broader understanding of what constitutes science.

This is very important, because it says all our claims to have a solid intellectual grip on the nature of mental disorder, sufficient to launch a 20- to 30-year research program at $1.5 billion a year, lack the most elementary intellectual basis. We are, in fact, heading down the same path as the psychoanalysts and behaviorists: we are launching a massive scientific research program without first examining the nested beliefs on which that program depends. Yes, by chance, it may turn out to be correct, but that is not, I suggest, sufficient basis for this type of program. People’s lives depend on it. In general medicine, we demand the most stringent intellectual standards, yet in psychiatry, we rely on opinions.

People sometimes refer to articles by Samuel Guze¹⁴ from several decades ago in which he expressed the belief that there cannot be a psychiatry that is too biological. In fact, there can be: any attempt to explain language in biological terms will fail, as philosophers have long argued (for example, see Chomsky¹⁵). Others refer to the neurophysiologist Eric Kandel,¹⁶ who has repeatedly stated that neurosciences will give an account of mental disorder by some program he calls “radical reductionism.” Again, he offers nothing more than opinion, unsupported by anything that would amount to a cogent argument.¹⁷ Within neurophysiology, his opinions are worth noting; outside his discipline, they carry no more weight than those of other “greats” who have been proved wrong (Lord Kelvin, for example, believed that the sun would not last long enough for evolution to occur; he assumed the sun was made of coal).

This gloomy conclusion is not popular, and psychiatrists who have devoted their careers to exploring the biology of mental disorder often react with resentment. That is their problem; I am merely the messenger, the little boy who said, “But the emperor is wearing no clothes.” Rather than argue, I leave it with them: Please give me the name of the model of mental disorder you use in your daily practice, your teaching and your research, and provide me with 3 seminal references where it is articulated as a series of testable propositions that meet the minimal standards of our modern concept of a scientific theory.

Nobody has ever done it, but until somebody does, psychiatry could well be on the wrong path. I think we should sort out whether biological psychiatry has a formal basis in science before we spend another penny on it.

Disclosures:

Dr McLaren is Psychiatrist with the Northern Psychiatric Services of Brisbane, Queensland, Australia. He reports no conflicts of interest concerning the subject matter of this article.

References:

1. Insel T, Cuthbert B, Garvey M, et al. Research Domain Criteria (RDoC): toward a new classification framework for research on mental disorders. Am J Psychiatry. 2010;167:748-751.

2. Cuthbert BN, Insel TR. Toward new approaches to psychotic disorders: the NIMH Research Domain Criteria project. Schizophr Bull. 2010;36:1061-1062.

3. Insel TR, Freund M. Shedding light on brain circuits. Biol Psychiatry. 2012;71:1028-1029.

4. Morris SE, Cuthbert BN. Research Domain Criteria: cognitive systems, neural circuits, and dimensions of behavior. Dialogues Clin Neurosci. 2012;14:29-37.

5. Yan J. NIMH builds new framework for understanding mental illness. Psychiatr News. 2010;45:9.

6. Insel TR. Faulty circuits. Sci Am. April 2010;302:44-51.

7. McLaren N. Cells, circuits and syndromes: a critical commentary on the NIMH Research Domain Criteria project. Ethical Hum Psychol Psychiatry. 2011;13:229-236.

8. Insel TR, Quirion R. Psychiatry as a clinical neuroscience discipline. JAMA. 2005;294:2221-2224.

9. Chomsky N. A Review of B. F. Skinner’s Verbal Behavior. Language. 1959;35:26-58.

10. McLaren N. Is mental disease just brain disease? The limits to biological psychiatry. Aust N Z J Psychiatry. 1992;26:270-276.

11. McLaren N. The irreducible mentality of mind. In: The Mind-Body Problem Explained: The Biocognitive Model for Psychiatry. Ann Arbor, MI: Future Psychiatry Press; 2012:3-18.

12. McLaren N. Emergent logic and antimonism. In: The Mind-Body Problem Explained: The Biocognitive Model for Psychiatry. Ann Arbor, MI: Future Psychiatry Press; 2012:21-41.

13. McLaren N. Psychiatry as ideology. Ethical Hum Psychol Psychiatry. 2013;15:7-17.

14. Guze SB. Biological psychiatry: is there any other kind? Psychol Med. 1989;19:315-323.

15. Chomsky N. New Horizons in the Study of Language and Mind. New York: Cambridge University Press; 2000.

16. Kandel ER. Psychiatry, Psychoanalysis, and the New Biology of Mind. Washington, DC: American Psychiatric Publishing; 2005.

17. McLaren N. Defining limits to biological reductionism. In: Humanizing Psychiatry: The Biocognitive Model. Ann Arbor, MI: Future Psychiatry Press; 2009:1-21.