What will the RDoC initiative by NIMH achieve?
There's a lot wrong with current psychiatric classification. Every few years, the American Psychiatric Association comes up with a new set of labels and diagnostic criteria, but whereas the Diagnostic and Statistical Manual used to be seen as some kind of Bible for psychiatrists, the latest version, DSM5, has been greeted with hostility and derision. The number of diagnostic categories keeps multiplying without any commensurate increase in the evidence base to validate the categories. It has been argued that vested interests from pharmaceutical companies create pressures to medicalise normality so that everyone will sooner or later have a diagnosis (Frances, 2013). And even excluding such conflict of interest, there are concerns that such well-known categories as schizophrenia and depression lack reliability and validity (Kendell & Jablensky, 2003).
In 2013, Tom Insel, Director of the US funding agency, National Institute of Mental Health (NIMH), created a stir with a blogpost in which he criticised the DSM5 and laid out the vision of a new Research Domain Criteria (RDoC) project. This aimed "to transform diagnosis by incorporating genetics, imaging, cognitive science, and other levels of information to lay the foundation for a new classification system."
He drew parallels with physical medicine, where diagnosis is not made purely on the basis of symptoms, but also uses measures of underlying physiological function that help distinguish between conditions and indicate the most appropriate treatment. This, he argued, should be the goal of psychiatry, to go beyond presenting symptoms to underlying causes, reconceptualising disorders in terms of neural systems.
This has, of course, been a goal for many researchers for several years, but Insel expressed frustration at the lack of progress, noting that at present: "We cannot design a system based on biomarkers or cognitive performance because we lack the data". That being the case, he argued, a priority for NIMH should be to create a framework for collecting relevant data. This would entail casting aside conventional psychiatric diagnoses, working with dimensions rather than categories, and establishing links between genetic, neural and behavioural levels of description.
This represents a massive shift in research funding strategy, and some are uneasy about it. Nobody, as far as I am aware, is keen to defend the status quo, as represented by DSM. As Insel remarked in his blogpost: "Patients with mental disorders deserve better". The issue is whether RDoC is going to make things any better. I see five big problems.
1. McLaren (2011) is among those querying the assumption that mental illnesses are 'disorders of brain circuits'. The goal of the RDoC program is to fill in a huge matrix with new research findings. The rows of the matrix are not the traditional diagnostic categories: instead they are five research domains: Negative Valence Systems, Positive Valence Systems, Cognitive Systems, Systems for Social Processes, Arousal/Regulatory Systems, each of which has subdivisions: e.g. Cognitive Systems is broken down into Attention, Perception, Working memory, Declarative memory, Language behavior and Cognitive (effortful) control. The columns of the matrix are Genes, Molecules, Cells, Circuits, Physiology, Behavior, Self-Reports, and Paradigms. Strikingly absent is anything about experience or environment.
This seems symptomatic of our age. I remember sitting through a conference presentation about a study investigating whether brain measures could predict response to cognitive behaviour therapy in depression. OK, it's possible that they might, but what surprised me was that no measures of past life events or current social circumstances were included in the study. My intuitions may be wrong, but it would seem that these factors are likely to play a role. My impression is that some of the more successful interventions developed in recent years are based not on neurobiology or genetics, but on a detailed analysis of the phenomenology of mental illness, as illustrated, for example, by the work of my colleagues David Clark and Anke Ehlers. Consideration of such factors is strikingly absent from RDoC.
2. The goal of the RDoC is ultimately to help patients, but the link with intervention is unclear. Suppose I become increasingly obsessed with checking electrical switches, such that I am unable to function in my job. Thanks to the RDoC program, I'm found to have a dysfunctional neural circuit. Presumably the benefit of this is that I could be given a new pharmacological intervention targeting that circuit, which will make me less obsessive. But how long will I stay on the drug? It's not given me any way to cope with the tendency of checking the unwanted thoughts that obtrude into my consciousness, and they are likely to recur when I come off it. I'm not opposed to pharmacological interventions in principle, but they tend not to have a 'stop rule'.
There are psychological interventions that tackle the symptoms and the cognitive processes that underlie them more directly. Could better knowledge of neurobiological correlates help develop more of these? I guess it is possible, but my overall sense is that this translational potential is exaggerated – just as with the current hype around 'educational neuroscience'. The RDoC program embodies a mistaken belief that neuroscientific research is inherently better than psychological research because it deals with primary causes, when in fact it cannot capture key clinical phenomena. For instance, the distinction between a compulsive hand-washer and a compulsive checker is unlikely to have a clear brain correlate, yet we need to know about the specific symptoms of the individual to help them overcome them.
3. Those proposing RDoC appear to have a naive view of the potential of genetics to inform psychiatry. It's worth quoting in detail from their vision of the kinds of study that would be encouraged by NIMH, as stated here:
Recent studies have shown that a number of genes reported to confer risk for schizophrenia, such as DISC1 (“Disrupted in schizophrenia”) and neuregulin, actually appear to be similar in risk for unipolar and bipolar mood disorders. ... Thus, in one potential design, inclusion criteria might simply consist of all patients seen for evaluation at a psychotic disorders treatment unit. The independent variable might comprise two groups of patients: One group would be positive and the other negative for one or more risk gene configurations (SNP or CNV), with the groups matched on demographics such as age, sex, and education. Dependent variables could be responses to a set of cognitive paradigms, and clinical status on a variety of symptom measures. Analyses would be conducted to compare the pattern of differences in responses to the cognitive or emotional tasks in patients who are positive and negative for the risk configurations.
This sounds to me like a recipe for wasting a huge amount of research funding. The effect sizes of most behavioural/cognitive genetic associations are tiny and so one would need an enormous sample size to see differences related to genotype. Coupled with an open-ended search for differences between genotypes on a battery of cognitive measures, this would undoubtedly generate some 'significant' results which could go on to mislead the field for some time before a failure to replicate was achieved (cf. Munafò, & Gage, 2013).
The NIMH website notes that "the current diagnostic system is not informed by recent breakthroughs in genetics". There is good reason for that: to date, the genetic findings have been disappointing. Such associations as are found either indicate extremely rare and heterogeneous mutations of large effect and/or involve common genetic variants whose small effects are not of clinical significance. We cannot know what the future holds, but to date talk of 'breakthroughs' is misleading.
4. Some of the entries in the RDoC matrix also suggest a lack of appreciation of the difference between studying individual differences versus group effects. The RDoC program is focused on understanding individual differences. That requires particularly stringent criteria for measures, which need to be adequately reliable, valid and sensitive to pick up differences between people. I appreciate that the published RDoC matrices are seen as a starting-point and not as definitive, but I would recommend that more thought goes into establishing the psychometric credibility of measures before embarking on expensive studies looking for correlations between genes, brains and behaviour. If the rank ordering of a group of people on a measure is not the same from one occasion to another, or if there are substantial floor or ceiling effects, that measure is not going to be much use as an indicator of an underlying construct. Furthermore, if different versions of a task that are supposed to tap into a single construct give different patterns of results, then we need a rethink – see e.g. Foti et al, 2013; Shilling et al, 2013, for examples. Such considerations are often ignored by those attempting to move experimental work into a translational phase. If we are really to achieve 'precision medicine' we need precise measures.
5. The matrix as it stands does not give much confidence that the RDoC approach will give clearer gene-brain-behaviour links than traditional psychiatric categories.
For instance, BDNF appears in the Gene column of the matrix for the constructs of acute threat, auditory perception, declarative memory, goal selection, and response selection. COMT appears with threat, loss, frustrative nonreward, reward learning, goal selection, response selection and reception of facial communication. Of course, it's early days. The whole purpose of the enterprise is to flesh out the matrix with more detailed and accurate information. Nevertheless, the attempts at summarising what is known to date do not inspire confidence that this goal will be achieved.
After such a list of objections to RDoC, I do have one good thing to say about it, which is that it appears to be encouraging and embracing data-sharing and open science. This will be an important advance that may help us find out more quickly which avenues are worth exploring and which are cul-de-sacs. I suspect we will find out some useful things from the RDoC project: I just have reservations as to whether they will be of any benefit to psychiatry, or more importantly, to psychiatric patients.
Foti, D., Kotov, R., & Hajcak, G. (2013). Psychometric considerations in using error-related brain activity as a biomarker in psychotic disorders. Journal of Abnormal Psychology, 122(2), 520-531. doi: 10.1037/a0032618
Frances, A. (2013). Saving normal: An insider's revolt against out-of-control psychiatric diagnosis, DSM-5, big pharma, and the medicalization of ordinary life. New York: HarperCollins.
Kendell, R., & Jablensky, A. (2003). Distinguishing between the validity and utility of psychiatric diagnoses. American Journal of Psychiatry, 160, 4-12.
McLaren, N. (2011). Cells, Circuits, and Syndromes: A Critical Commentary on the NIMH Research Domain Criteria Project Ethical Human Psychology and Psychiatry, 13 (3), 229-236 DOI: 10.1891/1559-43188.8.131.52
Munafò, M. R., & Gage, S. H. (2013). Improving the reliability and reporting of genetic association studies. Drug and Alcohol Dependence(0). doi: http://dx.doi.org/10.1016/j.drugalcdep.2013.03.023
Shilling, V. M., Chetwynd, A., & Rabbitt, P. M. A. (2002). Individual inconsistency across measures of inhibition: an investigation of the construct validity of inhibition in older adults. Neuropsychologia, 40, 605-619.
This article (Figshare version) can be cited as:
Bishop, Dorothy V M (2014): Changing the landscape of psychiatric research: What will the RDoC initiative by NIMH achieve?. figshare. http://dx.doi.org/10.6084/m9.figshare.1030210