But first we had better take a look at the RDoC project. The project has its origin in the failure of DSM-III and DSM-IV to achieve their ultimate scientific objectives. In the planning of DSM-III, the first objective was to insure reliability of the diagnostic constructs across different research and clinical settings through the use of diagnostic criteria. That goal was mostly accomplished and was considered the main achievement of DSM-III and DSM-IV.
A second objective was to achieve validity of the diagnostic categories—that the categories would reflect real disease or disorder entities in the real world. The current consensus is that this goal has not been not been achieved. Warning signs have been the heterogeneity of clinical presentation, high levels of comorbidity, overlapping of categories, and failure to discover biological markers for the diagnostic categories. In a more technical sense, the Robins and Guze criteria for validity1 have not been accomplished. The conclusion from all this is that the current set of diagnostic constructs cannot be considered true phenotypes that in any way match underlying genetic and pathophysiologic findings: “As it turns out, most genetic findings and neural circuit maps appear either to link to many different currently recognized syndromes or to distinct subgroups within syndromes.”2
This stalemate with the DSM categories has led to an entirely different approach to organizing research in psychopathology. In dramatic contrast to the DSM-III/DSM-IV approaches (begin top-down, with reliably established, descriptive diagnostic constructs and then search for the underlying genetic and pathophysiologic foundations), the new approach initiated by the NIMH—called the NIMH Research Domain Criteria (RDoC) project2,3 —starts bottom-up, with smaller, more fine-grained units of behavior or function (called “constructs”) that have been shown to be associated with disruptions of neural circuitry. These constructs are provisionally grouped into 5 larger “Domains.” The domains and constructs are placed in rows in a matrix, with the columns then representing the various ways in which the constructs can be studied: the columns currently listed are genes, molecules, cells, circuits, behavior, and self-reports. In this way any construct can be studied from a variety of perspectives, and the constructs can be studied against one another.
Two points are worth mentioning about the RDoC project. First, the RDoC constructs are not expected to match up with current DSM categories (and will crisscross through them), but are expected to play a significant role in future nosologies. As the NIMH team writes, “The NIMH is launching the RdoC project to create a framework for research on pathophysiology, especially for genomics and neuroscience, which ultimately will inform future classification schemes”4, p 748 Second, despite the matrix columns for behavior and self-report, the project treats psychiatric disorders as brain disorders. To quote the same authors: “First, the RDoC framework conceptualizes mental illnesses as brain disorders.”4, p 749 The project is thus fully in the spirit of the biological impetus that drove DSM-III.
Where does the RDoC project leave DSM-5? In a word: in an odd place. On the one hand, the architects of DSM-5 have been quite aware of the failures to match DSM-IV constructs with genetic and neuroscientific findings.5-8 On the other hand, both DSM-5 and the RDoC project place major importance on dimensional measures. Writing about the evolution of DSM-5 in 2009, Regier and colleagues wrote that “Thus, we have decided that one, if not the major, difference between DSM-IV and DSM-V will be the more prominent use of dimensional measures in DSM-V.6,p 649 And Strategy 1.4 of the NIMH Strategic Plan is: “Develop, for research purposes, new ways of classifying mental disorders based on dimensions of observable behavior and neurobiological measures.”3
The coincidence of dimensionality in both the RDoC project and DSM-5 does not reflect an influence of the former on the latter. The difference between dimensions in the RDoC project and dimensions in DSM-5 is that, while the former are part of an effort to further research into constructs with known disruptions in neural circuitry, the latter are more of a fishing expedition to increase the validity of the existing manual (eg, by adding cross-cutting dimensional measures of anxiety and depression to the existing categories). The dimensional measures proposed for DSM-5 are, we might say, an effort to produce a “RDoC-lite.”
In view of the fact that significant scientific progress in understanding mental disorders will have to wait for the results of the RDoC project or of similar work in genomics and neural circuitry,9 it is not hard to support the conservative attitude toward change in DSM-5, especially with respect to the proposed dimensional measures, espoused by Allen Frances and others.10-11
References
1. Robins E, Guze SB. Establishment of diagnostic validity in psychiatric illness: its application to schizophrenia. Am J Psychiatry. 1970;126:983-987.
2. National Institute of Mental Health Research Domain Criteria Project (RDoC). http://www.nimh.nih.gov/research-funding/nimh-research-domain-criteria. Accessed April 13, 2011.
3. National Institute of Mental Health Strategic Plan. http://www.nimh.nih.gov/about/strategic-planning-reports/index.shtml. Accessed April 13, 2011.
4. 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.
5. Kupfer DJ, First MB, Regier DA, eds. A Research Agenda for DSM-V. Arlington, VA: American Psychiatric Association Press; 2002.
6. Regier DA, Narrow WE, Kuhl EA, Kupfer DJ. The conceptual development of DSM-V. Am J Psychiatry. 2009;166:645-650.
7. Hyman SE. Can neuroscience be integrated into the DSM-V? Nat Rev Neurosci. 2007;8:725-732.
8. Regier DA, Narrow WE, Kuhl EA, Kupfer DJ, eds. The Conceptual Evolution of DSM-5. Arlington, VA: American Psychiatric Publishing; 2011.
9. Akil H, Brenner S, Kandel E, et al. Medicine. The future of psychiatric research: genomes and neural circuits. Science. 2010;327:1580-1581.
10. Frances A. DSM in philosophyland: curiouser and curiouser. Bulletin of the Association for the Advancement of Philosophy and Psychiatry. http://alien.dowling.edu/~cperring/aapp/bulletin.htm. Accessed April 13, 2011.
11. Phillips J. DSM-5 is a many-dimensioned thing. Psychiatric Times. http://www.psychiatrictimes.com/blog/dsm-5/content/article/10168/1696725. Accessed April 13, 2011.
