One of the most astonishing developments in psychiatry in the past year is the announcement of a potentially competing diagnostic system to the American Psychiatric Association's DSM-5 (Diagnostic and Statistical Manual, 5th edition) called RDoC (Research Domain Criteria). Although NIMH rightly insists that RDoC is exclusively a classification system devoted to research, the potential for RDoC to undermine the scientific credibility of DSM-5 and to conflict with DSM-5 in other ways persists. Until now the DSM system has served both clinical and research needs in psychiatry. DSM-5 presumably will continue to inform research. Disagreement between the two systems about research classification is easy to imagine. Carrying the apparent mantle of better science, RDoC may be the winner in any such disagreement.
The RDoC system begins with the recognition that the DSM system has little correspondence to underlying biological realities. For example, schizophrenia and bipolar disorder, two relatively discrete clinical DSM entities, often seem related to similar genes. Also, various discrete psychiatric illnesses seem to relate to the same nuclei and neural tracts in the brain. RDoC would attempt to understand and organize information about the functions of genetic mechanisms and the tracts of nerves in the brain. DSM is created to correspond to the clinical descriptions of psychiatric disorders rather than their underlying biological processes. When underlying biological processes have been sought for DSM diagnoses, they often could not be identified. As has been often said, the brain did not read the DSM.
According to Thomas Insel, MD, the Director of NIMH, and colleagues, the RDoC rests on three assumptions: 1)Mental illness arises from difficulties in neural circuits in the brain; 2)The difficulties in these brain circuits can be studied with available technology or technology soon to be developed, and 3) study of brain circuits and genetics will enhance clinical care by leading to identifiable dysfunctions.
The RDoc contains both pessimistic and optimistic stances toward the current state of knowledge in mental health research. A pessimistic stance may be found in the belief that we know very little about the processes underlying mental illness; an optimistic stance is found in the suggestion that we now have the technology and the resources to gain this knowledge. RDoC provides a research framework to begin to identify what we know and what we don't know. For example, it has long been believed that schizophrenia was related to excessive amounts of a neurochemical called dopamine. After many decades this does not seem to be true. RDoC provides a framework to organize evidence in favor of and against excessive dopamine as a dysfunction related to schizophrenia.
The RDoC relies upon the latest technological developments in neuroimaging (x-ray technology of the brain and genomics (genetics). Also the RDoC focuses on developmental aspects of psychopathology. Development can be thought of as another axis of RDoC. RDoC is keenly interested in the study of the relationship between the brain and environment. The creators of RDoC believe that the system will eventually lead to clinical applications, but wish to be careful and thoughtful about applying the findings to patients.
This presentation of RDoC is greatly oversimplified and omits much. It does serves to point out that there is another classification of psychiatric illness. The classification may well elevate the level of scientific study. Patients, practitioners, and researchers all deeply wish to place psychiatry on a firmer scientific basis. This scheme along with current technology seems to hold promise.
For more details about the RDoC system, consult the NIMH website: http://www.nimh.nih.gov/research-funding/nimh-research-domain-criteria-rdoc.shtml.
From a clinical perspective, there are several potential difficulties. One is that the system emphasizes a dimensional approach to symptoms rather than the DSM categorical approach. For example under the domain for Negative Valence and aggression, various degrees of aggression could be recorded and studied. A problem develops when this dimensional research approach is prematurely translated into the clinical arena. This is not a mere theoretical possibility, but the crossing of a boundary between research and practice that has already begun to take place. At the 2011 annual meeting of the American Psychiatric Association, I had the pleasure of hearing several excellent presentations on RDoC. During the discussion of these presentations one practitioner volunteered that he no longer treated patients according to their DSM diagnoses, but only on the basis of their symptoms. The panel of speakers politely murmured agreement with his approach suggesting that the dimensional quality of RDoC supported such a tactic. This seems to me to be an premature generalization from a complex research idea into an oversimplified clinical approach to treatment. Anxiety is found in many psychiatric disorders. The clinician is still responsible for organizing additional symptoms the patient has with the anxiety symptom into a coherent DSM diagnosis. Is this the anxiety of an anxiety disorder, the anxiety of a depressive episode, the anxiety of schizophrenia? There is no warrant at this time to treat the symptom of anxiety in isolation from other symptoms the patient may have.
Premature translation of child bipolar disorder from a research exploration into the clinical arena led to many of the problems surrounding so-called pediatric bipolar disorder. As a research idea in the late 1990's, pediatric bipolar disorder had legitimate appeal. The possibility that bipolar disorder might manifest itself in younger age groups seemed a reasonable research hypothesis. It was the intense precipitous translation of a research hypothesis into the clinical truisms and the pop culture embrace of the idea that in part led to the unwarranted increase in rates of diagnosis and treatment of a misdiagnosed illness. Much of the misdiagnosis of bipolar disorder in children stemmed from a spectrum approach to making a diagnosis rather than the categorical approach of DSM-IV. The crucial illustration of this is the use of varying degrees of anger in children to make a diagnosis of bipolar disorder. Severely angry children were often diagnosed with bipolar disorder based on the severity of their anger. This approach to the diagnosis had little in common with the DSM IV-criteria for the diagnosis of bipolar disorder. The misuse of this spectrum approach led to the misdiagnosis of many thousands of children. The dimensional or spectrum approach of RDoC should not be applied to clinical work at this time.
The RDoC appears at an awkward time for DSM-5. DSM-5 is struggling for acceptance among the general public, and the appearance of another "more scientific" approach, no matter how welcome or needed, will not help.