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Different Approaches to Understanding and Classifying Mental Disorders

An in-depth look at the DSM, the ICD, and the NIMH’s RDoC

Science Update

Research in a wide range of disciplines supports the idea that mental disorders result from the complex interplay of biological, developmental, social, and environmental processes; however, the more we learn about mental disorders, the more we realize there are still gaps in our understanding of how best to classify, diagnose, and treat them.

In a new report, authors representing a range of research centers and institutions discuss challenges in the conceptualization and classification of mental disorders and detail how each of three existing approaches—the International Classification of Diseases (ICD), the Diagnostic and Statistical Manual of Mental Disorders (DSM), and the National Institute of Mental Health (NIMH)’s Research Domain Criteria (RDoC)—handles these issues.

The DSM and ICD serve as guides for the diagnosis of mental disorders. These two approaches use a category-based classification system, meaning specific conditions are grouped within broader categories of disorder. For example, the condition “separation anxiety disorder” appears within the broader category of “anxiety disorders.” Each condition within a category is defined by a set of criteria that must be met for diagnosis to occur.  

While the category-based structure used by the DSM and ICD helps simplify and standardize the diagnostic process for clinicians, these systems often result in comorbid diagnoses (i.e., when people are diagnosed with multiple disorders at one time), and are sometimes criticized for the seemingly arbitrary boundaries they set between disorders and nondisorders.

According to author Dr. Bruce Cuthbert, Ph.D., of the NIMH RDoC Unit, these issues result, in part, from the fact that the structure of current diagnostic systems was “developed several decades ago, well before systematic knowledge of specific cognitive functions or brain systems was available,” and as such “do not reflect much of what we now understand about the processes related to mental disorders.”

According to Dr. Cuthbert, “we now understand that the categories are not specific diseases (like Lyme’s Disease or influenza) but rather are broad syndromes – loose collections of symptoms that tend to occur together to some extent, and involve dysregulation in multiple domains."

The third approach detailed in this report, RDoC, represents a different way to conceptualize mental disorders. RDoC is not meant to serve as a diagnostic guide, but instead as a research framework that aims to deepen understanding of the biological, social, developmental, and environmental factors involved with psychological functioning in general. As a result, RDoC is not bound by specific categories or classifications of disorders or by thresholds of diagnosis.

The RDoC framework is conceived as a matrix focusing on five major systems, or domains, that influence human functioning (e.g., negative valence systems, cognitive systems). Contained within each domain are behavioral elements, or constructs, that result from these systems. Constructs are studied along a span of functioning from normal to abnormal with the understanding that each is situated in, and affected by, environmental and neurodevelopmental contexts. Measurement of constructs can occur using several different methods, or units of analysis, which include genetic, physiological, behavioral, and self-report assessments.

“RDoC is an attempt to generate data that will help provide more precise diagnosis and treatment, and – by understanding the processes by which dysregulated functioning evolves over time – may lead to prevention and pre-emption of disorders,” says Dr. Cuthbert. RDoC, then, is not intended to replace current diagnostic systems, but to provide information that may eventually help improve the diagnosis and treatment of mental disorders.

The report, authored by Lee Anna Clark, Ph.D. (University of Notre Dame), Bruce Cuthbert, Ph.D. (NIMH Research Domain Criteria Unit), Roberto Lewis-Fernández, M.D. (Columbia University), William E. Narrow, M.D., M.P.H. (University of New Mexico School of Medicine), and Geoffrey M. Reed, Ph.D. (World Health Organization; Columbia University Medical Center), appears in the December 2017 issue of Psychological Science in the Public Interest.

In an accompanying commentary, Paul Appelbaum, M.D., of Columbia University praises the historical and conceptual analysis provided by the authors and expands upon some of the main themes discussed in this report: the role of science in revising current diagnostic frameworks, the incorporation of dimensional approaches into diagnostic systems, and reasons for differences among these approaches.

References

Clark, LA., Cuthbert, B., Lewis-Fernández, R., Narrow, W., Reed, G. (2017). Three approaches to understanding and classifying mental disorder: ICD-11, DSM-5, and the national institute of mental health’s research domain criteria (RDoC). Psychological Science in the Public Interest, 18 (2), 72-145. doi: 10.1177/1529100617727266

Appelbaum, P. (2017). Moving toward the future in the diagnosis of mental disorders. Psychological Science in the Public Interest, 18 (2), 67-71. doi: 10.1177/1529100617727267

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About the National Institute of Mental Health (NIMH): The mission of the NIMH is to transform the understanding and treatment of mental illnesses through basic and clinical research, paving the way for prevention, recovery and cure. For more information, visit the NIMH website.