An inaugural publication from an international consortium of psychologists and psychiatrists offers a new approach to diagnosing mental disorders. The Hierarchical Taxonomy of Psychopathology (HiTOP) -- introduced by Dr. Roman Kotov and colleagues (Online First) in the Journal of Abnormal Psychology -- is a new, dimensional classification system of a wide range of psychiatric problems that was developed to reflect the state-of-the art scientific evidence.
Diagnosis is important because it defines groups of patients who will receive treatment and public assistance. It is used by drug companies for development of new medications and guides research efforts overall.
Recent years have seen clashes over psychiatric diagnosis. The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, or DSM-5, was published in 2013 and immediately divided medical opinion. DSM-5 is a guidebook by the American Psychiatric Association on how to diagnose mental disorders. It has many critics, including the National Institute of Mental Health (NIMH), which in response produced an alternative model to guide research efforts. However, this approach has also been controversial, as it focuses heavily on neurobiology and much less on investigating issues that are important for everyday psychiatric care, such as symptoms and illness course.
The HiTOP system has been articulated to address the limitations currently plaguing psychiatry. First, the system proposes to view mental health as a spectrum. Mental health problems are difficult to put into categories, as they lie on the continuum between pathology and normality, much like weight and blood pressure. Applying an artificial boundary to distinguish what is a healthy behavior versus mental illness results in unstable diagnoses, as one symptom can change the diagnosis from present to absent. It also leaves a large group of people with symptoms that do not reach the threshold untreated, although they suffer significant impairment.
Second, the HiTOP system simplifies the classification. Different DSM-5 diagnoses co-occur with surprisingly frequency, with most patients labelled with more than one disorder at the same time. Furthermore, many diagnostic categories are so complex that often two patients with the same diagnosis do not share a single symptom in common. The HiTOP solution to these fundamental problems is to classify psychopathology dimensions at multiple levels of hierarchy. This allows doctors and researchers to focus on finer symptom in detail, or assess broader problems, as necessary.
For example, social anxiety disorder is a category in the DSM-5, while the HiTOP model describes it as a graded dimension, ranging from people who experience mild discomfort in a few social situations (e.g., when giving a talk in front of a large audience) to those who are extremely fearful in most situations. The HiTOP system recognizes that clinical levels of social anxiety are not fundamentally different from regular social discomfort. It also does not treat social anxiety as a single problem but instead recognizes important differences between interpersonal fears (e.g., meeting new people) and performance fears (e.g., performing in front of an audience). Moreover, people with social anxiety are prone to other anxieties and depression, and the HiTOP model describes a broad spectrum called internalizing that captures overall severity of such problems. Thus, while the narrow level of hierarchy can provide good targets for symptom-specific treatments (e.g., public speaking), the higher level of hierarchy is helpful when designing comprehensive treatment packages and developing public health policy.
Finally, unlike DSM-5, the HiTOP project adheres to the most up to date scientific evidence, rather than relying on expert opinion. HiTOP effectively summarizes information on shared genetic vulnerabilities, environmental risk factors, and neurobiological abnormalities. For example, it is becoming increasingly clear that genetic risk factors do not adhere to diagnostic categories, instead genetic research identifies broad genetic risk factors that cut across diagnoses and largely line-up with the HiTOP dimensions.
Kotov, R., Krueger, R. F., Watson, D., Achenbach, T. M., Althoff, R. R., Bagby, R. M., Brown, T. A., Carpenter, W. T., Caspi, A., Clark, L. A., Eaton, N. R., Forbes, M. K., Forbush, K. T., Goldberg, D., Hasin, D., Hyman, S. E., Ivanova, M. Y., Lynam, D. R., Markon, K., Miller, J. D., Moffitt, T. E., Morey, L. C., Mullins-Sweatt, S. N., Ormel, J., Patrick, C. J., Regier, D. A., Rescorla, L., Ruggero, C. J., Samuel, D. B., Sellbom, M., Simms, L. J., Skodol, A. E., Slade, T., South, S. C., Tackett, J. L., Waldman, I. D., Waszczuk, M. A., Widiger, T. A., Wright, A. G. C., & Zimmerman, M. (2017, March 23). The Hierarchical Taxonomy of Psychopathology (HiTOP): A Dimensional Alternative to Traditional Nosologies. Journal of Abnormal Psychology. Advance online publication. http://dx.
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