Mental Health Diagnosis: How HiTOP is Changing the Rules

For decades, the traditional approach to mental health has relied on a rigid checklist, assigning patients a single category label like "depression" or "anxiety." But human experiences are rarely that neat.

At the University of Minnesota, Distinguished McKnight University Professor Robert F. Krueger is leading a global data-driven revolution to change that. As one of the world's most highly cited researchers in psychology, Krueger is a driving force behind the Hierarchical Taxonomy of Psychopathology. HiTOP, for short, is an innovative model that approaches mental health not as a rigid checklist, but as a fluid spectrum.

In honor of Mental Health Awareness Month, Professor Krueger shared insights into how this UMN-born research is moving past traditional labels to finally treat the "whole person."

The Spark of an Idea

Q: You have been recognized as one of the world’s most highly cited and influential researchers in psychology. Looking back at your career at the University of Minnesota, what initially drew you to studying the way we classify and diagnose mental illness?

Prof. Krueger: "My interest in the classification of mental illness traces back to my early experiences as both a clinician and researcher. The traditional approach... assumes that patients can be assigned to specific category labels in a way that should help facilitate effective intervention.

Yet, most of the people I saw in clinics and most of the data I worked with in research showed that patients do not fit neatly within single categories. Most patients had a mix of strengths and challenges that defied traditional categorical labels. So, I became interested in working on alternatives... that might have the potential to lead to better conceptualization of patients, which, in turn, could lead to more compelling research on the origins of mental illness."

The Lab Work Analogy: Moving from Checklists to Spectrums

Q: For readers who might not be familiar with clinical psychology frameworks, how would you explain HiTOP? If you had to use a relatable analogy, like a spectrum or a continuum, how does it shift how we think about mental health?

Prof. Krueger: "HiTOP stands for the 'Hierarchical Taxonomy of Psychopathology.' So it's a taxonomy, that is, a way of classifying the features of mental illness... and it's hierarchical.

Traditional classification systems for mental illness divide clinical conditions into what are intended to be relatively mutually exclusive categories. The idea is to perform a 'differential diagnosis' [where a clinician chooses a single, definitive diagnosis from hundreds of options] and decide which label best matches the patient's presentation. By contrast, a hierarchical approach acknowledges that this traditional approach doesn't fit the data on how mental illness actually presents.

When you model actual mental illness data, you find basically no evidence that the features of mental illness form discrete categories. Instead, the features form spectrums of continuous variation... To state that idea tangibly and practically, using the familiar examples of depression and anxiety, people don't appear in the clinic as being clinically depressed (or not) and clinically anxious (or not). Instead, a typical presentation involves a mix of depressive and anxious features...

Having to choose a specific category label and make a choice as a clinician... just doesn't work because real patients simply don't fit neatly into those types of categories. Instead, in a 'HiTOP approach', patients are characterized along dimensions that jointly capture features that tend to run together in nature. Think of it as a profile akin to when you get blood work back from the lab. You can think about critical levels on key indicators of health (e.g., your cholesterol level) but those levels vary continuously, with multiple ranges from 'doing ok' to 'somewhat concerning' to 'very concerning' for example. HiTOP is doing basically the same thing with the features of mental illness, organizing them into dimensions and creating a profile across those dimensions..."

A Minnesota Powerhouse: The Strength of Collaboration

Q: HiTOP is inherently collaborative, and you and Professor Colin DeYoung have built a powerhouse of research around it here at UMN. How has your collaboration helped accelerate the framework's global adoption?

Prof. Krueger: "Collaboration works well when the collaborators have complementary expertise along with a shared vision. The collaboration I've enjoyed with Colin has both of these features.

For example, Colin has more of a background in neuroscience and I have more of a background in genetics... Yet we both have the shared vision of trying to improve clinical conceptualization of mental illness, which, in turn, should help facilitate discovery in both genetics and neuroscience. And, long story short, the data emerging in both the neuroscience and genetics of mental illness correspond more closely to a HiTOP type of model than a traditional category type of model."

Treating the Whole Person, Not the Label

Q: At its core, your research aims to reduce the burden that mental health problems place on society. How does moving to a dimensional, spectrum-based system actually improve the lives and treatments of patients sitting in a clinic today?

Prof. Krueger: "Probably the most fundamental improvement is in being able to conceptualize patients in more nuanced and clinically accurate ways that better capture the nature of both their strengths and limitations. Many patients are understandably frustrated by traditional [diagnostic] category labels because their experiences don't fit well into specific categories and, moreover, their strengths get pushed to the wayside... In a HiTOP type of approach, the clinician can communicate with the patient about their profile of challenges and strengths, and tailor intervention strategies that go beyond a focus on a specific category label.

To pick an example, two patients could be similarly anxious and depressed but vary in terms of their tendency to be agreeable [meaning they have] the capacity to get along well with other people, including the clinician. With the agreeable person, that strength can be leveraged to intervene [by encouraging things like social engagement outside of therapy]. By contrast, the disagreeable person requires a different strategy, where challenges in being able to get along easily with others needs to be addressed as a potential factor in understanding their emotional distress. In short, in a HiTOP type of approach, you're looking at a person as a whole, vs. reducing them to a single category label that doesn't really capture their entire personality."

A Legacy of Academic Freedom at UMN

Q: How has being part of the University of Minnesota College of Liberal Arts community supported this groundbreaking work, and what is your hope for the future of mental health awareness and diagnosis over the next decade?

Prof. Krueger: "UMN has been my academic home for decades and it is difficult to imagine working anywhere else. Basically, as a faculty member in the College of Liberal Arts, I have access to a world-class set of facilities and resources that allow me to pursue the types of large-scale research projects I have been fortunate to undertake.

Moreover, the Department of Psychology has a long history of allowing faculty to think broadly and creatively and not be confined to traditional ideas of what psychological science can or should be. So, to pick a specific example, genetics has been a big focus of our department for many decades before I arrived, and so I was able to tap into that richer intellectual environment. Studying psychological individual differences from a genetically informed perspective is highly unique among psychology departments, and I was very fortunate to learn from and work with other faculty who appreciate the importance of not being bound by traditional disciplinary boundaries."