There’s no such thing as “mild depression”

Forget the categories.
Forget the categories.
Image: Unsplash/Elisabetta Foco
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In his memoir, Noonday Demon: An Atlas of Depression, writer Andrew Solomon makes a critical point about two models of depression, the categorical and dimensional.

The first sees depression “as an illness totally separate from other emotions, much as a stomach virus is totally different from acid indigestion,” he writes. The second says that depression is on “a continuum with sadness, and represents an extreme version of something everyone has felt and known.”

The models seem to contradict the other, but Solomon argues “both are true.”

You go along the gradual path or the sudden trigger of emotion and then you get to a place that is genuinely different. It takes time for a rusting iron-framed building to collapse, but the rust is ceaselessly powdering the solid, thinning it, eviscerating it.

Anyone who has lived near or with depression will understand the paradox he proposes on a visceral level. They may also have noticed, however, that the book US doctors use to diagnose mental disorders, the Diagnostic and Statistical Manual of Mental Disorders (DSM), has no room for such complexity. It relies on categories and binaries. More troubling, its categories are defined with what many experts say are arbitrary measures.

The checklist approach

According to the DSM-5, the manual’s latest edition, a person who suffers from a major depressive disorder must have a total of five out of nine symptoms from a checklist that includes problems such as insomnia or excessive sleepiness, and loss of appetite or overeating. One of the five symptoms must be either: experiencing a depressed mood or the loss of interest or pleasure in daily activities. And the symptoms need to have persisted for a two-week period.

If a patient reports only four of nine signs of depressive disorder, they should not receive the diagnosis—not according to the DSM, often called “the bible of psychiatry,” which in 1980 essentially carved in stone the parameters that define depression. But of course, a person with four hallmarks of the disturbance might actually be quite seriously depressed, and may need treatment.

“As the arbitrariness makes obvious, we can’t assert that someone with four out of nine symptoms has a different illness than someone with the magical five out of nine symptoms,” says Jonathan Stewart, a Professor of Clinical Psychiatry at Columbia University. In fact, he adds, there’s pretty good data that suggests it is the same illness.

The other odd feature of this diagnostic approach is that a cluster of traits that assigns one patient the diagnosis of “depressive disorder” could differ greatly from the selection of traits that gave someone else the exact same label. In fact, two depressed people could have only one feature of the diagnosis in common.

Stewart once calculated how many permutations of symptoms would lead to a diagnosis of clinical depression and found it was more than 3,000. (Many of the nine include two possibilities—for instance, “feelings of worthlessness and/or excessive guilt.”)

He believes that what we call depression encompasses an unknown number of disease entities—that it’s simply not a homogeneous ailment. What’s more, what we’ve known as “mild” or “moderate” or “major” depression are not separate disorders.

Here’s a quick history of how these thresholds came to be:

First issued in 1952 by the American Psychiatric Association (APA), the DSM initially defined depression and other psychological disorders leaving much room for interpretation. This came to be seen as problematic, especially for medical research. As Stewart points out, how could scientists say they’re researching treatments for “depression,” if the cluster of traits of the subjects in San Diego vary wildly from those of the subjects in New York?

In the late 1960s, a group of psychiatrists at Washington University in St Louis came together to create a more medical model for the illnesses, looking for the biological signs of the conditions. Their resulting research, which became known as  “the Feighner criteria,” after the name of the first author on a landmark paper published in 1972, essentially established the symptoms of depression we know today. The DSM-III committee, led by the efforts of noted psychiatrist Robert Spitzer, largely adopted the Feighner criteria, enforcing quantitative standards for clinical diagnoses and research.

The DSM-III was a major innovation, says Stewart. Researchers could finally speak the same language. It’s also been linked to “a mushrooming” of diagnoses of depression through the 1980s, he says, and a huge uptick in prescriptions, which he sees as a good thing—a boon to public health. However, the DSM’s method of establishing the traits and thresholds for a disorder by committee has also been questioned; as have many of its decisions about what was abnormal behavior.

So why did the committee choose five out of nine signs of trouble, and not seven, eight, or nine out of nine, to signal depression? Stewart proposes: “I don’t think they had any scientific basis for drawing the line, but they felt it had to be drawn somewhere,” and the threshold needed to be low enough that it would be possible to recruit study subjects efficiently. “They said, ‘If we make it nine out of nine, we’ll never get a study done,’” he suggests. “Those people exist, but they’re rare birds.’”

A new way to look at it

A consortium of 40 researchers have just unveiled a new system for diagnosing psychological illnesses, as a reaction to the DSM’s rigid binaries and random cut-offs. The Hierarchical Taxonomy Of Psychopathology, or HiTOP, was officially unveiled online last month after more than 20 years of discussion and development among researchers, led by scientists at Stony Brook University and University of Minnesota, and including members from University of Notre Dame, Duke University and King’s College London, the Broad Institute at Harvard University and MIT, and Purdue University, among others.

It builds an individual’s profile from the bottom up, and places mental disorders along a spectrum, and it also factors in an analysis of features that tend to co-exist. Miri Forbes, Postdoctoral Fellow at the University of Minnesota, who is part of this group, told Quartz that the HiTOP framework is about addressing the truth of human experience. “It’s not a yes or no structure. People are so much more messy and complicated than that.”

Roman Kotov, the psychologist and associate professor at Stony Brook University who spearheaded the efforts to launch HiTOP, says it doesn’t yet have the scope and depth to replace the DSM, but that it might get there, with time and more funding. Even if it remains an adjunct tool to help define psychological diagnoses with dimensional measures, which studies have shown to be more reliable than a categorical approach, that would be fine with him. “This is about moving the science forward,” he told Quartz, “not selling books.”

Recent editions of the DSM have taken a slightly wider view of depression, creating categories that recognize individuals who fall below the five-symptom threshold but whose issues persist over a two-year period. Still, “depressive disorder” remains a nebulous term.

Yes, there is some categorical distinction between the depression many manage to endure on a daily basis and the complete collapse of major depression, as Solomon writes. And the checklist approach that the DSM takes has some utility, as “a double-edged sword,” says Stewart, making it obvious to those who need treatment that they can’t ignore their illness, and, in theory, meaning that cases that go undiagnosed are not the most severe.

But what people need to understand, he adds, is that even though there’s some importance to the magical five out of nine number, a person who falls below that threshold may still be struggling with a major malaise.