New Study Suggests Blood Tests Can Identify Depression

Blood tests designed to detect a wide variety of ailments are old news—getting “bloodwork done” is a standard part of going to the doctor to get symptoms checked out. But a new study suggests that blood testing might be crossing over into mental-health territory. Soon, it might be able to detect depression.

The study, published yesterday in the journal Translational Psychiatry, unveiled a test that researchers say determined the presence or absence of early-onset major depressive disorder, or MDD, in a group of adolescent experimental subjects.

MDD, which affects adolescents and young adults, is caused by both genetic and environmental factors, and each leaves different sorts of hints, or markers, in the bloodstream. By examining animal models of the disease from both these angles, the team of researchers—led by Eva Redei, a professor of psychiatry and behavioral sciences at the Northwestern University Feinberg School of Medicine—was able to determine which markers would be most likely to show up in humans with MDD, and to narrow it down to a set that they could use to test for the disease. When the researchers applied the test to a group of adolescents—14 with the disease and a control group of 14 without it—they found that it successfully distinguished those with the disease from those without it.

“The idea is that a blood test can be developed—and this was the first proof—to diagnose depression,” Redei told The Daily Beast. “Just like any other laboratory test, there is a normal range, and then you’re tested and you’re either in the normal range or out of it.”

Redei and her colleagues described the results as “pilot data,” and at least one other researcher wasn’t yet ready to celebrate. Alexander Niculescu, a professor of psychiatry at the Indiana University School of Medicine who has conducted similar research on how mental disorders connect to blood markers, said he wasn’t convinced Redei and her colleagues had done enough to prove that their results were more than statistical noise. But he definitely saw promise in their strategy.

“I think their results are not solid,” Niculescu said. “I think the approach overall that they are taking is solid, but I’m biased because we’ve taken that same approach in a more comprehensive fashion.”

In an email, Redei elaborated on how her team’s results could be broadened to include more subjects.

“There is nothing general about the test,” Redei said. “[O]ur paper suggests that this particular test is very likely to work in a larger population of teens as well. The next step is indeed a larger population of youth, with depression more varied in their severity and comorbidity with other illness.”

Such a test would be a useful addition to clinicians’ toolkits, especially since, as Redei pointed out, depression can slow subjects’ thinking and cause them to become withdrawn, making it more difficult to interview them. “You’re basically relying in some of your diagnoses on a broken arm being able to lift a weight,” she said. “This field truly cries out for objective measures.”

But there’s a potentially dangerous other side to this sort of testing, said Michele Goodwin, a law professor and bioethicist at the University of Minnesota. If diagnosing depression shifts from a mostly interview-based process to a more quantitative, blood-based one, she said, the potential for overdiagnosis—and overmedication—will grow, especially in vulnerable populations.

This is especially troubling given the United States’ track record in this area, Goodwin said.

“It has to be understood within the context of our culture,” she said. “In a culture that’s so quick to medicate on everything, including on cases where it might appear quite problematic that we would choose medicine over other alternatives, then there might be cause for some concern.”

Goodwin cited the example of K-12 schooling in the United States, where children are often routed into special-ed programs based not on specific learning disabilities, but on behavioral problems. The system overwhelmingly lumps poor kids, and particularly poor minority kids, into that category. And from there they are often put on medication at a very young age.

“We’re a nation of shortcuts,” Goodwin said. “So however we think about what ideally we would want to do, the reality is that we are in a space of doing something different.”

Redei doesn’t see this as a problem—at least, not yet. Asked via email whether there was a risk of children being put on antidepression medication as a result of a single test taken at a time when they were just in a funk—say, over a breakup—she responded, “Some of these markers are ‘fast’ responding ... and others are slow. So, obviously a ‘funk’ would mobilize the fast ones but not the slow ones.”

Nor was she concerned about an over-reliance on blood tests at the expense of other, more clinical assessment methods. “I don’t think that this will replace psychiatric interviews,” Redei said. “It definitely would add to [them] in a way that any other laboratory test informs the physician of all kinds of things.”

Whatever the merits of tests for depression and similar ailments, two things are certain: there’s a market for them, and they would change how we view mental disorders. According to Niculescu, two companies are already marketing blood tests for depression and schizophrenia—“prematurely, in my scientific opinion,” he wrote in an email to The Daily Beast.

But Niculescu is hopeful about these sorts of tests overall. “I think that when things are more quantitative, psychiatry will be on par with the other medical specialties, and then you can follow more closely how people respond to treatment,” he said.

“I just don’t want premature hype and hope to create a backlash.”