Remarkable Promise: A New Blood Test for Major Depressive Disorder
Once a year I sit down with my doctor for a physical. She runs through the usual exam, then sends me off for a round of additional tests. Back when I was younger, a little extra lab work covered it. These days the appointment comes with the added fun of a mammogram and a colonoscopy, all filed under "routine." A week or two later I'm back in her office learning that my cholesterol has crept up, or my hormones have drifted off course, or something else wants a prescription and a follow-up. I walk out thankful anyway. Without those tests I might never have known, and whatever was wrong would have kept quietly chipping away.
There's one thing she never screens for: depression. The handful of questions she does ask, about how I'm sleeping or eating, aren't especially reliable. A long list of other illnesses wear the same symptoms, so a depression diagnosis plus an antidepressant could leave me with nothing but another bottle of pills and side effects I'd rather skip. Or it could be exactly what I need. The trouble is there's no way to be sure.
Diagnosing depression today rests almost entirely on judgment calls. The symptoms doctors go on, low mood, tiredness, shifts in appetite, point in a hundred directions and belong to plenty of conditions that have nothing to do with depression. The whole process also depends on the patient describing what they feel and the physician reading that description correctly. People who are depressed tend to say too little or struggle to put it into words.
Major depressive disorder reaches about 6.7 percent of American adults in a given year, and that figure keeps rising. Roughly 12.5 percent of primary care patients are thought to have major depression, yet only about half of those get diagnosed. With the methods available now, reaching a diagnosis can take anywhere from two months to as long as forty, and every month of delay makes the condition harder to treat. A biologically grounded test, recently developed, could change both the speed and the accuracy of that diagnosis.
Scientists at Northwestern University have built the first blood test capable of diagnosing major depression in adults. It offers something the field has never had: an objective, lab-based result. The test works by reading the levels of nine RNA markers in the blood. RNA molecules act as messengers, translating the instructions coded in DNA and carrying them out.
Eva Redei, who created the test and teaches psychiatry and behavioral sciences at Northwestern's Feinberg School of Medicine, put it plainly. "This test brings mental health diagnosis into the 21st century and offers the first personalized medicine approach to people suffering from depression," she said. Redei is co-lead author of the study, published September 16, 2014, in Translational Psychiatry. She added that patients could now be diagnosed through a laboratory test the same way they're diagnosed with high blood pressure or high cholesterol.
Three of the nine markers behaved in an unexpected way. Their blood levels stayed different between depressed patients and non-depressed controls even after the depressed patients had recovered through therapy. That gap seems to flag a lasting vulnerability. "These three markers move us towards the ultimate goal of identifying predisposition to depression, even in the absence of a current depressive episode," Redei said.
The test also tracked something therapy itself had never left a physical trace of. After 18 weeks of cognitive behavioral therapy, patients who were no longer depressed showed measurable changes in their markers: blood-based proof that the therapy had worked. Redei noted this distinction might one day predict who will respond to that kind of treatment before they start it.
David Mohr, the study's other lead author, directs the Center for Behavioral Intervention Technologies at Feinberg and teaches preventive medicine there. He drew a sharp comparison. "Mental health has been where medicine was 100 years ago when physicians diagnosed illnesses or disorders based on symptoms," he said. "This study brings us much closer to having laboratory tests that can be used in diagnosis and treatment selection."
Mohr went further on why targeting matters. Drug therapy helps some people and not others; psychotherapy does the same. Combining the two tends to beat either one alone, but he suspects that's partly because combining them amounts to a scattershot guess. A blood test, he argued, would let clinicians aim treatment at the individual instead. For patients prone to relapse, closer monitoring becomes possible. "They can consider a maintenance dose of antidepressants or continued psychotherapy to diminish the severity of a future episode or prolong the intervals between episodes," he said.
For patients and the doctors who see them, this is encouraging. A test that can name the illness, point toward a treatment and gauge the response stands to raise the success rate of any depression diagnosis. The hope is that guesswork and the errors that come with it will fade, and that mental health finally joins the rest of medicine in the 21st century. Someday a routine blood draw may steer accurate treatment for the mind as readily as it does for the body.
A reader's reflection follows. There's a worn-out line in our medicine-savvy culture: "There's a pill for that." At least one of my former physicians was fluent in that style of care. The saying holds up uncomfortably well. If there isn't a pill or a cream, there's almost certainly a test. For now I'll leave aside what I think about the entanglement of doctors and drug companies.
Consider HIV, the virus behind AIDS. Despite the publicity, the funding and the decades of research poured into a cure or even a vaccine, none exists as I write this. We've come a very long way from the 1980s and early 1990s, yet what we have is a test and some experimental treatments, not a cure.
When I show up with vague symptoms, the usual result is a prescription of some kind, topical, oral or injected. The diagnosis may ride on a biopsy, or blood, urine, skin or spinal work, or it may not. Often nobody looks past the range of numbers a test spits back. If my numbers sit on the borderline, I might get labeled with the "XYZ" disease, or I might not.
This is where I've irritated a few physicians. I've made the case that practicing medicine today is a refined form of gambling. A doctor meets a case, sometimes without ever really meeting the person attached to it, and ventures a diagnosis. Then come the referrals and more tests. The frequent outcome is a new medication piled onto an already crowded regimen. "Go ahead and start this and we'll see how it goes for a few weeks or months" has to be among the most common sentences spoken in an exam room.
I'm not naive. Medical care costs a fortune, and most insurers won't pay for the treatment most of us genuinely need. Still, I resent being treated like a fool for expecting real care across every part of who I am. The physical, emotional, mental and spiritual troubles that wear on me and on everyone else deserve the best available treatment, not a wager dressed up as a test.
Source: Northwestern University. (2014, September 17). First blood test to diagnose depression in adults. ScienceDaily. Retrieved December 10, 2014 from www.sciencedaily.com/releases/2014/09/140917121229.htm