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Yet Again: A Blood Test for Depression? I’m Not Holding My Breath

Yet Again: A Blood Test for Depression? I'm Not Holding My BreathThe news articles are breathless. “Objective Blood Test Can Diagnose Depression,” “Blood Test Flags Depression, Predicts Treatment Response,” and “There’s A Blood Test That Can Diagnose Depression!”

Wow! That’s just darned amazing. You mean we can draw blood from a patient (in a lab, which is usually some place separate you have to go to than the doctor’s office for many in America), send it off for processing, and two weeks later, get a result to see if the person has depression?

Or, you can take an objective, scientific screening quiz — like this one — in about a minute or two and have an instant result. Which is more amazing again??

Deja vu is setting in… like we’ve covered this topic before. And, in fact, we have. Not just once, but more that a few times.

I couldn’t find a single news outlet that noted that this is not the first time researchers have “discovered” a blood test for depression (or one that could help us better understand treatment response). And yet, researchers have been publishing such studies for at least 5 years now:

Yup, there they are. I had read this story before… all the way back in 2009. So where’s this blood test all these researchers keep claiming is just around the corner?

But here’s the real problem…1 What happens if the blood test developed doesn’t detect 100 percent of people are depressed? What happens if it only can detect certain types of depression in a certain percentage of people??

Real Depression vs. What You Have

My fear is that there’d be two groups of people with depression if such blood tests actually ever do come to market: real depression (as determined by the blood test), and then “what you have,” which must be something else (or some lesser kind of depression) — because the blood test couldn’t detect it. You may think this is just a hypothetical concern, but trust me when I say that it won’t be.

Because general practitioners — the group that unfortunately is responsible for most depression diagnosis and treatment in America today — is medically trained. They’ve been trained to go by what the lab results tell them, in this case: “Depression test: positive” or “Depression test: negative.” If it comes back negative, they may not even know that the depression blood test they’re ordered can only detect depression in a subgroup of the population. The well-meaning physician may then negate the seriousness of your subjective experience.

They may, in short, tell you that you don’t have depression when you absolutely do. They may say you’re just making it up in your head because “the test came back negative.”

How will this help anyone?

Today, we have a battery of reliable, objective testing to determine the severity and diagnosis of depression. Most take just a few minutes for a professional to administer, and some can be self-administered (like the Beck Depression Inventory or self-screening measures like the ones we publish).

I’m all for a blood test that is 100 percent (or close to it) reliable and can detect all kinds of depression in nearly everyone it’s administered to. But to-date, we’ve had these tiny studies (28 patients, 32 patients, etc.) that have suggested their results can be made into a world-applicable depression blood test for everyone, everywhere.

We are nowhere close to such a test. And when it does become available, while it’ll be wonderful for those whose depression can be detected by it, I rue those whose depression the test can’t see or detect.


Read the full article: Blood Test Flags Depression, Predicts Treatment Response

Yet Again: A Blood Test for Depression? I’m Not Holding My Breath


  1. The one that, again, not a single news story covered. []

John M. Grohol, Psy.D.

Dr. John Grohol is the founder of Psych Central. He is a psychologist, author, researcher, and expert in mental health online, and has been writing about online behavior, mental health and psychology issues since 1995. Dr. Grohol has a Master's degree and doctorate in clinical psychology from Nova Southeastern University. Dr. Grohol sits on the editorial board of the journal Computers in Human Behavior and is a founding board member of the Society for Participatory Medicine. You can learn more about Dr. John Grohol here.

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APA Reference
Grohol, J. (2018). Yet Again: A Blood Test for Depression? I’m Not Holding My Breath. Psych Central. Retrieved on October 24, 2020, from
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Last updated: 8 Jul 2018 (Originally: 25 Sep 2014)
Last reviewed: By a member of our scientific advisory board on 8 Jul 2018
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