A Blood Test for Depression

Post image for A Blood Test for Depression

Connection found between a brain network implicated in depression and levels of serotonin in the bloodstream.

Scientists have claimed that it is possible to detect the signs of depression using a blood test, despite many believing it is impossible.

The claim comes from researchers at the Medical University of Vienna, who have found a close relationship between a brain network implicated in depression and levels of serotonin in the bloodstream (Scharinger et al., 2014).

The study’s lead author, Lukas Pezawas said:

“This is the first study that has been able to predict the activity of a major depression network in the brain using a blood test.

While blood tests for mental illnesses have until recently been regarded as impossible, this study clearly shows that a blood test is possible in principle for diagnosing depression and could become reality in the not too distant future.”

A wandering mind

The network Pezawas is referring to is sometimes called the ‘default mode network': essentially it means the areas of the brain which kick into action when our minds are wandering.

One of the components of depression is excessive mind-wandering to negative thoughts and an inability to concentrate.

Interestingly, people with depression also tend to have problems suppressing activity in the brain’s default mode network.

The blood test that the team envisages would measure the level of serotonin in the blood.

Serotonin in the brain — sometimes known as the ‘happiness hormone’ — plays an important role in regulating the default mode network.

What the researchers have discovered is that serotonin function in the blood (not the brain) nevertheless predicts activity in the default mode network.

In other words: you can do a blood test on someone and it will tell you something about the function of a brain network which has been associated with depression.

Depression is about more than just serotonin

This study is fascinating and may eventually lead to a useful diagnostic tool, but it’s worth pointing out a few reservations:

  • Depression is about way more than just serotonin levels. If it were, the current batch of SSRI anti-depressant drugs, which target serotonin, would work much better than they do (which is: not that well).
  • Depression can’t be explained just by activity of the default mode network.
  • Depression is not like a switch, either ‘on’ or ‘off’, it’s a sliding scale. Thinking of it like a biological disease which you either have or don’t have is not helpful. Mainly because it’s not true.
  • If you want to find out if someone is depressed, just ask them. The answer may not be as clear and feel as scientific as a blood test, but it may be more useful.

Image credit: kygp

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About the author


Dr Jeremy Dean is a psychologist and the author of PsyBlog. His latest book is "Making Habits, Breaking Habits: How to Make Changes That Stick". You can follow PsyBlog by email, by RSS feed, on Twitter and Google+.

Published: 6 May 2014

Text: © All rights reserved.

Images: Creative Commons License