Saliva Test May Predict Depression In Teen Boys

Feb 18, 2014

Researchers at the University of Cambridge in England have developed a saliva test for teenage boys with mild symptoms of depression that researchers say could help identify those who will later develop major depression. Currently, there is no biological test that detects depression.

Joe Herbert is one of the study authors and joins Here & Now’s Robin Young to discuss the research.


  • Joe Herbert, professor in the Department of Clinical Neurosciences at the University of Cambridge in England.
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Depression affects one in six people at some point in their lives. What if there was a way to find out when it starts and hopes of addressing it? Well, researchers at the University of Cambridge in England say they've developed what might be the first biological test to do just that. It's a saliva test for teenage boys with mild symptoms of depression. But researchers say it can help identify which of the teens might later develop full-blown clinical depression.

Professor Joe Herbert led the research. He joins us from the University of Cambridge. Professor Herbert, welcome.

JOE HERBERT: Thank you very much.

CHAKRABARTI: And can you start with which boys you're talking about? What are mild symptoms of depression that might lead to this test?

HERBERT: Well, depression is a kind of gradual thing. And there are now guidelines for separating people with minor depressive symptoms, you know, so a bit miserable but not really depressed enough for their lives to be affected in a serious way. That is what we called depressive symptoms. And - but there's a quite a jump between that situation and one where you get full major depression, which in an adolescent boy is going to have major effects on his life, like his friendships or his education and his, really, prospects.

CHAKRABARTI: Yeah. Well, I mean, just to - as people are thinking about their own children, so to somebody who's just really low and low key and maybe doesn't want to go out and play as supposed to someone who really is terribly crippled by depression, you tested more than 18,000, is it, teenagers, measured the level of the...

HERBERT: No, 1,700.

Oh, sorry, 1,700. Really bit of an extra zero there - and measured the level of the stress hormone cortisol in their saliva, what did you find?

When you measure hormones in the morning, cortisol has a big rhythm, so it's a high in the morning and low in the evening in everybody. But the height of the morning varies between people. And when you measure in a lot of boys like this, you find there's a great variation. Now, when we separated those who had a high level and together with that a fairly high score on this depressive scale, which didn't measure clear depression - it measured a depression as it were in the normal range - we find that this predicted to a very large degree the boys who will come depressed in the next three or four years. In fact, 25 percent of them became depressed.

CHAKRABARTI: So a higher rate of the stress hormone cortisol, which has - occurs naturally in the body...

HERBERT: That's right.

CHAKRABARTI: ...meant, or seemed to turn out that those young boys, three or so years later, had a more severe form of depression.

HERBERT: That's right. We've learned for quite a long time that cortisol, which, by the way, is an essential hormone; you needed to be alive, we know very well that that's become disregulated in depression. We also know that it becomes disregulated sometimes before depression. This was a fairly - an effect which was detectable often particularly large. When we add it to the symptoms of depression, it then becomes much larger. If they're together, the two are a much predictor than either alone.

CHAKRABARTI: But how about testing on teenage girls, was it the same?

HERBERT: It wasn't the same. The cortisol had no effect for just depression symptoms. So the males or the females, boys and girls, were similar in that depressive symptoms, particularly their risks for getting depressed. But for boys, cortisol added something, whereas girls didn't. Now, that doesn't mean that cortisol isn't active in girls, because you need to know that girls naturally have higher levels of cortisol than boys. So we wonder whether they have already exceeded the threshold, if you like, which would make them a risk for depression. All they need now is depression - is the symptoms of mild depression to add to that. But I must emphasize that, you know, a conjecture.


HERBERT: You need to analyze more data on that.

CHAKRABARTI: Yeah. But still a provocative thought. Well - but so what is - what you have found, tell doctors. Where do you think this should go?

HERBERT: Well, when you have a predictor, which is as powerful as this, there are several ways you can go. One, of course, you can develop a screening test. And it's as important to monitor the mental health of adolescence as it is of physical health, example, their fitness. And you can use these tests to do exactly that. And the important thing to bear is that you can pick out boys and maybe probably girls, actually, who are at high risk of depression and keep an eye on them, for two reasons. First of all, when they do get depressed, they get early and prompt treatment. And that makes a big difference to the outcome. And secondly, we do know that even in an advance country like yours and indeed mine, a large proportion of depressed adolescents are never diagnosed. They never get near a doctor. And that's bad news for them because, of course, they don't get treatment.


So let's say there is a simple test that's developed based on your research and there's a saliva test of young boys in particular and it's found that they have high cortisol rates in addition to the symptoms that they have of depression, could you then say, look, this is a young kid who maybe shouldn't be told to worry as much about a test that's keeping him up till one in the morning? In other words, are the high stress rates because of stress?

HERBERT: Though they say stressed, there are a lot of ways a cortisol can be high. Stress is one of them, and you can say, look into that. If there has, for example, high levels of anxiety, you could reduce that by various ways and see if you can reduce cortisol. But yes, the other point I was going to make is that when you find these predictors of an illness, then of course, it may give you some idea of what's causing the illness or at least these can be some of the factors causing it.

And that means that if you can modify these factors, for example, you can reduce the depression symptoms or reduce levels of cortisol, you might be able to quite markedly reduce the risk of depression. And because depression is such a common illness in young people, I say devastating, even if you only halved it, or less than that, you have a - quite a dramatic effect.

YOUNG: But again, just to - I think you were beginning to say, the high stress levels in - the high cortisol levels might not necessarily be tangibly stress related. There might be another reason, and there are things you can do to lower it.

HERBERT: That's quite right. There a lot of reasons why levels of cortisol can be high, apart from current stress. For example, you can have particular genes which raise your cortisol. Or another way is that children who have a history of poor parenting, particularly mothers, for example, who've had depression themselves after childbirth and therefore haven't been able to give their children the care they otherwise would, these children can have high levels of cortisol, even 10 or 15 years later. So there are a whole variety of reasons why levels of cortisol can be higher or lower in different children.

YOUNG: That's Joe Herbert, professor in the department of clinical neurosciences at the University of Cambridge in England. Their research claims that a high stress level - a high level of cortisol might indicate a child who's suffering depression. They've got a saliva test. We'll see where that goes. Professor Herbert, thanks so much for talking to us about it.

HERBERT: It's been a great pleasure.

YOUNG: You're listening to HERE AND NOW. Transcript provided by NPR, Copyright NPR.