(Most mental health disorders start before age 24 and about one in six people will suffer from clinical depression, in the UK 10 million people will suffer at some point in their lives.
The research found that teenage boys who felt down and had high levels of the "stress hormone" cortisol were 14 times more likely to go on to suffer clinical depression than boys who didn't .
The test was tried on teenage boys and girls, but found to be most effective with boys.)