Image copyright SPL Image caption The findings identify risk of clinical depression among boys but not girls

A tool for predicting the risk of clinical depression in teenage boys has been developed by researchers.

Looking for high levels of the stress hormone cortisol and reports of feeling miserable, lonely or unloved could find those at greatest risk.

Researchers at the University of Cambridge want to develop a way of screening for depression in the same way as heart problems can be predicted.

However, their method was far less useful in girls.

Teenage years and early adulthood are a critical time for mental health - 75% of disorders develop before the age of 24.

But there is no way to accurately say who will or will not develop depression.

Risky combination

Now researchers say they have taken the "first step" towards a screening tool.

Tests on 1,858 teenagers, reported in Proceedings of the National Academy of Sciences, combined hormone levels and mood questionnaires to assess risk.

They showed that having both high cortisol levels and depressive mood symptoms posed a higher risk of depression than either factor alone and presented a risk of clinical depression 14 times that of those with low cortisol and no depressive symptoms.

Around one in six boys was in the high-risk category and half of them were diagnosed with clinical depression during the three years of study.

One of the researchers, Prof Ian Goodyer, said: "Depression is a terrible illness that will affect as many as 10 million people in the UK at some point in their lives.

"Through our research, we now have a very real way of identifying those teenage boys most likely to develop clinical depression.

"This will help us strategically target preventions and interventions at these individuals and hopefully help reduce their risk of serious episodes of depression, and their consequences, in adult life."

'Many contributory factors'

Women are twice as likely as men to develop depression during their lifetimes, but the test was little help in determining risk.

One theory is that women naturally have higher cortisol levels, which affects their risk.

However, the test is not yet ready for clinical use.

Dr John Williams, from the Wellcome Trust, which funded the study, said: "Progress in identifying biological markers for depression has been frustratingly slow, but now we finally have a biomarker for clinical depression."

Sam Challis, from mental health charity Mind, said: "This study claims there is a biomarker linked to depression, but it's important to bear in mind that many factors play a part in depression, such as life events, genetic factors, side effects of medication and diet.

"However, this research could help identify those who may need extra support.

"We know that it is possible to recover from a mental health problem, and this is more likely for those who seek help straight away."