Researchers at the University of Cambridge may have found a way of predicting which teenagers will later develop major depression - through a saliva test.
However the test will only be able to predict the mental health issue in males.
A saliva test measuring the stress hormone cortisol in teenage boys was coupled with the teenage boys’ personal report of depression symptoms.
Three years on, those who had had high levels of cortisol as well as mild symptoms of depression, were shown to be up to 14 times more likely that those with low or normal levels of cortisol to be subject to clinical depression later in life.
The study, funded by the Wellcome Trust, was published online in the journal Proceedings of the National Academies of Science on Monday.
The trust's researchers said they hope the biomarker will “enable primary care services to identify boys at high risk and consider new public mental health strategies for this subgroup in the community".
“Depression is a terrible illness that will affect as many as ten million people in the UK at some point in their lives,” said Professor Ian Goodyer from the University of Cambridge, who led the study.
”This [discovery] 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.”
"This is the emergence of a new way of looking at mental illness," said Joe Herbert, Emeritus Professor of Neuroscience at the University of Cambridge.
"You don't have to rely simply on what the patient tells you, but what you can measure inside the patient."
This test was tested on both teenage boys and girls, but findings have shown that it is most effective with boys.
Dr John Williams, Head of Neuroscience and Mental Health at the Wellcome Trust, was optimistic about the finding, saying it "provides us with tantalising clues about the gender differences in the causes and onset of depression”.
The test is not ready for clinical use just yet, but this is an important first step.
If it is to be eventually used in clinical practice one of the benefits is that it could be "elegant in its simplicity", as Dr Oliver Howes, spokesperson for European College of Neuropsychopharmacology (ECNP) put it.