New research shows that depression is significantly more likely to occur in teenage boys with elevated levels of the “stress hormone” cortisol, illuminating a possible biological marker for the difficult condition that one in six will experience at some point in their life.

Dr. Ian Goodyer, a professor at the University of Cambridge and lead author of the new study, said in a press release that the findings will pave the way for more effective preventative strategies. "Depression is a terrible illness that will affect as many as ten million people in the UK at some point in their lives," he explained. "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."

The study, which is published in the journal Proceedings of the National Academy of Sciences, found that teenage boys who show a combination of depressive symptoms and elevated levels of cortisol may constitute a previously overlooked risk group for major depressive disorder. For their investigation, the researchers compared saliva samples and self-reported psychiatric health in two young cohorts. Data was collected on two occasions separated by a year.

The team found that boys with high levels of cortisol in the morning and high incidence of symptoms associated with depression were 14 times more likely to develop major depressive disorder compared to boys with normal levels of cortisol and low depression symptoms over time. "This new biomarker suggests that we may be able to offer a more personalised approach to tackling boys at risk for depression,” first author Dr. Matthew Owens added. This could be a much needed way of reducing the number of people suffering from depression, and in particular stemming a risk at a time when there has been an increasing rate of suicide amongst teenage boys and young men."

What Causes Depression, Really?

The current study is the latest in growing series of attempts to identify so-called biomarkers indicative of depression — that is, biological rather than psychiatric signs of the condition. Another example is a 2013 study from Brigham Young University, in which researchers show that depression may arise from difficulties in processing certain memories. Similarly, a study from the University Heart Center in Hamburg shows that major depressive disorder may be tied to arterial fibrillation, or irregular heartbeat.

"Progress in identifying biological markers for depression has been frustratingly slow, but now we finally have a biomarker for clinical depression,” Dr. John Williams, a researcher at the Wellcome Trust who helped fund the current study, told reporters. “The approach taken by Professor Goodyer's team may yet yield further biomarkers. It also gives tantalising clues about the gender differences in the causes and onset of depression."

Source: Owens M, Goodyer I, et al. Elevated morning cortisol is a stratified population biomarker for major depression in boys only with high depressive symptoms. PNAS. 2014.