After testing both boys and girls who had been diagnosed with mild depression, the researchers found that boys with high levels of a stress hormone called cortisol were 14 times more likely to be diagnosed with clinical depression later, according to the Associated Press.
Girls with high cortisol levels were only four times more likely to receive such a diagnosis during the course of the study, the AP reported.
At this point in time, there is no biological way to measure depression risk, the news service reported.
"This is the emergence of a new way of looking at mental illness," study co-author Joe Herbert, of the University of Cambridge, told reporters during a Monday news conference. "You don't have to rely simply on what the patient tells you, but what you can measure inside the patient."
In the study, published online Monday in the Proceedings of the National Academy of Sciences, saliva samples were collected from more than 1,800 children aged 12 to 19. The teens were also questioned about depression symptoms, and all were followed for at least three years.
Experts told the AP that male and female hormones might react differently to cortisol, and that might explain the stronger correlation between the hormone and depression risk in males.