Checking the spit of teenage boys who report mild symptoms of depression could help better identify those more likely to develop long-lasting mental illness later in life, NBC News reports.

Researchers from the University of Cambridge in the United Kingdom developed a test that measures levels of the so-called “stress hormone” cortisol. Scientists linked the chemical’s presence specifically in teenage boys to an increased risk that these kids will become clinically depressed.

For the study, University researchers looked at cortisol levels from more than 1,800 teens between ages 12 and 19, along with self-reported accounts of their depression symptoms. The scientists then tracked the teenagers’ histories of mental health disorders for three years.

By the end of the study, teen boys who had high levels of cortisol in their saliva and mild depression symptoms at the time of the study were nearly 14 times more likely to suffer from clinical depression later in life when compared with boys who had normal cortisol levels.

“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 and one of the study authors. “You don’t have to rely simply on what the patient tells you, but what you can measure inside the patient.”

Interestingly, teen girls with elevated cortisol levels involved in the study were only up to four times more likely to develop clinical depression. Researchers said the findings suggest that cortisol might affect male and female brains differently.

Scientists said using cortisol as an effective marker for depression could help at-risk youth begin treatment earlier, and it could yield better mental health outcomes in the long run.

Studies show African Americans are less likely to seek treatment for mental disorders than other ethnic groups. Click here to learn more about depression in the black community and the steps you can take to stop the silence.