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A saliva test for teenage boys with mild symptoms of depression could help identify those who will later develop major depression, a new study says.
Researchers measured the stress hormone cortisol in teenage boys and found that ones with high levels coupled with mild depression symptoms were up to 14 times more likely to suffer clinical depression later in life than those with low or normal cortisol levels.
The test was tried on teenage boys and girls, but found to be most effective with boys.
About one in six people suffer from clinical depression at some point in their lives, and most mental health disorders start before age 24.
"This is the emergence of a new way of looking at mental illness," Joe Herbert of the University of Cambridge and one of the study authors said at a news conference on Monday. "You don't have to rely simply on what the patient tells you, but what you can measure inside the patient."
Herbert compared the new test to ones done for other health problems, such as heart disease, which evaluate things such as cholesterol and high blood sugar to determine a patient's risk.
Herbert and colleagues observed more than 1,800 teenagers aged 12 to 19 and examined their cortisol levels and the teens' own reports of depression symptoms and tracked diagnoses of mental health disorders in them for up to three years later.
The boys who had high cortisol levels and mild depression symptoms were up to 14 times more likely to suffer from clinical depression when compared to other teens with normal levels, while girls with similarly elevated cortisol levels were only up to four times more likely to develop the condition.
Experts suggested that cortisol might affect boys and girls differently.
"All hormones, including sexual hormones, influence brain function and behavior," said Dr. Carmine Pariante, a professor of biological psychiatry at the Institute of Psychiatry at King's College London. He was not linked to the study.
Pariante said the gender-specific hormones — androgen for males and estrogen and progesterone for females — might react differently to cortisol and could explain the difference in risk.