Researchers from the United Kingdom led by Professor Ian Goodyer from the University of Cambridge announced the discovery of the first true and successful biomarker for clinical depression in the Feb. 17, 2014, edition of the journal Proceedings of the National Academy of Sciences.
Elevated levels of the hormone cortisol measured in the saliva of two different cohorts of adolescents indicated a direct correlation with self-reported depression and rates of suicide.
The researchers examined the cortisol levels in the saliva of 660 adolescent males for four consecutive days at the same time in the morning and then at one time a year later. The second study involved 1,198 adolescents that had cortisol levels in their saliva analyzed from three consecutive days.
The results from both groups were found to be so well correlated with self-reported symptoms of depression that the researchers could separate the study participants into four distinct groups based on the cortisol levels in their saliva.
The adolescent males with the highest levels of cortisol in their saliva were found to be 14 times more likely to suffer from clinical depression. Girls with high cortisol content in their saliva were four times as likely to have clinical depression.
The researchers note that almost 17 percent of all people will suffer from clinical depression at some time in their lives.
The quick and simple test for elevated cortisol in saliva is expected to reduce high levels of adolescent suicide caused by depression as well as provide a clear marker for early treatment.