U.S. researchers have successfully tested a blood test for depression. And it not only could help diagnose and treat patients, but it could also help remove the stigma of a common mental illness.

Depression is one of the most common of all mental disorders, says the Northwestern University psychiatry professor who developed the test, Eva Redei, PhD.

“The World Health Organization estimates that about 350 million people suffer from depression yearly,” she noted in a telephone interview, adding,  “That number is probably underestimated.”

Depression is typically diagnosed in an interview with a therapist, but Redei says she looked for a biological test because of how she views depression.

“I think it came from my firm belief that depression is an illness, just like any other illness is. And if it is an illness, that means you can also diagnose it in an objective manner,” she said.

Her test measures nine characteristics, or markers, in the blood. The results can tell a doctor whether a patient is depressed.

And Redei says blood markers showed improvement as patients went through psychotherapy treatment for their depression.

“So that is suggestive,” she said, “that perhaps we can follow the way the patients respond to treatment by measuring these markers in the blood.”

This was a small study, and there’s still more research to be done before a blood test for depression is available to doctors. But Redei says she is “sure” that one day, blood tests may also be developed for other mental illnesses.

Her study is published online by the journal Translational Psychiatry.  
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