(Inside Science TV) -- Analyzing a single drop of blood can reveal almost any virus, many cancers, your cholesterol level and information for diabetics. Now, for the first time, your blood can help diagnose your mental health.
"What we found is a panel of markers that have different levels in patients with depression," said Eva Redei, a neuroscientists at Northwestern University in Chicago, Illinois.
Redei and her team have found signs in the blood that could change how depression is diagnosed.
"Depression is truly one of those illnesses that have been diagnosed very subjectively," she said.
Today, more than 1 in 10 people in the United States are living with depression. It's estimated at least half of the people who are depressed are not diagnosed at all, explained Reidei.
"We also know that primary care doctors only diagnose about 50 percent of them correctly," said Redei. "It's basically a conversation."
That's because right now, diagnosis is based on a battery of questions asked in the doctor's office.
But this blood test could take the guesswork out of diagnosing depression and give further evidence that depression is a physiological illness.
The test looks at levels of nine RNA blood markers. RNA is the molecule that carries out instructions from DNA genetic code. It acts as a messenger to create proteins that perform important functions in our body's cells.
The RNA markers look different in patients with depression versus those who don't have depression.
A study of 32 adults found that levels of these markers changed after 18 weeks of cognitive behavior or talk therapy.
The change in blood markers showed the test could detect physical evidence that the therapy was working among patients who said they felt less depressed after therapy. "It's really the first time to see objective biological blood-based markers for cognitive behavioral therapy. I didn't believe it. I mean I was so surprised that it occurred, but it did," said Redei.
The test could be useful for diagnosing and determining the best course of treatment for patients with depression.
"The patient will know with the security that they do or do not have depression," said Redei.