But the discovery does not mean the test can be offered to the public just yet, officials said.
It is also one of the toughest mental illnesses to treat.
The new study found that adults with depression have markers in their blood — levels of certain molecules — that indicate the disease, said Eva Redei, a professor of psychiatry and behavioral sciences at Northwestern’s Feinberg School of Medicine who helped develop the test.
Blood work can also indicate if treatment is working.
“If we had an objective, laboratory-based blood test just like a cholesterol test or glucose test, we could reduce the stigma of depression,” said Redei, who joined Northwestern’s faculty in 1996.
“Most clinical laboratories already have the equipment to do this test. It’s a fast test that is not difficult to conduct. The technology is already there,” Redei said. “We hope that in the future we can make the data simpler so that truly any lab can do it.”
For 16 years, Redei has been working to develop a scientific way of diagnosing depression, she said Monday. She started her work in laboratory animals and eventually was able to study humans.
She already has developed a blood test that diagnoses depression in adolescents, she said. But her new study shows that the markers in the bloodstream that identify depression in youths are different from the markers in adults.
The results of Redei’s most recent study will be published in the journal Translational Psychiatry. She is co-lead author of the study, along with six other scientists.
To develop their test, Redei and the other scientists examined 32 patients ages 21 to 79 who had been independently diagnosed as depressed. They also tested the blood of 32 adults who weren’t depressed. After studying all the patients’ blood work, the researchers found common markers, or molecular levels, in the patients who were depressed and those who were not.
The researchers also tested the patients after they underwent 18 weeks of therapy. The tests were able to determine which patients had benefited from the treatment and which ones remained depressed.
“I would really like to see if the test can predict which antidepressant would be beneficial for which patient,” she said. “Of course, the process is very long.”
Now that the results of this study are complete, Redei said she is seeking funding to repeat the experiment in more adults. She also wants to determine whether a blood test can differentiate between major depression and bipolar depression. If her study proves true on a larger sampling of adults, the test could eventually be developed into a U.S. Food and Drug Administration-approved product.