Northwestern researchers develop blood test to diagnose depression and predict treatment success

A blood test to diagnose major depression in adults has been developed by Northwestern University Feinberg School of Medicine scientists. The test identifies depression by measuring the levels of nine RNA blood markers whose levels are significantly different in depressed patients from those of controls. The blood test also predicts who will benefit from cognitive behavioral therapy based on the behavior of some of the markers. Details appear in a study recently published in Translational Psychiatry.

The study included 32 patients, ages 21 to 79, who had been independently diagnosed as depressed in a clinical interview, and 32 non-depressed controls in the same age range. Some of the patients had been on long-term antidepressants but were still depressed. The patients also were participating in a previously reported study comparing the effectiveness of face-to-face and telephone-administered cognitive behavioral therapy.

After 18 weeks of therapy, the changed levels of certain markers could differentiate patients who had responded positively and were no longer depressed (based on a clinical interview and patients’ self-reported symptoms) from patients who remained depressed. This is the first biological indicator of the success of cognitive behavioral therapy, the study authors said.

In addition, the blood test predicts who will benefit from the cognitive behavioral therapy based on a distinct pattern or fingerprint of the levels of the nine marker levels at baseline in patients who recover from depression as a result of the therapy. The blood levels of these markers did not show this pattern in the patients who did not improve with the therapy.

“This clearly indicates that you can have a blood-based laboratory test for depression, providing a scientific diagnosis in the same way someone is diagnosed with high blood pressure or high cholesterol,” says co-lead author Eva Redei, PhD, who developed the test.