Researchers at Northwestern Medicine say they have developed the first blood test to diagnose major depression in adults. The assay, which works by measuring the levels of nine RNA blood markers, also predicts who will benefit from cognitive behavioral therapy based on the behavior of some of the markers.
In addition, the test showed the biological effects of cognitive behavioral therapy, the first measurable, blood-based evidence of the therapy's success. The levels of markers changed in patients who had the therapy for 18 weeks and were no longer depressed.
"Blood transcript levels of nine markers of ADCY3, DGKA, FAM46A, IGSF4A/CADM1, KIAA1539, MARCKS, PSME1, RAPH1, and TLR7, differed significantly between participants with MDD [major depressive disorder] (N=32) and ND [nondepressed] controls (N=32) at baseline (q< 0.05)," wrote the investigators in their study (“Blood transcriptomic biomarkers in adult primary care patients with major depressive disorder undergoing cognitive behavioral therapy”) published in Translational Psychiatry. "Abundance of the DGKA, KIAA1539, and RAPH1 transcripts remained significantly different between subjects with MDD and ND controls even after post-CBT [cognitive behavioral therapy] remission (defined as PHQ-9 <5)."
"This clearly indicates that you can have a blood-based lab test for depression, providing a scientific diagnosis in the same way someone is diagnosed with high blood pressure or high cholesterol," said Eva Redei, Ph.D., who developed the test and is a professor of psychiatry and behavioral sciences at the Northwestern University Feinberg School of Medicine. "This test brings mental health diagnosis into the 21st century and offers the first personalized medicine approach to people suffering from depression."
Dr. Redei, who is co-lead author of the study, previously developed a blood test that diagnosed depression in adolescents. Most of the markers she identified in the adult depression panel are different from those in depressed adolescents.
The current method of diagnosing depression is subjective and based on nonspecific symptoms such as poor mood, fatigue, and change in appetite, all of which can apply to a large number of mental or physical problems. A diagnosis also relies on the patient's ability to report his symptoms and the physician's ability to interpret them. But depressed patients frequently underreport or inadequately describe their symptoms.
"Mental health has been where medicine was 100 years ago when physicians diagnosed illnesses or disorders based on symptoms," said co-lead author David Mohr, Ph.D., a professor of preventive medicine and director of the Center for Behavioral Intervention Technologies at Feinberg. "This study brings us much closer to having laboratory tests that can be used in diagnosis and treatment selection."
The new blood test will allow physicians for the first time to use lab tests to determine what treatments will be most useful for individual patients.
Major depressive disorder affects 6.7 percent of the U.S. adult population in a year, a number that is rising. There is a two- to 40-month delay in diagnosis, and the longer the delay, the more difficult it is to treat depression. An estimated 12.5 percent of patients in primary care have major depression but only about half of those cases are diagnosed. A biologically based test has the potential to provide a more timely and accurate diagnosis.