Blood Test May Help Diagnose Depression

A blood test may eventually help diagnose depression, according to a new study published in the journal Molecular Psychiatry.

 In the study, which was  funded by Ridge Diagnostics, the firm that developed the blood test,  researchers at Massachusetts General Hospital in Boston analyzed the levels of nine biomarkers that could  distinguish patients who had a major depressive disorder from those who did not.

The biomarkers analyzed were associated with inflammation, neuron development and stress response in brain structures. The blood test results were then scored on a scale that researchers created for the study.

"Traditionally, diagnoses of major depression and other mental disorders had been made based on patients' reported symptoms, but the accuracy of that process varies a great deal, often depending on the experience and resources of the clinician conducting the assessment," Dr. George Papakostas, lead author of the study, said in a statement." Adding an objective biological test could improve diagnostic accuracy and may also help us track individual patients' response to treatment."

The pilot study included 36 adults who had been diagnosed with major depression, and 43 healthy control study subjects.  The test accurately pinpointed depression in  90 percent of previously diagnosed depressed patients.

Many patients deny they are depressed because of the stigma associated with depression, said Dr. Harold Koenig, a professor of psychiatry and behavioral sciences at Duke University Medical Center, so the test could be useful in taking away the shame of the disease and getting more people  treated, he said.

But a blood test diagnosis can come with a big downside.

"[Some] patients might truly have depression and have a negative test, and then their symptoms might be discounted by family members and by health professionals, since depressive symptoms or emotional feelings are entirely subjective and there  is no way to verify these symptoms," said Koenig.  "This could place a huge burden on patients who are already suffering, and be told that they really don't have depression because they had a low score on a less than perfect test."

The biomarkers could also be influenced by other disease patterns, said Cynthia Kuhn, a  professor of pharmacology at Duke University Medical Center.

"It will be important to see if [the blood test] can discriminate depression from related disorders," said Kuhn. "It is unlikely that the blood test alone would be appropriate."

It is important that physicians focus on patients' symptoms, along with biologic and genetic factors, said Dr. Carol Bernstein, associate professor of psychiatry at the New York University School of Medicine.

"Patient-centered care should be exactly that and outside of specific diseases that have clear genetics … medicine cannot be reduced to simple tests," said Bernstein. "Disease states are complex and depression is no exception."