In a small but significant study, researchers have identified biological markers in the bloodstream that physicians could use to diagnose depression in adolescents.

The goal is to develop a blood test that could be used easily and widely to pinpoint early-onset major depressive disorder. Such a test would particularly be of use to primary care physicians, said Eva E. Redei, PhD, senior study author and David Lawrence Stein Professor of Psychiatric Diseases Affecting Children and Adolescents at Northwestern University Feinberg School of Medicine in Chicago.

Of all age groups, adolescents see doctors the least. When they do, they most often see a primary care physician.

“This is an exciting study,” said Robert Scott Benson, MD, speaker-elect of the American Psychiatric Assn. Assembly and a child and adolescent psychiatrist in Pensacola, Fla. “It is one of many we expect to see that will help us improve our understanding of depression.”

Major depression affects about 11% of adolescents ages 13 to 18, according to the National Institute of Mental Health. But estimates are probably under-counted, because there is no objective way to diagnose the disorder, Redei said. Instead, physicians must interpret patients’ descriptions of their symptoms. That can be especially challenging with adolescents.

“Teenagers are not easy to communicate with,” she said. “Our current diagnostic methods have worked, but they have not worked as well as they could.”

In the study, published online April 17 in Translational Psychiatry, researchers analyzed 28 biomarkers in rats and identified 11 linked to early-onset major depression. They then confirmed the results in a blinded study of 28 patients 15 to 19 years old, including 14 previously diagnosed with early-onset major depressive disorder and 14 without the disorder. Redei said the research team is planning a study involving at least 200 patients.

Having an impartial diagnostic method would help remove some of the stigma and improve treatment of major depression, Dr. Benson said. In adolescents, the disorder can interfere with development and school performance and make them more prone to substance abuse.

Being able to link depression to reliable biological markers will strengthen evidence that it is an illness. For physicians treating the disorder, understanding the biological mechanisms behind it will help them identify the best treatments, he said.

It also will help young patients and their parents understand that no one is at fault.

“Stigma continues to be a major barrier to families seeking treatment,” Dr. Benson said.

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