April 17, 2012 -- Blood tests have long been the diagnostic standard for diagnosing teenage diseases, such as mono and diabetes. Now researchers have developed a blood test that can diagnose depression in teens, a step they hope will lead to a better way to identify the disorder in young people.
Currently, diagnosing depression depends entirely on a patient's willingness to report symptoms -- and a doctor's ability to interpret them. For teens, the diagnosis is particularly challenging, given the natural emotional ups and downs of adolescence.
"Teenagers are extraordinarily vulnerable to depression," said Eva Redei, author of the study and a professor of psychiatry and behavioral medicine at the Northwestern Feinberg School of Medicine in Chicago. "And there are no objective, biological measures for evaluating them for depression."
In the study, published today in the journal Translational Psychiatry, Redei and her team developed a test that looks for markers in the blood of teens with major depressive disorder. By studying rats that had genetic and environmental predispositions for depression, the researchers were able to pinpoint 26 markers of major depression.
They looked for these markers in the blood of 28 human teenagers, ages 15 to 19, half with depression and half without. They found that 11 of the markers showed up in the depressed teens but not in teens without depression.
They were also able to distinguish different subtypes of depression, successfully identifying teens who suffered from depression alone and depression combined with anxiety disorders.
"The uniqueness of this study is that we showed that it can be done. The technology is available to make this diagnosis," Redei said.
Experts say there is a great need to diagnose depression early in life, particularly among teens.
According to the National Institute of Mental Health, 11 percent of 13- to 18-year-olds develop major depression at some point in their adolescence. Reports from the Substance Abuse and Mental Health Services Administration are slightly lower – in 2008, 8.3 percent of 12- to 17-year-olds dealt with depression.
The disorder puts teens at greater risk for other health dangers, including substance abuse, physical illness and suicide. Also, when depression begins earlier in life, the chances that it will persist and perhaps worsen in adulthood are great.
The study is not the first to try to formulate a blood test for major depression. In February, researchers at Massachusetts General Hospital analyzed blood from depressed adults and found that the levels of nine biomarkers differed from those without the disorder. Redei said her test is different because it identifies blood markers not previously linked to depression.
Some experts are not so sure how useful a blood test can be in identifying and treating teens with depression. The study authors say they are hopeful that a blood test diagnosis for depression will help more teens get the treatment they need. But none of the teens who were diagnosed in the study opted for any treatment.
"A blood test doesn't show the dynamics of what the particular person is dealing with, where their depression is coming from. You've got to explore it at a much deeper level than just a blood test," said Elaine Leader, a psychiatrist and the executive director of TEEN LINE, a mental health hotline for California teens.
Dr. Carol Bernstein, an associate professor of psychiatry at New York University Langone Medical Center, said biologic testing doesn't get at the complex interactions of genes, biology and environment involved in depression.
"I think people are looking for a magic bullet, a single answer. But these disorders are much too complicated," she said. "But certainly the more tools we have the better."
Redei said developing a blood test is important not just for diagnosing patients, but also reducing the stigma associated with having depression.
"The fact that there are no objective biological measures for depression is probably a major contributor to the stigma," Redei said. "Once it's a medically proven objectively measured illness, the stigma sooner or later has to diminish or even disappear."
Redei and her colleagues are currently testing how well the blood test works in adults with depression.