A new study suggests that a simple blood test can now accurately screen for depression and even identify the treatment therapy most likely to succeed.
For centuries, depression was a mysterious, unpredictable condition. Since there were no typical physical symptoms, and since it left no visible evidence on the body – no pockmarks, no bleeding, no coughing, no visible scars – people questioned its authenticity as a "disease."
Through the years, people suffering with the mental illness would hear things like, "There's nothing wrong with you! Pull yourself up by the bootstraps and get on with your life."
The End of Depression's "Stigma"?
In addition to helping doctors identify and treat people with depression -- and even detect in advance those patients likely to experience depressive episodes in the future -- this new blood test provides evidence that depression is biologically very real -- like cancer, pneumonia, diabetes, Alzheimer's, and Parkinson's.
Now, as with other diseases, observable biological causes can be assigned to depression, and DNA test results may even suggest potential targeted treatments. The new blood test could help eliminate – once and for all -- the unfortunate "stigma" that has so long accompanied depression. That stigma has prevented countless sufferers from coming forward to seek help.
With her team, Dr. Eva Redei, a neuroscientist and professor at the Northwestern University Feinberg School of Medicine, took blood samples from 32 patients 21-79 years old who – through clinical interviews – had been diagnosed with depression. The researchers then compared those samples with blood from 32 people within that same age range without depression -- the control group.
Three conclusions emerged:
1) The researchers discovered nine RNA markers – molecules the carry out instructions from the DNA – that varied significantly between the two groups. The team at Northwestern assigned those markers as the basis for diagnosing depression.
2) The 32 depressed patients then underwent 18 weeks of cognitive behavioral therapy, a common treatment for depression. After that interval, Dr. Redei retested their blood. She found she could identify the patients who had most benefited from the therapy simply by observing the changes in their RNA markers. Put another way, the second sampling provided biological evidence of the treatment's effectiveness.
3) The researchers identified three RNA markers that didn't change from the first test to the second, regardless of the patient's level of improvement. Redei suspected those three unchanging markers indicated predisposition to depression – another potential bonanza for clinicians... and their patients.
Co-lead author Dr. David Mohr said:
Being aware of people who are more susceptible to recurring depression allows us to monitor them more closely. They can consider a maintenance dose of antidepressants or continued psychotherapy to diminish the severity of a future episode or prolong the intervals between episodes.
More Biological Evidence for Depression
Dr. Zachary Kaminsky, at the Mood Disorders Center at Johns Hopkins Medicine, also weighed in on the study's findings. He wasn't involved in the study, but he had pioneered an earlier blood test to predict suicide risk. In his own research, Kaminsky had measured very different things than Redei and her team. Still, he thinks his own research shares something basic in common with Redei's: an effort to create biological tests and evidence for mental illness.
It's an exciting time -- there is potential to find factors that are going to distinguish between various mental illnesses as well as responses to direct clinical treatment. Any finding that gets us closer to that is very interesting and worth following up.
Kaminsky and Redei both agree that her recent findings need to be replicated in larger test groups before the FDA would consider approving the blood test.
There's another issue, too. Said Redei, "The major question here is always funding. We are really trying to gather as much funding from as many sources as possible so it can move ahead."
The Anxiety and Depression Association of America estimates that major depressive disorder -- the leading cause of disability for Americans ages 15 to 44 -- affects 6.7 percent of all Americans.
Redei hopes her work can help bring psychiatry into "the 21st century. We'll get to the point where there won't be any discrimination between physical illness and mental illness."
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Here is Northwestern University's September 14, 2014 press release announcing the study's results. 
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