It would be a huge breakthrough if doctors could screen for depression like they do for anemia... people could start getting treatment so much faster.

It currently can take YEARS to diagnose depression.

So this is a huge breakthrough in diagnosing AND in treating.

A new test that identifies particular molecules in the blood could help doctors diagnose patients with clinical depression, according to a new study published in the journal Translational Psychiatry. The blood test can also predict which therapies would be most successful for patients, and lays the groundwork for one day identifying people who are especially vulnerable to depression -- even before they’ve gone through a depressive episode.

But perhaps just as important, said lead investigator Eva Redei, Ph.D., is the potential the test has for taking some of the stigma out of a depression diagnosis. When depression can be confirmed with a blood test like any other physical ailment, she said, there’s less stigma about having the disease and getting treatment.

I'm also very intrigued by the finding that the specific marker is faulty RNA. This may be an easy to understand mind-body link that explains why so many depressed people ALSO suffer from various physical ailments. If depression hampers the ability to correctly copy protein building blocks, how can the body replicate itself properly?

It will be very interesting to learn if there's a causal relationship there, or if they're just correlated.

Overall it does seem like this is a very big breakthrough in understanding. 

Also, I didn't realize 6.7% of American adults suffer from depression:

Major depressive disorder affects an estimated 6.7 percent of the U.S. population and is the leading cause of disability for Americans ages 15 to 44, according to the Anxiety and Depression Association of America. Despite the research hurdles she still needs to overcome, Redei is confident that her test can make a positive impact on the millions who struggle with depression -- not only by making treatment more precise, but by bringing psychiatry "into the 21st century,” Redei said. “We’ll get to the point where there won’t be any discrimination between physical illness and mental illness.”

More:

This preliminary study of 32 adults aged 21 to 79 found that levels of these markers changed after 18 weeks of cognitive behavior therapy. The test was capable of detecting physical evidence that the therapy was working among patients who reported feeling less depressed after receiving therapy for this length of time. The researchers say this finding is especially promising since some patients in the study had not had any luck with antidepressant medications.