For decades, doctors have been relying on small vials of your red stuff to tell them important information about your heart, kidneys, and other organs. Now, your brain might be able to join the party: Researchers from Northwestern University recently developed a new blood test that can help diagnose depression in adults .

Scientists measured the blood levels of nine specific markers of RNA—the “messengers” that interpret DNA’s genetic code—in people with depression and those without, and found that they were significantly different in people who suffered from the condition. 

After the participants with depression completed 18 weeks of cognitive behavioral therapy, the blood tests were repeated again. About 40 percent of them recovered fully, and their levels of certain markers differed from those who were still depressed. 

In the future, this data may be able to help researchers determine who will respond to this type of therapy, says study author Eva Redei, Ph.D.

Interestingly, three specific markers remained different in the depressed people compared to the non-sufferers, whether or not those with the condition recovered with treatment. That means the test also has the potential to predict people who might be vulnerable to developing depression down the line—even before they might begin experiencing symptoms.

Currently, depression is diagnosed based on the symptoms a patient reports and a clinical interview with a doctor. (Another company does offer a blood test for depression, though it’s not based on genetic markers and its testing is only performed at their lab.) Having an objective, biologically-based test can solidify a diagnosis, help the patient believe that he truly has a medical condition, and reduce the stigma associated with it.

“It can help people understand that it’s really not their fault, and therefore, they can go and get treatment,” says Redei. 

There is still work that needs to be done before the test can make its way to your doctor’s office: The researchers plan on another larger-scale study to replicate the test’s diagnostic findings, as well as additional studies to explore other components, such as whether it would be able to predict recovery after antidepressant use.

“In the future, this psychiatric illness will become like any other illness, which you can objectively determine what the patient has, and objectively determine which treatment they should get,” she says.

In the meantime, if you experience persistent feelings of sadness, hopelessness, worthlessness, loss of energy, or irritability, or if you notice a loss of interest in enjoyable hobbies or find you have trouble sleeping, make an appointment with your doctor. He or she can rule out any physical conditions as the cause of your symptoms, and may refer you to a mental health professional to help determine a diagnosis and a treatment plan.

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