Can a psychiatric disorder be diagnosed with a blood test? That may be the future if two recent studies pan out. Researchers are figuring out how to differentiate the blood of a depressed person from that of someone without depression.
In the latest study, published today (April 17) in the journal Translational Psychiatry, researchers identified 11 new markers, or chemicals in the blood, for early-onset depression. These markers were found in different levels in teens with depression compared with their levels in teens who didn't have the condition.
Currently, depression is diagnosed by a subjective test, dependent upon a person's own explanation of their symptoms, and a psychiatrist's interpretation of them. These blood tests aren't meant to replace a psychiatrist, but could make the diagnosis process easier.
If a worried parent could have a family physician run a blood test, it might ease the diagnosis process during the already tough time of adolescence, said Eva Redei, a professor at Northwestern University in Evanston, Ill., who was involved in the study of the teen-depression blood test.
If they hold up to further testing, blood tests could help young adults, who often go untreated because they aren't aware of their disease, get treated. The biological basis of a blood test could also help to reduce that stigma, researchers suggest. [ 10 Facts About the Teen Brain ]
In the new study, Redei and her colleagues focused on early-onset depression, which occurs in teens and young adults before age 25. About 15 percent of young women and 7 percent of young men between ages 13 and 18 are estimated to have the disease.
This disease is a distinct condition, different from adult-onset depression, she said. In teens, "it has a somewhat greater genetic contribution, and also it has usually a harder course," Redei told LiveScience.
The researchers first looked at the genes of rats that had been bred to be either more or less depressed, considered the "genetic model." Next, they looked at four different strains of rats placed under chronic stress, an environmental factor that causes depression. They compared the gene-expression changes, which can occur as a result of stress, between the chronically stressed rats and individuals without extra stress.
The researchers then took 26 gene-expression changes they'd identified in the animals to see if they held up in depressed humans; they tested 14 depressed and 14 non-depressed teens. Eleven of the genetic markers faithfully distinguished between teens with and without depression.
Building to a blood test
In an earlier study, published in the Feb. 28 issue of the journal Molecular Psychiatry, researchers focused on a blood test for adult-onset depression. The researchers used nine markers, consisting of proteins and other body chemicals that had previously been identified as related to depression and brain functioning.
With these markers, they came up with a formula to give each patient's blood test a score, which indicated the likelihood of having depression.
The researchers analyzed the blood of 70 depressed adults and 43 non-depressed controls. The average score of the depressed patients was 85, and the score of the non-depressed patients was 33. The researchers said the test could detect depression in 90 percent of people who actually have the condition.
"We expect that the biological basis of this test may provide patients with insight into their depression as a treatable disease rather than a source of self-doubt and stigma," John Bilello, chief scientific officer of Ridge Diagnostics, which makes the blood test and sponsored the study, said in a statement.
Brain and the blood
Redei also said that a blood test could also help remove some of the stigma attached to depression.
"Only about 25 percent of depressed teens are being treated," she said. "It has to do with the fact that they have to go through this process to be diagnosed, and then there is a stigma attached to it."
Because a blood test provides physical evidence of a disease, it could help counter misconceptions about depression, such as that it is all in a person's head, or is a sign of some personal weakness, the reasoning goes.
"It will help remove that stigma, if we have something you can attach a number to," Redei said."Eventually the whole society will accept that this disease, depression, isn't something you can just get over by pulling yourself up."
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