Scientists claim to have moved a step closer to developing a new blood test that could detect whether a person is already suffering from depression. A team at Northwestern University in the US identified 11 new chemicals, or markers, in the blood that are linked to the psychiatric disorder.
These markers were found in different levels in teens with depression compared with their levels in those 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. A blood test, if developed, could make the diagnosis process easier, said Eva Redei, a Northwestern professor who was involved in the study.
These tests could help teens and 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, the researchers suggested.
In the new study, published in the journal Translational Psychiatry, Redei and her colleagues focused on early-onset depression that occurs in young adults before age 25. This disease, Redei said, is a distinct condition, different from adult-onset depression. 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 had identified in the animals to see if they held up in depressed humans. They tested 14 depressed and same number of non-depressed teens and found that 11 of the genetic markers distinguished between the teens with and without depression.
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."