The authors say that diagnosing depression in teenagers can be especially challenging, partly because moods tend to fluctuate anyway during adolescence. However, prompt and accurate diagnosis during this age period is important.
In what the authors describe as a "major breakthrough", this blood test can also distinguish between major depression and depression combined with anxiety disorder - i.e. it can tell different subtypes of depression apart.
Eva Redei said:
"Right now depression is treated with a blunt instrument. It's like treating type 1 diabetes and type 2 diabetes exactly the same way. We need to do better for these kids.
This is the first significant step for us to understand which treatment will be most effective for an individual patient. Without an objective diagnosis, it's very difficult to make that assessment. The early diagnosis and specific classification of early major depression could lead to a larger repertoire of more effective treatments and enhanced individualized care. "
Major depression prevalence among children ranges from 2% to 4% among pre-adolescent kids, to 10% to 20% for late-teenagers. Teenagers with depression who remain untreated have a higher risk of substance abuse, physical illness, suicide and social maladjustment - their disease is also much more likely to continue well into adulthood.
The teens with depression involved in this study were all patients of co-first author, Kathleen Paier, M.D. and colleagues from the Research Institute of Nationwide Children's Hospital in Columbus, Ohio. Study participants included 28 adolescents, 14 who had major depression and had not been clinically treated and 14 "healthy" individuals. They were aged between 15 and 19 years. Control subjects and the depressed ones were matched by race and sex.
Blood samples were taken from all 28 teenagers and tested for 26 genetic blood markers that Redei and team had identified in previous research. They found that 11 of the markers could pick out depressed from non-depressed adolescents. Additionally, 18 of the 26 markers could identify those with only major depression, as well as individuals with a combination of depression with anxiety disorder.
Co-author, Brian Andrus, carried out the blood analysis. He was blind to the participants' depression status.
"These 11 genes are probably the tip of the iceberg because depression is a complex illness. But it's an entree into a much bigger phenomenon that has to be explored. It clearly indicates we can diagnose from blood and create a blood diagnosis test for depression."
Redei's work is the result of decades of research on severely depressed and anxious rates. These laboratory animals have similar signs and symptoms related to depression and anxiety found in humans.
The authors explained that getting teenagers to agree to treatment for depression is "challenging". None of the participants who were diagnosed with depression opted for treatment.
"Everybody, including parents, are wary of treatment, and there remains a social stigma around depression, which in the peer-pressured world of teenagers is even more devastating. Once you can objectively diagnose depression as you would hypertension or diabetes, the stigma will likely disappear."