Further, another panel of partially overlapping blood biomarkers differentiated teens who had MDD together with anxiety disorder from those who only had MDD.
"This is the first step toward having a clinical diagnostic test for early-onset major depression," study investigator Eva E. Redei, PhD, from the Department of Psychiatry and Behavioral Sciences, Feinberg School of Medicine, Northwestern University, Chicago, told Medscape Medical News.
"Should larger studies confirm and extend our findings, it could also lead to development of different individualized treatment strategies," she added.
"Despite considerable efforts, there are still no valid, reliable and feasible peripheral/blood biomarkers that can diagnose MDD, classify MDD subtypes and measure treatment response, even in adult-onset MDD. Our research is unique in the attempt to discover a biomarker panel for early-onset MDD, a more severe disorder than adult onset," the researchers note in their report.
The study was published April 17 in Translational Psychiatry.
Tip of the Iceberg
The investigators identified a panel of 26 blood biomarkers associated with both genetic and environmental stress-related types of depression in animal models. They carried out unbiased, blinded analyses of this combined set of 26 candidate blood transcriptomic markers in 14 young people aged 15 to 19 years who had MDD and 14 age-matched healthy control participants.
A panel of 11 biomarkers differentiated teens with early-onset MDD from healthy teens. These candidate biomarkers are derived almost equally from the genetic and chronic stress animal models of depression, the investigators say. The genes expressing these transcripts belong to 3 broad functional categories: those involved in transcription, neurodevelopment, and neurodegeneration.
"These 11 genes are probably the tip of the iceberg because depression is a complex illness," Dr. Redei commented in a prepared statement. "But it's an entree into a much bigger phenomenon that has to be explored."
The researchers also found that a separate but partially overlapping panel of 18 transcripts distinguished youths who had MDD with comorbid anxiety from those with MDD alone. "Only six gene transcripts were in both panels, and thus the majority of these markers are unique to this diagnostic category," the authors write
In addition, they note that the panel differentiating MDD youths with comorbid anxiety disorders from those without such disorders had a substantially higher number of genes derived from the chronic stress model than from the genetic model. "These latter observations support the long-standing clinical impression that MDD with comorbid anxiety disorders is a unique phenotype," they add.
Limitations to the current study included the small sample size and the limited number of target transcripts pursued.
"Additionally, we recognize that the animal models only mirror some aspects of early-onset MDD and, therefore, the markers derived from them cannot be all inclusive," the authors write.
"An ongoing study is evaluating our panel of markers on adults. We would like to test the validity and specificity of our diagnostic panel in a larger study involving teens during a depressive episode and after they remitted. Hopefully, others will also get involved in this process; we welcome the interest," said Dr. Redei.
The human study was funded by grants from the Research Institute of Nationwide Children's Hospital in Columbus, Ohio. The animal research was supported by grants from the Davee Foundation, the RD Foundation, and the National Institutes of Health. The authors have disclosed no relevant financial relationships.
Transl Psychiatry. Published April 17, 2012. Full article