The researchers looked in these animals at a type of molecule called a transcript, which is an intermediate molecule between a gene and its corresponding protein. Differences in the level of transcripts indicate changes in gene expression.
They found 11 transcripts that were different in the blood and brain of animals that were bred to be in a perpetual state of depression compared to normal animals. In addition, they found 15 transcripts that increased or decreased in groups of rats with environment-induced depression.
Altogether the changes that the researchers found were in genes that were "most unexpected," Redei said, adding that, "This just characterized how little we know about depression."
The discovery of these biomarkers gives researchers a new list of targets to pursue as potential antidepressants, Redei said.
Having a reliable blood-based diagnostic for depression could also open the door to treating people before symptoms appear, Preskorn said. "You might want to look at high-risk populations, like if you have a family history of depression."
This approach is similar to how doctors manage other conditions like heart disease, Preskorn said. "If you know that a person has high cholesterol and high lipids, then you don't wait till the person develops atherosclerosis to start the statin drug."
You can learn more about diagnosing depression at the U.S. National Institute of Mental Health.
SOURCES: Eva Redei, Ph.D., professor, psychiatry and behavioral sciences, Northwestern Medicine, Chicago; Sheldon Preskorn, M.D., professor, psychiatry, University of Kansas-Wichita School of Medicine and chief scientific officer, clinical trial unit, University of Kansas Medical Center; April 17, 2012, Translational Psychiatry
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