Researchers have discovered a DNA region on chromosome 3 up to 90 genes that appears to be linked to depression.
Senior investigator Pamela A. F. Madden, professor of psychiatry at Washington University Madden and other researchers believe it is likely that many genes are involved in depression. While the new findings won't benefit patients immediately, the discovery is an important step toward understanding what may be happening at the genetic and molecular levels, she said.
The group at King's College London followed more than 800 families in the United Kingdom affected by recurrent depression. The Washington University group gathered data from 91 families in Australia and another 25 families in Finland. At least two siblings in each family had a history of depression, but the Australian and Finnish participants were studied originally because they were heavy smokers.
"Major depression is more common in smokers, with lifetime reports as high as 60 percent in smokers seeking treatment," said lead author Michele L. Pergadia, research assistant professor of psychiatry at Washington University.
"Smokers with depression tend to experience more nicotine withdrawal and may be more likely to relapse when trying to quit. Previous studies suggest that smoking and depression run together in families. In our study, we detected a region of the genome that travels with depression in families of smokers," added Pergadia.
Meanwhile, the group in England was concerned primarily with recurrent depression. Although some of the families in the King's College London survey may have included heavy smokers, the researchers were primarily interested in people who were depressed.
"These findings are truly exciting," said Gerome Breen, lead author of the King's College London study.
"For the first time, we have found a genetic region associated with depression, and what makes the findings striking is the similarity of the results between our studies," added Breen.
From two different data sets, gathered for different purposes and studied in different ways, the research teams found what is known as a linkage peak on chromosome 3. That means that the depressed siblings in the families in both studies carried many of the same genetic variations in that particular DNA region.
The results are published in the American Journal of Psychiatry.