Researchers Identify DNA Region

Major depression affects approximately 20 percent of people at some point during their lives, and family studies have long suggested that depression risk is influenced by genetics. The new studies identify a DNA region containing up to 90 genes.

“What’s remarkable is that both groups found exactly the same region in two separate studies,” says senior investigator Professor Pamela A. F. Madden. “We were working independently and not collaborating on any level, but as we looked for ways to replicate our findings, the group in London contacted us to say, ‘We have the same linkage peak, and it’s significant.’”

“Major depression is more common in smokers, with lifetime reports as high as 60 percent in smokers seeking treatment,” says lead author Assistant Professor Michele L. Pergadia. “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.”

“These findings are truly exciting,” says 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.” 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.

“Our linkage findings highlight a broad area,” Pergadia says. “I think we’re just beginning to make our way through the maze of influences on depression. The U.K. samples came from families known to be affected by depression. Our samples came from heavy smokers, so one thing we might do as we move forward is try to better characterize these families, to learn more about their smoking and depression histories, in addition to all of their genetic information in this area.”; Source: Washington University School of Medicine St. Louis