THURSDAY, Feb. 1 (HealthDay News) -- Depression may spring, at least in part, from genes on a specific region of chromosome 15, according to new findings from a team of U.S. researchers.

The findings, appearing in two papers, are being made available to other researchers around the world in the hopes of spurring more investigation and, eventually, therapies that might fight depression.

"We should be able to hone more finely into the gene," said Myrna Weissman, co-author of one of the papers and a professor of psychiatry and epidemiology at Columbia University and head of clinical and genetic epidemiology at New York State Psychiatric Institute, both in New York City. "Then, we can see mutations and develop treatments," she said.

The research is being published in the February issue of the American Journal of Psychiatry and was led by scientists at Stanford University.

According to background information in the papers, about 10 percent to 15 percent of people suffer from severe depression at some point in their lives, and 3 percent to 5 percent have recurrent episodes. Women are twice as likely as men to become depressed.

Studies of families and twins have also revealed that depression is partly a disease of genetics, although no one gene is thought to be responsible. Instead, several genes may be interacting to increase a person's risk. Environmental factors, including psychological trauma, may then tip a person over the edge, so to speak.

Finding specific genes involved in the process is critical, because then, researchers could decipher exactly what the genes do and how they're involved in depression. Therein may lie important clues for treatment.

This would also help scientists understand the environmental factors that can trigger depression, they said.

In one study, researchers examined 631 families in which at least two members had had repeated episodes of severe depression that began in childhood or early adulthood.

"Based on extensive data that shows that the most familial form of depression is that which begins before the age of 30, and which involves recurrent episodes, we went after a sample of people where at least one family member had this kind of a depression, and they had a sibling who had a similar depression," Weissman explained.

Participants were recruited from all over the country, and were primarily of European ancestry.

The first study involved a scan of the entire genome to look for "linkages" between depression and DNA markers. This effort identified several chromosome regions that looked promising for more research.

The second study involved a more in-depth analysis of the most "suspicious" of these regions (on chromosome 15). All told, 94 DNA markers were studied (in both papers) and revealed significant evidence for linkage to depression.

"This is a very significant finding. This is a more refined map of earlier findings from this group," said Dr. Ma-Li Wong, a professor of psychiatry and vice chairwoman for translational research at the University of Miami Miller School of Medicine. "Susceptibility to depression seems to be related to this chromosome, and we don't know which genes will be implicated, but hopefully through the continuation of this line of work, we will find out."

The next phase of the research will delve even more deeply into the genetics of 2,000 individuals, the researchers said.

More information

The research team is still recruiting for additional studies. Visit Stanford University for more information.