Scientists find connection between DNA region and depression

Scientists from King's College London in the United Kingdom have found a 'glitch' in human deoxyribonucleic acid (DNA) that may increase people's chances of suffering from depression. This was one of two independent studies targeting the link between genes and depression. The results, published in the American Journal of Psychiatry, could help researchers develop better treatments to fight this debilitating disorder.

Experts say 2 in 10 people suffer from major depression at some point during their lives. Past research on families provided insight on how genetics play a crucial role in depression. This latest King's College London study, as well as research conducted at the Washington University School of Medicine in St. Louis, United States, identified a DNA region containing up to 90 genes.

The King's College London team evaluated over 800 families in the United Kingdom that suffer from recurrent depression. The Washington University team assessed 25 families from Finland and 91 families in Australia. The researchers point out that at least two siblings in each family had a history of depression; the US group says the Finns and Australians were studied initially because they were heavy smokers.

Commenting on the results, Dr Gerome Breen, lead author of the King's College London study, says: "These findings are truly exciting. 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."

Although the data sets for the two studies were collected for different purposes and assessed in different ways, the researchers identified a 'linkage peak' on chromosome 3, which means that the depressed siblings in the families in both studies carried a number of the same genetic variations in that specific DNA region.

What is unique about these findings is that this specific DNA region has genome-wide significance, according to the researchers. Despite the fact that neither the British nor the American groups isolated a gene or genes linked to a greater risk of depression, the linkage peak is located on part of the chromosome that experts say houses the metabotropic glutamate receptor 7 gene (GRM7). Suggestive links have been found between major depression and parts of GRM7.

"Our linkage findings highlight a broad area," explains Professor Michele L. Pergadia, the lead author of the Washington University study. "I think we're just beginning to make our way through the maze of influences on depression."

Professor Pergadia says it would be a good idea to combine the studies' data sets to determine if this region of chromosome 3 continues to have a key effect.

For his part, Dr Peter McGuffin, the head of the Medical Research Council Social, Genetic and Development Psychiatry Centre at King's College London, says the findings of both studies help fuel our understanding of the connection between genes and depression.

"The findings are groundbreaking," says Dr McGuffin, a senior author of the King's College London study. "However, they still only account for a small proportion of the genetic risk for depression. More and larger studies will be required to find the other parts of the genome involved."

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