Gene influences risk of depression

A single gene influences whether people become deeply depressed in traumas such as bereavement or emerge relatively unscathed, researchers have found.

The gene helps to regulate serotonin, the chemical that controls feelings of happiness, and by locating it scientists believe they have proved that depression is an inevitable part of life for many people.

"Those who are vulnerable don't have a rare defect or mutation,'' said Professor Terrie Moffitt of the Institute of Psychiatry at King's College London, one of the lead authors of the research. "It's a variation, like eye colour."

There are two versions of the gene, called 5-HTT, which makes a "helper'' that helps transport serotonin from one neuron to another. One version makes a short version of the helper, the other a longer one.

A study of depression among 847 people in New Zealand aged between 21 and 26 - the age when new cases of depression peak - found that 17 per cent had two copies of the "short" gene, making them more prone to depression, while 31 per cent had a pair of the more protective "long" genes. Genetic difference is not an exact predictor, but it is a guide.

Among those with two "short" 5-HTT genes, 43 per cent became depressed after stressful events. Of those with two "long'' copies, only 17 per cent became depressed.

Professor Moffitt said that the technique could usefully be used by other "gene hunters". Instead of discovering a gene and trying to find out what it does, the team studied a large group, found the common aspects between its members and carried out genetic testing.

Experts said the study, reported today in Science, is the first time that a direct genetic link has been proved between emotionally distressing events and depression.

"It is a very important discovery and a real advance for the field,'' said Dr Thomas Insel, director of the National Institute of Mental Health in Bethesda, Maryland.