NZ study links gene to risk of depression

By REBECCA WALSH health reporter

Researchers have discovered differences in a gene which indicate that some people are better protected against depression despite suffering more stress than others.

The findings, published in the international journal Science, could eventually be used to develop a diagnostic test to work out who is most vulnerable to depression, which affects an estimated 10 per cent of the population.

An international team consisting of researchers from Otago University, King's College in London and the University of Wisconsin followed 847 New Zealanders in a 30-year study.

They wanted to work out why some people who suffer stressful life events, such as the death of a family member, a job loss or a relationship break-up, were vulnerable to depression but others coped well.

The findings follow work by the researchers last year which showed that a gene controlling an enzyme in the brain, when combined with a history of childhood maltreatment, was an effective indicator of future anti-social behaviour in males.

The latest results found that people who had the "long" version of a gene that helps control the brain's neurotransmitter, serotonin, were protected against stress. Those with the "short" version were more at risk of depression.

Serotonin is a brain chemical that regulates mood, emotion, sleep, appetite, memory and sexual behaviour.

Associate Professor Richie Poulton, of Otago University and one of the authors of the report, said the study focused on participants who had experienced multiple stressful life events. It found that among those with the stress-sensitive version of the gene, 43 per cent developed depression compared to 17 per cent of those with the other version.

Those with the stress-sensitive gene were also more likely to think about or attempt suicide.

Some of the study participants had been maltreated as children but whether they became depressed adults depended on whether they carried the stress-sensitive version.

Professor Poulton, director of Dunedin's Multidisciplinary Health and Development Research Unit, described the findings as groundbreaking. Previous research had largely ignored or played down the relevance of life experience.

'This study highlights that it is 'nature via nurture', which is actually taking place. It is never simply one or the other," he said.

"Environmental events or life experiences, what happens as you are growing up, these experiences effectively turn genes on and off."

The gene by itself was not enough to base a diagnostic test on.

More research to replicate the findings was needed but then it may be possible to test who was more vulnerable to depression. It could also lead to more effective medication.

Alison Taylor, chief executive of the Mental Health Foundation, said the research was significant internationally and was another step towards understanding the complexities of depression.

But there was a danger that people would expect genetic research to lead to a screening test and new drugs to "solve the problem".

The problem

* Depression is defined by the American Psychiatric Association as a period of at least two weeks in the past year when a person constantly experiences a sad, depressed mood or loss of pleasure or interest in activities.

* In the year to September 2002, 710,449 prescriptions for anti-depressants costing $29.5 million were recorded by Pharmac, the Government's drug funding agency.

* The World Health Organisation predicts that by 2020, depression will be the second leading disease burden in the developed world, after heart disease.