An article from University of Oslo

A vulnerability gene combined with a stressful event can trigger clinical depression. (Photo: Colourbox)

Depression is predictable

Why are some people more vulnerable to depression than others? The short variant of a gene combined with stressful events may trigger a depressive episode.

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University of Oslo

The University of Oslo is Norway's leading institution of research and higher education.

Researchers have for a long time tried to understand how a particular gene affects our brain. It is known that the gene, which codes for the neurotransmitter serotonin, predisposes for depression.

When people with the short “serotonin gene” experience stressful events the chances for development of clinical depression increase.

The emotions take over

PhD candidate Rune Jonassen at the Department of Psychology, University of Oslo has studied the interaction between inheritance and environment.

He has looked into how people with the short variant of this gene reacted to tasks which became progressively more and more difficult. He found that they had difficulties keeping track of their sensory impressions.

Rune Jonassen has studied the origin of depression. (Photo: Svein Harald Milde/ Dept. of Psychology)

“Compare this with stressful episodes in your life; when your life becomes harder and you are exposed to more and more stress. How will your brain react to this?” asks Jonassen.

“People with the short gene had problems with working memory during the tasks we gave them. They were healthy people, but they carry a vulnerability gene”, he says.

As the research subjects solved the tasks their brains where photographed. On the pictures of brain activity Jonassen saw that people with the short gene used greater resources within their brains without doing any better on the tests.

“We saw that they used more energy in the brain structures at the front of the brain linked with task solving. Simultaneously, they made more mistakes on the tasks. The brain stressed and used a lot of energy without the research subjects doing any better. They actually performed poorer on the tasks. “

You come no further

“How the short gene is connected to higher brain functions, such as task solving or brooding has not been explored before” he explains.

In a follow-up study Jonassen looked at the connection between those brain areas which regulate our emotions and areas which perceive feelings. This connection was also weaker among those with the short variant of the gene. This can cause depressive feelings to persist and inhibit certain individuals from coming any further beyond the negative event.

“These findings make us better able to discover genetic vulnerability, before one develops depression” he says.

Individualised treatment

“Awareness of genetic vulnerability can give us a more precise diagnosis and individualised treatment of people who suffer from depression”

By individualised treatment Jonassen means different forms of psychotherapy for people who have varying genetic compositions, but with the same diagnosis.

More than half of the population carry the short “serotonin gene”, while depression is less prevalent. Jonassen explains the interaction between genetic and environmental factors.

“The short gene is associated with depression and therefore implies vulnerability. In association with this gene, environmental factors are found which can be positive and protecting, or negative and dangerous.

Not just born like that

A stressful life event is one of the environmental factors that increases the risk of depression. With two negative factors, the gene and a stressful incident, the risk is even higher.

“But positive environmental factors, such as a good working environment or a protective family counteract the development of depression”, explains Jonassen

“Genes and environment are linked in a complicated interaction between development, learning and ageing”

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