Depression is predictable

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

Depression. A vulnerability gene and a stressful life event are a combination of inheritance and environment which can trigger clinical depression.

Photo: Colourbox

Researchers have long tried to understand how this 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 life events the chances for the development of clinical depression increase.

The emotions take over

PhD candidate Rune Jonassen at the Department of Psychology, the University of Oslo has studied this interaction between inheritance and environment during work with his doctoral thesis.

He investigated how research subjects with the short variant of the gene reacted to tasks which became progressively more and more difficult and found that they had difficulties keeping track of their sensory impressions.

“Compare this with stressful occurrences in your life; your life becomes harder and you are exposed to greater and greater stress. How would your brain react to this?”

“Those who carried 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 taken as the tasks were carried out 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 tells.

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


Rune Jonassen
has studied how depression arises. Photo: Svein Harald Milde/ Dept. of Psychology

“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 such environmental factor which increases the risk of depression. Events are a negative factor on top of the short gene. Two negative factors, a gene and a stressful occurrence in life, can therefore lead to depression.

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

“Genes and environment hang together in a complicated interaction between development, learning and ageing”

This article was also in Science Nordic

By information advisor Svein Harald Milde
Published Oct. 10, 2012 9:15 AM - Last modified Nov. 1, 2012 4:29 PM