About half of us are more vulnerable to depression. When people with the short "serotonin gene" experience stressful life events, the chances of developing depression increase.

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This is the conclusion from a doctoral dissertation by Rune Jonassen at the Department of Psychology at the University of Oslo. 

More than half of the population carries the short "serotonin gene", while depression is not as widespread.

Jonassen explains the interplay between genes and environmental factors.


Genetic vulnerability + stressful events in life = depression

The short gene is associated with depression and thus implies a vulnerability. In collaboration with the gene, there are environmental factors that can either be positive and protective, or negative and dangerous.

The stressful life event is one such environmental factor that increases the risk of depression. The event is a negative factor on top of the short gene. Two negative factors, a gene and a stressful event in life, can thus lead to depression.


Protective factors may counteract the risk

On the other hand, positive environmental factors, such as a good working environment or a protective family, can counteract the development of depression, Jonassen explains.

Thus, the doctoral dissertation provides confirmation that some of us are more genetically vulnerable to depression than others.