Washington, October 26: Vulnerability to major depression is determined by how satisfied we are with our lives – and this relationship can be largely attributed to genes, researchers have suggested.
This is the main finding of a new twin study from the Norwegian Institute of Public Health in collaboration with the University of Oslo.
The researchers compared longitudinal information from identical and fraternal twins to determine how vulnerability to major depression is associated with dispositional (overall) lifetime satisfaction.
Results showed that both men and women who met the criteria for lifetime major depression (15.8 percent and 11.1 percent respectively) reported lower life satisfaction.
74 percent of the relationship between major depression and life satisfaction could be explained by genes, researchers said.
The remaining association (26 percent) could be explained by unique environmental factors.
The researchers also calculated the heritability of dispositional life satisfaction and major depression separately.
The heritability of dispositional life satisfaction, which has not previously been reported, was estimated to be 72 percent. In other words, it is largely genes that explain why we differ in our tendency to be satisfied and content with our lives.
It is a measure of how much of the individual differences in a trait or disorder can be attributed to genetics.
It refers to the combined effects of many genes and does not provide information about the effect of specific genes.
The measure is based on populations, not individuals.
Major depression had a heritability of 34 percent, which is highly consistent with previous studies.
“The stable tendency to see the bright side of life is associated with lower risk of major depression because some genetic factors influence both conditions”, says researcher Ragnhild Bang Nes from the Division of Mental Health.
Genes involved in satisfaction and positivity thus give protection against major depression.
The study was recently published in the Journal of Affective Disorders. (ANI)