Susceptibility to major depression is associated with lower life satisfaction — and this connection may be further linked to genetic makeup.
That is the finding of a new twin study from the Norwegian Institute of Public Health in connection with the University of Oslo.
For the study, researchers compared information between identical and fraternal twins to see whether having a vulnerability to major depression is linked to overall lifetime satisfaction.
Their findings show that both men and women who met the criteria for lifetime major depression (15.8 percent and 11.1 percent respectively) experienced lower life satisfaction.
Specifically, 74 percent of the relationship between major depression and life satisfaction could be explained by genes, researchers said, with the remaining association (26 percent) triggered by other environmental factors.
The researchers then analyzed the heritability of overall life satisfaction and major depression separately.
The heritability of life satisfaction, which has not been previously reported, was estimated to be 72 percent.
In other words, according to this study, the researchers believe that genes are largely responsible for manifesting the different tendencies in people to be satisfied or discontent with their lives.
The results refer to the combined effects of many genes and do not offer information regarding the effects of specific genes. The measure is also based on populations, not individuals.
Major depression had a heritability of 34 percent, which is highly consistent with prior studies. The illness is characterized by a long-lasting low mood or marked loss of interest or pleasure in all or nearly all activities.
“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,” said researcher Ragnhild Bang Nes, Ph.D.
The results suggest that genes involved in satisfaction and positivity can protect against major depression.
The study was recently published in the Journal of Affective Disorders.
Source: Journal of Affective Disorders