Happiness can be elusive, both in personal life and as a scientific concept. That’s why this paper, recently published in Molecular Psychiatry, seemed so striking.
“A genome-wide association study of positive emotion identifies a genetic variant and a role for microRNAs.” Translation: a glimpse into the genetics of positive emotions.
Editorial note: Although the research team here is careful and confirms the findings in independent groups and in brain imaging and fear discrimination experiments, this is a preliminary result. More needs to be explored about how these genetic variants and others affect positive emotions.
“With relatively few studies on genetic underpinnings of positive emotions, we face the challenges of a nascent research area,” the authors write.
Perhaps ironically, the finding comes out of the Grady Trauma Project, a study of inner-city residents exposed to high rates of abuse and violence, aimed at understanding mechanisms of resilience and vulnerability in depression and PTSD.
“Resilience is a multidimensional phenomenon, and we were looking at just one aspect of it,” says first author Aliza Wingo. She worked with Kerry Ressler , now at Harvard, and Tanja Jovanovic and other members of the Grady Trauma Project team.
“Positive affect” is what the team was measuring, through responses on questionnaires. And the questions are asking for the extent that respondents feel a particular positive emotion in general, rather than that day or that week.
Two genetic variants linked to positive affect emerged from their scan of more than 2500 study participants’ genes, and they were close together on chromosome 1. One of the variants affects the activity of a nearby gene, which encodes a pair of microRNAs (181a and 181b). This relationship holds up both in the brain, using publicly available data, and the blood, with Grady Trauma Project data. Some information was already known about the biology of these microRNAs, although they seem to be involved in regulating the immune system as well as brain functions.
With a subset of study participants, the team also went on to show the effects of the chromosome 1 genetic variant on brain imaging and on fear discrimination tests (response to startle). People with the less common form of the variant showed greater responses to “positive images” via fMRI in several brain regions. An example image in the paper shows a child behaving exuberantly on a tricycle; the images come from a standard set used by psychologists.
The team also replicated their findings in another Emory group, the Center for Health Discovery and Well Being, and estimated that common genetic SNPs (the variants that are easy to study in this way) explain about 20 percent of positive affect variance. Here, the effect size estimate is a ballpark figure, because the statistical analysis was at the border of significance.
In the discussion, the authors refer to a recent Dutch genome-wide study of “subjective wellbeing, depressive symptoms and neuroticism”, which identified variants that did not overlap with those identified here. The Dutch study was larger (more than 100,000 people), but the population groups were also quite different.