Is happiness in our genes?

It is easy to observe that some people are happier than others. But trying to explain why people differ in their happiness is quite a different story. Is our happiness the result of how well things are going for us or does it simply reflect our personality? Of course, the discussion on the exact roles of nature (gene) versus nurture (experience) is not new at all. When it comes to how we feel, however, most of us may think that our happiness must be more strongly influenced by situational factors than our genes. But could it be that some people are happier than others simply because they inherited genes that make them generally feel better regardless of whether they had a good or a bad day? In other words, could being lucky in the genetic lottery be more important for our happiness than whether we get to travel to exotic places or enjoy the company of loving friends? Fortunately, we are now able to consider this age-old debate from a scientific rather than a merely philosophical perspective. So what does science tell us about the origins of individual differences in happiness?

Much of classic research on the role of genes is based on twin studies. Rather than looking at actual molecular differences in the DNA, these studies compare similarities between identical and fraternal twins. Given that identical twin siblings are genetically more similar to each other than fraternal twins, it is possible to statistically estimate how much of the differences between people can be explained by heritable (i.e. genetic) versus environmental factors.

The first twin study that focused on people’s positive feelings reported a genetic contribution of about 40%, which means that 40% of the differences in positive emotionality between people is explained by heritable factors (i.e. differences in the degree of relatedness between people). Recently all available twin studies on happiness have been combined into one single study. The results support the original finding that on average about 40% of the differences in happiness between people is explained by genetic factors while the remaining 60% are accounted for by the environment. However, while twin studies indicate how much of the difference in happiness is explained by genetic factors, they don’t inform us about the specific genes that are involved.

Due to twin study findings, we have known for many years that happiness has a significant genetic component, but it is only recently that technological progress enabled scientists to investigate happiness on the molecular level. Many of these new studies apply a genome-wide approach. This usually includes the measurement of up to several millions of genetic differences across the whole genome. This vast molecular data can then be used to estimate the average total genetic contribution to a specific trait. When applied to well-being, it has been found that 12-18% of differences in well-being between unrelated people is explained by the combined effect of more than 500,000 common genetic variants. The identification of the specific gene variants that make up this genetic component requires very large samples which have not been available until very recently.

Earlier this year, the hitherto largest study on the genetics of happiness has been conducted with a sample of almost 300,000 people. The study was successful in identifying three different genetic variants, two in chromosome 5 and one in chromosome 20. However, these happiness-related gene variants explained less than 1% of happiness differences between people. This is a lot less than the 40% twin studies suggested. How can we explain this difference? Besides a range of methodological and technical reasons, the conflicting results between twin and molecular studies suggest that although happiness has a genetic component, it is made up of many gene variants with very small effects on happiness. In other words, there is no “happiness gene” but many thousands of gene variants that contribute to observed stable differences in happiness. The individual contribution of these variants is so small that it is extremely difficult to measure.

It is important to clarify that genes and experiences are intertwined in complex ways. For example, our genes make certain experiences more likely and experience, on the other hand, can influence the function of our genes through epigenetic mechanisms. Recent studies also suggest that our genes may influence how strongly we respond to the experiences we make. In other words, some people are characterised by a genetic sensitivity which makes them more likely to feel happy when they experience something positive compared to other people who are genetically less sensitive.

In conclusion, while experience is certainly important for our well-being, some of our happiness is indeed in our genes. However, there is no magic “happy gene” but rather thousands of gene variants, each making a tiny contribution to our happiness. Although the complex interplay between genes and experience is likely to play a central role for our happiness, this has not been investigated in great detail yet. More research is required to help us better understand the role genes play for our happiness.

Featured image credit: Joy of Life by ludi. CC0 public domain via Pixabay.