A study of nearly 1000 pairs of identical and non-identical twins found genes control half the personality traits that make people happy while factors such as relationships, health and careers are responsible for the rest of our well-being.
"We found that around half the differences in happiness were genetic," said Tim Bates, a researcher at the University of Edinburgh who led the study. "It is really quite surprising."
The researchers asked the volunteers – ranging in age from 25 to 75 – a series of questions about their personality, how much they worried and how satisfied they were with their lives.
Because identical twins share the same genes and fraternal twins do not, the researchers could identify common genes that result in certain personality traits and predispose people to happiness.
People who are sociable, active, stable, hardworking and conscientious tend to be happier, the researchers reported in the journal Psychological Science.
"What this study showed was that the identical twins in a family were very similar in personality and in well-being, and by contrast, the fraternal twins were only around half as similar," Bates said. "That strongly implicates genes."
The findings are an important piece of the puzzle for researchers trying to better understand depression and what makes different people happy or unhappy, Bates said.
People with positive inherited personality traits may, in effect, also have a reserve of happiness to draw on in stressful times, he said.
"An important implication is that personality traits of being outgoing, calm and reliable provide a resource, we called it ’affective reserve,’ that drives future happiness" Bates said.