Danes are happiest in the world because of their DNA
They are officially the happiest people on Earth and now scientists think they know why life is such a dream for the Danes.
The key to unbridled contentment appears to be Danish DNA. Researchers who looked at survey data from 131 countries found that the closer a nation was genetically to the Danes, the happier its people were.
Danish birth was also associated with specific versions of a gene that influences brain levels of the mood chemical serotonin.
Compared with people from other countries, Danes were less likely to possess a short version of the gene linked to low levels of life satisfaction.
Economist Dr Eugenio Proto, from the University of Warwick's Centre for Competitive Advantage in the Global Economy (Cage), said: "We looked at existing research which suggested that the long and short variants of this gene are correlated with different probabilities of clinical depression, although this link is still highly debated.
"The short version has been associated with higher scores on neuroticism and lower life satisfaction. Intriguingly, among the 30 nations included in the study, it is Denmark and the Netherlands that appear to have the lowest percentage of people with this short version."
Serotonin is a neurotransmitter that helps to relay nerve signals. A deficiency of the chemical in the brain is strongly linked to depression while levels are boosted by the drug Ecstasy. Further evidence suggested that happiness can spread between continents in immigrant genes.
Co-author Professor Andrew Oswald said: "The evidence revealed that there is an unexplained positive correlation between the happiness today of some nations and the observed happiness of Americans whose ancestors came from these nations, even after controlling for personal income and religion.
Last year's World Happiness Report from the UN ranked Denmark the happiest nation on Earth, with an average life satisfaction score of 7.69 out of 10. It was followed by four other northern European countries, Norway, the Netherlands, Switzerland and Sweden.
Ireland was ranked 18th, with the UK 22nd on the list of 156 countries.