Happiness is in your genes it seems, according to research that shows the more people in a country who have a particularly gene, the happier the nation will be.

一项研究发现可能存在幸福基因，国家的居民拥有的这种特殊基因越多，他们就会越幸福。

The DNA in question, the FAAH gene, makes a protein that affects feelings of pleasure and pain. People with a particular version of it tend to be cheerier souls.

However, wealth and health were found to have little effect on happiness. The researchers said the find could help explain why some of the world's poorest nations are also the happiest.

The team from Bulgaria and Hong Kong looked at whether there was a link between levels of the FAAH gene in a population and number of people who said they were 'very happy' in global study of life satisfaction.

Sweden - one of the happiest countries in Europe and in the world - also had lots of happy DNA. Some 26.3 percent of Swedes have the happiness gene, compared to 23 percent of Britons, 21 percent of the French and 20 percent of Germans.

The happiness gene is even rarer in southern Europe, where it is found in 18 per cent of Greeks and just 12 percent of Italians.

Further afield, Ghana, Nigeria, Mexico and Columbia all came out near the top in the happiness league - and sported high rates of the gene.

In contrast, the peoples of Iraq, Jordan, China were among the least likely to rate themselves as 'very happy' and also had the lowest levels of the gene.

But the gene and an optimistic outlook didn't always go hand in hand.

For instance, Russians and Estonians score very low on happiness, despite having the 'right' DNA, the Journal of Happiness Studies reports.