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.
与之相反,伊拉克,约旦和中国的居民是最不幸福的,而他们的幸福基因水平也是最低的。
But the gene and an optimistic outlook didn't always go hand in hand.
然而这种幸福基因和幸福感并不总是成正比的。
For instance, Russians and Estonians score very low on happiness, despite having the 'right' DNA, the Journal of Happiness Studies reports.
比如,《幸福研究》杂志报道,尽管俄罗斯人和爱沙尼亚人拥有足够的幸福基因,但他们的幸福得分很低。
Climatic differences were also found to be significantly associated with national differences in happiness.
研究发现,气候的不同也会在很大程度上影响到国家幸福水平。
Study co-author Michael Minkov, of the Varna University of Management, said: 'We cannot fail to notice the high occurrence of the gene in equatorial and tropical environments in the Americas and Africa - and the lower occurrence of [it] around the Mediterranean Sea than in Northern Europe.
A spokesman for the journal's publisher, Springer, said: 'Genetics is not the only determinant of happiness.
这本杂志的出版商斯普林格出版社的发言人说:“基因并不是决定幸福的唯一因素。”
'The economic and political difficulties continuously experienced by Eastern European nations contribute to the very low happiness scores of Russians and Estonians.'
东欧国家不断经历的经济和政治困难导致了俄罗斯和爱沙尼亚的幸福得分很低。
Researcher Professor Michael Minkov, of Sofia's Varna University, said that nations not blessed with the right DNA aren't necessarily destined to be miserable – happiness can still raise and fall for other reasons.