A recent paper in the Journal of Happiness Studies shows that, unsurprisingly, some of the differences in national subjective wellbeing are attributable to genetic factors. The authors found that national percentages of very happy people across the most recent World Values Surveys are consistently and highly correlated with national prevalence of the rs324420 A allele in the FAAH gene, involved in the hydrolysis of anandamide, a substance that reportedly enhances sensory pleasure and helps reduce pain. They also found that climatic differences are also significantly associated with national differences in happiness, whereas economic wealth, recent economic growth, rule of law, pathogen prevalence and the distribution of the short versus long alleles in the serotonin transporter gene SLC6A4 are not significant predictors of national happiness.
Countries with high percentages of very happy people comprise mostly northern Latin American countries, with relatively high percentages of Amerindians or people of mixed Euro-American descent, as well as West African countries. The main tribes of Nigeria—Hausa and Yoruba—are next in the ranking. The lowest prevalence of the A allele is found in some Arab and East Asian nations.
. Differences in happiness between Northern and Central or South Europeans also seem attributable to the genetic differences between them, since Northern Europeans have a much higher prevalence of the A allele. North European countries with high percentages of very happy people and high prevalences of the A allele include the UK, Sweden and the Netherlands.