Finland remains the world's happiest country for a seventh straight year in the annual UN-sponsored World Happiness Report.
Nordic countries kept their places among the ten most cheerful, with Denmark, Iceland and Sweden trailing Finland, while Ireland finds itself in 17th place - down from 14th a year ago.
Afghanistan, plagued by a humanitarian catastrophe since the Taliban regained control in 2020, stayed at the bottom of the 143 countries surveyed.
For the first time since the report was published more than a decade ago, the United States and Germany were not among the 20 happiest nations, coming in 23rd and 24th respectively.
In turn, Costa Rica and Kuwait entered the top 20 at 12 and 13.
Director of the well-being research centre at the University of Oxford and editor of the report Jan-Emmanuel de Neve said Scandinavians dominate the top five.
"I think obviously the headlines are that Finland and Denmark still top the World Happiness Report, and the Scandinavians do dominate the top five. At the bottom, Afghanistan has slid even further in terms of low well-being.
"The average person in Afghanistan reports 1.7 on the scale from 0 to 10 in terms of life satisfaction, otherwise the quality of life as people experience it is extraordinarily low in Afghanistan. In Denmark and Finland, it's quite a bit higher, almost 8 out of 10 is the average life satisfaction in those countries."
The report noted the happiest countries no longer included any of the world's largest countries.
"In the top ten countries only the Netherlands and Australia have populations over 15 million. In the whole of the top 20, only Canada and the UK have populations over 30 million."
The sharpest decline in happiness since 2006-10 was noted in Afghanistan, Lebanon and Jordan, while the Eastern European countries Serbia, Bulgaria and Latvia reported the biggest increases.
The happiness ranking is based on individuals' self-assessed evaluations of life satisfaction, as well as GDP per capita, social support, healthy life expectancy, freedom, generosity and corruption.
Jennifer De Paola, a happiness researcher at the University of Helsinki in Finland, said that Finns' close connection to nature and healthy work-life balance were key contributors to their life satisfaction.
In addition, Finns may have a "more attainable understanding of what a successful life is", compared to for example the United States where success is often equated with financial gain, she said.
Finns' strong welfare society, trust in state authorities, low levels of corruption and free healthcare and education were also key.
"Finnish society is permeated by a sense of trust, freedom, and high level of autonomy," Ms De Paola said.
This year's report also found that younger generations were happier than their older peers in most of the world's regions - but not all.
In North America, Australia and New Zealand, happiness among groups under 30 has dropped dramatically since 2006-10, with older generations now happier than the young.
By contrast, in Central and Eastern Europe, happiness increased substantially at all ages during the same period, while in Western Europe people of all ages reported similar levels of happiness.
Happiness inequality increased in every region except Europe, which authors described as a "worrying trend".
The rise was especially distinct among the old and in Sub-Saharan Africa, reflecting inequalities in "income, education, health care, social acceptance, trust, and the presence of supportive social environments at the family, community and national levels," the authors said.
