The 2018 World Happiness Report highlighted a steady decline in the United States ranking. It has slipped to 18th place, five places down in 2016.
The top four places are taken by Nordic nations, with Finland followed by Norway, Denmark and Iceland.
"Finland has vaulted from fifth place to the top of the rankings this year," said the report's authors, although they noted that the other three Nordic countries (plus Switzerland) have almost interchangeable scores.
East African nations are among the unhappiest places in the world.
Long-hit by civil wars, ethnic cleansing and coup attempts, East African country Burundi is the unhappiest place in the world.
There are five other nations - Rwanda, Yemen, Tanzania, South Sudan and the Central African Republic - which report happiness levels below that of even Syria.
The report, an annual publication from the UN Sustainable Development Solutions Network, said all the Nordic countries scored highly on income, healthy life expectancy, social support, freedom, trust and generosity. (ANI)