Nigeria ranked 91st out of 156 countries in the annual Sustainable Development Solutions Network's (SDSN) 2018 World Happiness Report released by the United Nations on Wednesday.
The report ranked 156 countries according to factors such as GDP per capita, social support, healthy life expectancy, social freedom, generosity and absence of corruption.
The report revealed that Finland is the world's happiest country while Burundi placed at the bottom of the happiness index.
The survey also found Americans were getting less happy even as their country became richer, while Finland rose from fifth place in 2017 to oust Norway from the top spot.
In 2017, Nigeria ranked 95th on the index.
The 2018 top-10, as ever dominated by the Nordics, is Finland, Norway, Denmark, Iceland, Switzerland, Netherlands Canada, New Zealand, Sweden and Australia.
The U S. came in at 18th, down from 14th place in 2017 while Britain was 19th and the United Arab Emirates 20th.
One chapter of the 170-page report is dedicated to emerging health problems such as obesity, depression and the opioid crisis, particularly in the U. S. where the prevalence of all three has grown faster than in most other countries.
While income per capita has increased markedly in the U. S. over the last half-century, the happiness index has been hit by weakened social support networks, a rise in perception of corruption in government and business and declining confidence in public institutions.
The head of the SDSN, Jeffrey Sachs of New York's Columbia University, told Reuters that the U.S faces a social crisis as there is "more inequality, less trust, less confidence in government."
"It's pretty stark right now. The signs are not good for the U.S. It is getting richer and richer but not getting happier," he said.
Asked how the current political situation in the United States could affect future happiness reports, Sachs said: "Time will tell, but I would say that in general that when confidence in government is low, when perceptions of corruption are high, inequality is high and health conditions are worsening ... that is not conducive to good feelings."
For the first time since it was started in 2012, the report, which uses a variety of polling organisations, official figures and research methods, ranked the happiness of foreign-born immigrants in 117 countries.
Finland took top honours in that category too, giving the country a statistical double-gold status.
The foreign-born were least happy in Syria, which has been mired in civil war for seven years.