Nordic countries with strong social welfare structures fared best, as they have in previous years, on the United Nation's annual accounting of global happiness—while the United States finished in 18th place, down four spots from 2017.

Finland was ranked number one on the World Happiness Report, compiled by the UN Sustainable Development Solutions Network. The country was joined by other Scandinavian nations—Norway, Denmark, and Iceland—in the top four, followed by Switzerland, the Netherlands, Canada, New Zealand, Sweden, and Australia.

"The trends are not good, and the comparative position of the U.S. relative to other high-income countries is nothing short of alarming." —Jeffrey D. Sachs, editor, World Happiness Report

"I think there really is a deep and very unsettling signal coming through that U.S. society is in many ways under profound stress, even though the economy by traditional measures is doing fine," Jeffrey D. Sachs, an editor of the report, told the New York Times. "The trends are not good, and the comparative position of the U.S. relative to other high-income countries is nothing short of alarming."

The drop followed President Donald Trump's first year in office, during which the majority of Americans reported disapproval of the country's top elected official, and hundreds of thousands protested his regressive policies on immigration, women's reproductive rights, and gun control—as well as widespread concerns that the president is blatantly profiting off his position in public office.

The past year also saw reports of America's widening wealth gap, with the average upper middle-class household holding 75 times more wealth than low-income families.

Trump's tax law, pushed through Congress despite the disapproval of 53 percent of Americans, only heightened the perception of many people that the government is intent on transferring wealth to the richest Americans while the majority live paycheck to paycheck.

The World Happiness Report ranks countries according to per capita GDP, social support, life expectancy, freedom to make life choices, generosity, and corruption levels.

Life expectancy in the U.S. dropped for the second year in a row in 2017, with researchers suggesting that the opioid addiction epidemic and inequality are related to the decline.

Reigning political ideologies in the highest-ranking nations contrast sharply with that of the U.S., noted the researchers.

The countries in the top 10 tend to "believe that what makes people happy is solid social support systems, good public services, and even paying a significant amount in taxes for that," said Sachs.

Every top-ranking country also ensures that every citizen has access to free or affordable healthcare, while millions of Americans remain uninsured despite the implementation of the Affordable Care Act.