A report published by the UN on Saturday, ahead of Sunday's International Day of Happiness, found that Afghanistan came last out of 149 countries examined in the survey.
The annual World Happiness report produces its scores based on data from over three years, meaning that the low score for Afghanistan was not a result of the Taliban's return to power last year.
Lebanon, Botswana, Rwanda and Zimbabwe rounded out the bottom five least happy countries.
The other end of the spectrum was filled with the usual suspects. Finland ranked happiest for the fourth year in a row, with Denmark, Switzerland, Iceland and the Netherlands following up. Germany came 14th place.
Billions invested with little result
The poor showing for Afghanistan is another condemnation of the US-led invasion and twenty-year occupation of the central Asian country.
Despite the billions invested by the international community — with US investment alone reaching $145 billion (€131 billion at today's rate) over the two decades — the country has little to show for it.
The World Happiness report calculated its index for happiness based on six categories: GDP per capita, social support, healthy life expectancy at birth, freedom to make life choices, generosity within the population and perceptions of corruption, ranking them from zero to ten.
Afghanistan scored low in all categories — without taking into account the return of the hardline conservative Taliban regime — for a grand total of 2.5 on the scale, compared to Finland's 7.8.
Happiness score could fall even lower
Corruption was rife under the US-backed governments in Kabul, with people facing poverty and a lack of job opportunities.
While people had been hopeful after the fall of the Taliban in 2001, a Gallup poll in 2018 showed that the majority of people had no hope for the future.
"Unfortunately, the only focus was on the war, the warlords and the corrupt politicians,'' analyst Nasratullah Haqpal told the AP news agency, referring to the aftermath of the US-led invasion.
"People just became poorer and poorer and more disappointed and more unhappy... that is why these 20 years of investment in Afghanistan collapsed in just 11 days," he added, alluding to the Taliban's takeover of Kabul in August last year.
The UN report warns that the country's happiness score may fall further still due to the ongoing humanitarian crisis caused by the cessation of aid into the country following the Taliban's return to power.
ab/dj (AP, dpa)