Young people in the UK have some of the lowest levels of "mental wellbeing", according to an international survey.
A study of the attitudes of 15- to 21-year-olds in 20 countries examined levels of optimism, confidence and a sense of being loved.
Japan was the only country lower than the UK on this wellbeing ranking, published by the Varkey Foundation education charity.
Only 15% of young people in the UK said they got enough sleep and exercise.
The study looked at the views and expectations of so-called Generation Z, born in the years around the new millennium, based on a survey of more than 20,000 people in countries including the UK, the United States. France, Germany, India, China and Argentina.
And it suggested that there was no clear link between material wellbeing and mental health.
Fearful for the future
While the UK was almost at the bottom of the rankings for wellbeing, along with countries such as Japan and South Korea, the top places were taken by young people in Indonesia, India and Nigeria.
South Korea, with a reputation for a fiercely pressurised education system, was the only country where young people actively disliked where they lived.
Young people across this global sample, including the UK, reported that they were more pessimistic than optimistic about the future.
Although young people in China and India both bucked these gloomy expectations - with their young anticipating a more positive future.
The perception of risk from extremism, terrorism and conflict was widespread - more so than worries about climate change or inequalities between rich and poor.
In the UK, extremism and terror was identified as the biggest single reason for being "fearful for the future", followed by the threat of "conflict and war".
There were big differences in attitudes towards the principle of free speech - and whether it should be protected even for views might offend.
Only about a third of young people in Nigeria supported the right to free speech, if it was likely to offend some ethnic groups or religious beliefs.
In contrast, more than two-thirds of young people in Argentina supported free speech, regardless of who it might antagonise.
But there was a common global trend for these young people to hold broadly liberal views on issues such as migration, religious tolerance, equal rights for men and women and acceptance of same-sex marriage.
"At a time of nationalist and populist movements that focus on the differences between people, the evidence shows that young people - whatever their nationality or religion - share a strikingly similar view of the world," said Vikas Pota, chief executive of the Varkey Foundation.
"Teenagers in Nigeria, New Delhi and New York share many of same priorities, fears, ambitions and opinions.
"There is far more unity among young people than a glance at the headlines would suggest.
"Young people are passionate believers in the right to live the life that they choose, whatever their background, free of prejudice of all kinds."
But Mr Pota said that this was also a generation that was "deeply pessimistic about the future of the world".