Young people, men and people in "individualistic" societies report higher levels of loneliness, according to a large-scale global study.
The study - based on responses from more than 46,000 participants around the world - is the first published research to come from the BBC Loneliness Experiment.
The ages of participants ranged from 16-99, and the results show a steady decrease in loneliness as people age.
Based on the findings, a young man living in an individualistic society - such as the UK or the US - is more likely to report feeling lonely than an older woman in a collectivist society - such as China or Brazil.
The study was carried out by Exeter, Manchester and Brunel universities.
"Contrary to what people may expect, loneliness is not a predicament unique to older people," said Professor Manuela Barreto, of the University of Exeter.
"In fact, younger people report greater feelings of loneliness.
"Since loneliness stems from the sense that one's social connections are not as good as desired, this might be due to the different expectations younger and older people hold.
"The age pattern we discovered seems to hold across many countries and cultures."
Professor Pamela Qualter, from the University of Manchester, said: "With regard to gender, the existing evidence is mixed.
"There is an awareness that admitting to feeling 'lonely' can be especially stigmatising for men.
"However, when this word is not used in the measures, men sometimes report more loneliness than women. This is indeed what we found."
Using survey responses from 237 countries, islands and territories, the researchers were able to carry out an unprecedented analysis of cultural differences.
"This is particularly important because evidence for cultural differences in loneliness is very mixed and culture can affect actual and desired social interactions in opposite directions," said Professor Barreto.
"In addition, it can be argued that admitting to feeling lonely is also more stigmatising in individualistic societies, where people are expected to be self-reliant and autonomous.
"Again, our use of a measure that did not directly refer to loneliness allowed us to show that people living in more individualistic societies report more loneliness than people living in more collectivist societies."
In light of the COVID-19 pandemic, Professor Barreto said particular attention should be paid to how social changes might be affecting young people.
"Though it is true that younger people are better able to use technology to access social relationships, it is also known than when this is done as a replacement - rather than an extension - of those relationships, it does not mitigate loneliness," she said.
The paper, published in the journal Personality and Individual Differences, is entitled: "Loneliness around the world: Age, gender, and cultural differences in loneliness."
Personality and Individual Differences