Young adults are more likely to feel lonely than older age groups, says a study from the Office for National Statistics.
The research found that almost 10% of people aged 16 to 24 were "always or often" lonely - the highest proportion of any age group.
This was more than three times higher than people aged 65 and over.
Researchers suggest that older people might become more "resilient" to worries about loneliness.
There has been growing political interest in loneliness as a significant social problem.
The prime minister earlier this year set out plans to alleviate loneliness and "social isolation" - with a warning that millions of people were suffering from a lack of regular contact with others.
The research from the ONS, based on a survey of more than 10,000 adults, found that about one in 20 people always or often felt lonely.
Although there has been much focus on the isolation of elderly people, this study found that younger adults were the most likely to report feelings of loneliness and that such feelings "tend to decrease with age".
Across all the measures and categories, the researchers say that people aged over 75 are "63 times less likely to report loneliness than those aged 16 to 24 years".
"It's possible that people become more resilient to loneliness as they get older, possibly through the experience of significant life events and life transitions," says the study.
Cal Strode, of the Mental Health Foundation, said that loneliness among young people could be driven by social media and the "digital world".
"Teens can have thousands of friends online and yet feel unsupported and isolated. Technology, including social media, could be exacerbating social isolation," he said.
Reluctant to admit loneliness
Women were consistently more likely than men to report feelings of loneliness.
But the researchers suggested this could also be influenced by a reluctance among some men to admit to the extent of their loneliness.
The study highlighted particular groups at greater risk of loneliness.
Older women who had been widowed and were living alone were particularly likely to be lonely, especially if this was exacerbated by illness.
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People who were single, middle-aged, living alone and with poor health, were identified as another peak of loneliness.
Loneliness was linked to a lack of permanence or sense of belonging - such as young renters who felt few connections to their local community.
Not about 'personality'
There were other themes that emerged - illness and unemployment made loneliness much more likely. Carers were more vulnerable to loneliness and to be cut off from friends.
The study also profiled the least likely to be lonely.
They were likely to be older, male, living with a partner, working, homeowners, well-connected with their local area and in good health.
Laura Alcock-Ferguson of the Campaign to End Loneliness said the findings showed that loneliness was not about someone's "personality", but was likely to be driven by factors such as their "health and economic status".
Izzi Seccombe, chairwoman of the Local Government Association's committee on well-being, said: "The harm loneliness can cause, both physically and mentally, can be devastating to people of all ages - it is a serious public health concern which studies suggest can be as harmful as smoking 15 cigarettes a day.
"We all need to be on the lookout for each other, which could be as simple as a quick visit to check on a neighbour, who could be a young mum without any family nearby, or an older person living alone," said Ms Seccombe, leader of Warwickshire County Council.