Ask most people which age group carries the heaviest burden of loneliness, and they will point somewhere near retirement: an image of someone living alone, children grown and gone, old friends dying off one at a time. A 2024 study tracking two decades of Danish survey data points somewhere else entirely.
Researchers from the University of Southern Denmark and the National Institute of Public Health, publishing in the Scandinavian Journal of Public Health, analysed six waves of the Danish Health and Morbidity Surveys, run in 2000, 2005, 2010, 2013, 2017 and 2021, covering 83,437 people aged sixteen and up. Respondents answered a standard loneliness question in each wave, which is what lets the researchers compare 2021 against 2000 as the same measurement rather than two different surveys asking roughly similar things. Across that period, self-reported loneliness among men rose from 13.2 percent to 27.4 percent. Among women it rose from 18.8 percent to 33.7 percent. In both cases, that is close enough to a doubling that the word fits without much rounding.
The generation whose numbers moved the most
The overall national increase was about fourteen to fifteen percentage points. But when the researchers broke the data down by birth cohort and age, one group’s numbers moved far past that: adults aged sixteen to twenty-four saw loneliness climb by 28.4 percentage points among men and 30.7 among women, roughly double the national average shift. The published summary doesn’t spell out exactly how much each of the other age bands moved individually, but for the youngest adults alone to run at double the overall average, the remaining age groups have to be moving considerably less than that on the whole. The people usually pictured when the word “loneliness” comes up, those well into retirement, were not where this two-decade trend hit hardest.
The two decades made loneliness look like it was creeping up everywhere. It was actually concentrated in the years a life is supposed to be at its most social.
A shape that stayed the same, a size that didn’t
The old assumption about loneliness and age wasn’t entirely wrong. The study also found a U-shaped pattern across the age spectrum, most visible among women, meaning loneliness is and remains somewhat higher at both ends of adulthood than in the middle. Retirement, widowhood and declining health are still real, well-documented drivers of isolation later in life, and nothing here erases that.
Over these two decades, the basic shape of who tends to feel lonely at any given moment held steady. The youngest end of that shape simply got worse, relative to everywhere else, by a wide margin. A snapshot taken in 2000 and a snapshot taken in 2021 would still show loneliness dipping in midlife and rising at both edges. It’s the size of that rise at the youngest edge that would look unrecognisable next to the same chart from twenty years earlier.
A pandemic wave, and a trend that came before it
The final survey wave was collected in 2021, during a national COVID-19 lockdown, and the study’s authors are upfront that this likely inflated the last data point on its own. That is a real limitation, and it means some share of the jump between 2017 and 2021 belongs to a specific, unrepeatable year rather than a durable shift. But the researchers didn’t attribute the pattern to the pandemic wave alone. Their statistical breakdown found the rise was driven by what they call period and age effects, meaning something about being young during this stretch of the twenty-first century, rather than cohort effects, which would point to something distinct about a particular generation carried forward as they age.
In plain terms: it isn’t that today’s young adults will simply stay this lonely for the rest of their lives, and it isn’t a one-off pandemic artefact either. It’s tied to what being sixteen to twenty-four has actually looked like these past two decades.
Why the usual assumption misses this
Part of why this finding cuts against intuition is that so much public attention, and so much policy money, is still aimed at the older end of the curve, for understandable reasons.
What this study adds isn’t a correction to that picture so much as a second one sitting alongside it: a trend line climbing fastest among people who are, on paper, at the most socially saturated stage of life, still in school or newly out of it, theoretically surrounded by peers more than at almost any other point in adulthood.
The researchers don’t pin down a single cause, and it would overstate their findings to hand them one. What the data supports is narrower and still striking: whatever is driving Denmark’s rise in loneliness over the past twenty years, it is showing up hardest in exactly the age group least expected to carry it.
What this doesn’t settle
A study built this way has real limits. Six survey waves across two decades can establish that a change happened and roughly when it accelerated, but a repeated cross-sectional survey like this one can’t isolate a single cause the way a controlled experiment could.
Denmark isn’t the only country where researchers and public health bodies have started flagging loneliness among young adults specifically, rather than treating it as a problem that only sharpens with age, and this study doesn’t attempt to explain why the pattern would hold across a wider region even if it does.
What it does establish, carefully and with a fairly large sample, is the shape of the change inside Denmark’s own numbers: an increase spread across the adult population, hitting hardest, by a wide margin, in the years most people would least expect it.
If any of this sounds closer to home than it does like an interesting statistic, it’s worth taking seriously on its own terms. Loneliness at any age is worth talking about, whether that’s with a friend who’s easy to be honest with or a professional trained to help.