On September 22, 1930, Mother Mary Stanislaus set a challenge for the novice nuns in her congregation. The young women were a few weeks away from taking their final vows and the Mother Superior wanted each of them to write an autobiography of their lives up to that point. The sisters were to write about everything: their parents, their school years, their motives for choosing a religious life, and any “outstanding events” they’d experienced. Most importantly, the novices were to be brief: They were granted only a single sheet of paper.

The stories they told were similar in broad strokes, but the ways they told them were startlingly different. Some wrote terse, densely factual accounts of their childhoods. Others were more ebullient — inspired, even. “God started my life off well by bestowing upon me a grace of inestimable value … now I look forward with eager joy to receiving the Holy Habit of Our Lady,” wrote one. Between 1930 and 1943, hundreds of young women who joined the School Sisters of Notre Dame completed the same exercise, adding their own single-sheet autobiographies to the congregation’s archives.

More than 50 years after they were written, those stories turned out to be of great interest to researchers at the University of Minnesota. The scientists were studying aging, and the School Sisters of Notre Dame were the ideal subjects for the sort of longitudinal analysis required to understand the factors that might influence longevity and Alzheimer’s: The nuns lived abstemious lives, they rarely smoked or drank, they were easy to contact, and — crucially — they kept impeccable records. Most remarkably of all, from a research perspective, the nuns who enrolled also agreed to donate their brains upon their deaths, so researchers might better understand what life factors lead to the development of Alzheimer’s and other forms of dementia.

Those handwritten autobiographies revealed something that no brain dissection could uncover. Nuns whose autobiographies were filled with positive content — like the exuberant sister above — tended to live longer than their peers who wrote in more indifferent prose, despite the nuns living nearly identical lives from their youth on, the median age at death for the least positive sisters was 86.6, while those who wrote the most positive autobiographies had a median age at death of 93.5. A positive outlook in early adulthood, the researchers hypothesized, appeared to sustain the sisters through to the very end of life — perhaps a longer one than they might have lived otherwise.

The Minnesota Nun Study isn’t exactly a slam dunk of a paper. The sample size is small, and nuns aren’t exactly representative of the population as a whole. We don’t know if the autobiographies accurately captured the emotional state of those young women, and we can’t know for sure if a positive outlook somehow causes greater longevity, or if it’s simply correlated with it. It could be that the nuns who had healthier childhoods were more likely to write sunnier autobiographies. In other words, the usual caveats apply.

At its core, though, this study gets at something interesting that appears to apply to everyone. Having a happier childhood seems to set people up for better lives. Why this is the case isn’t totally clear, but one study of siblings found that children who were happier at age 16 had higher incomes at age 29, even when controlling for education, IQ, health, self-esteem, and later happiness. The happier children were more likely to get college degrees, be hired, and be promoted, and had higher degrees of optimism and extraversion and lower degrees of neuroticism — all factors that the study authors say influenced their later incomes. And since richer people are happier it’s likely that those adults have higher life satisfactions in their later lives, too. Many other studies find similar patterns.

Which should raise concerns about one research finding that’s begun to emerge in the past few years: Children in North America and Western Europe are currently experiencing a drop in their well-being. 

If the influence of our childhood happiness stretches well into our adult lives, this isn’t just a cause for concern in the present. It raises the prospect of a generation of less happy, less accomplished adults. But to get to grips with that, we need to know so much more about what really influences our happiness — in childhood and far beyond.

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Each year, around 100,000 people across 130 countries are asked a simple question: On a scale of 0 to 10 — with 0 being the worst possible life they can imagine and 10 being the best possible — how would they rate their current life? This simple scale was first proposed by public opinion researcher Hadley Cantril in 1965. It’s now the basis for the World Happiness Report, the biggest global life satisfaction survey, and is used to compile lists of the most and least happy countries. (Finland holds the current top spot, as it has for the last six years, while Afghanistan is bottom.)

Since 2012, these reports, which include a suite of data from the Gallup World Poll, have been the most comprehensive source of happiness data across countries and regions. The youngest people Gallup surveys are aged 15. In the past they were lumped together with older respondents. The 2024 edition is different. For the first time, it includes data from other surveys of young people to try to understand life satisfaction in children aged 10–15.

Two of those surveys, of 15-year-olds, picked up worrying signs. In most high-income Western nations, young people were less happy in 2022 than they were in 2018. And somewhat dramatically so. According to the Organisation for Economic Cooperation and Development-run Programme for International Student Assessment, between 2018 and 2022 happiness of 15-year-olds living in Western Europe dropped by 0.31. For Central and Eastern Europe it was 0.33. In Latin America it dropped by 0.63. In the Middle East and North Africa it dropped by 0.72, in South Asia by 0.46. Only East Asia bucked this trend, (and it started out with the least happy children of all the regions surveyed).

On a 0-10 scale, a shift in average national life satisfaction of between 0.3 and 0.5 represents “a very sizable change, occurring only in response to major societal shifts,” according to the OECD’s handbook on measuring subjective well-being. The OECD doesn’t give an example of what a major societal shift might be, but in the wake of the October 7, 2023, attack by Hamas, life satisfaction in Israel dropped by 0.9 points, which gives some indication of how major events shape happiness on a country level.

Of course, young people did experience a major shift between 2018 and 2022. Pretty much all of us did. But it’s not clear if the COVID-19 pandemic is the main driver here. PISA found declining life satisfaction among 15-year-olds between 2015 and 2018. The World Health Organization, which runs the other big survey of 15-year-olds, the Health Behaviour in School-Aged Children study, found that life satisfaction increased over a similar time period.

There are a number of confounders that might be messing with these results. The two surveys both measure life satisfaction on an 11-point scale, but they use slightly different wording. ¹ The PISA survey is given at the same time as a long academic test, so those lower life satisfaction scores could reflect exam pressure on the students (though we’d probably expect that pressure to be constant). The timing of the surveys might have an impact. Scottish teens, for example, showed the biggest drop in life satisfaction between 2015 and 2018 of all the countries in the PISA dataset, but that might be partly influenced by the time of sampling, which shifted from spring to autumn — meaning that the two cohorts were slightly different ages and school years, and under different amounts of exam pressure. PISA and HBSC collected their data at different points in the year and for different lengths of time, which could also skew the results.

The problems with measuring life satisfaction go beyond these two surveys. Asking people to rate their life satisfaction on a 0-to-10 scale is quick and simple. That question can be tacked onto the end of a form, and so elicit lots of responses. But those responses tend to cluster around a few values. There might also be differences in how people across countries and cultures respond to the same question.

And then there’s the question of what these questionnaires are really measuring. Life satisfaction questions ask us to judge our lives as a whole, but they don’t reveal how happy we are on a moment-by-moment basis. Psychologists call the experience of positive or negative emotions “affect,” and one way of at least approximating happiness is to sum up how someone’s affect changes throughout the day. You ask people to recall which activities they did the previous day, and how they felt about each of them. You can get even more granular and ask people to record their affect at several points during the day — an approach known as experience sampling.

Both of these methods get closer to measuring happiness as most people would understand it, and it’s possible that widespread deployment of them could reveal differences when compared to life satisfaction questions. But they’re also slow, costly, and complex to analyze, and therefore typically aren’t used for international comparisons. For now, the best tools we have are life satisfaction surveys, with all their imperfections.

The data on child life satisfaction isn’t anywhere near as comprehensive as it is for adults, says Jose Marquez, one of the authors of the World Happiness Report’s chapter on young people. But we can look to specific countries to guess at global trends. In the U.K., which is better than most at tracking the happiness of its young people, the data points to a long-established decline. In 2010–2011 children aged 10 to 15 had a mean life satisfaction of 8.21 on a 0-to-10 scale. It has declined every year since then, with the exception of 2014–2015 and 2015–2016, when it leveled off. In the latest wave, 2020–2021, average life satisfaction was at 7.62 — a huge decline (14% exactly) from its earlier levels, says Marquez. To put this into perspective, it’s as if, over the course of a decade, the average child in the U.K. went from giving their life a B to a C.

Will a generation of less happy children turn into a generation of less happy adults? Here, again, lack of good data is a problem — but there are a couple of places we can look for answers.

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The U.K. is home to a number of long-running cohort studies that have followed children into adulthood. The National Child Development Study tracks the lives of about 17,000 people born in March 1958, while the British Cohort Study follows another 17,000 people born in April 1970. Both surveys assessed a child’s intellectual development, behavior, and emotional health at the age of 16 by asking the child and their mother a set of questions. Then, as adults, the members of the two cohorts were asked to rate their life satisfaction at regular intervals.

One paper from a team affiliated with the Centre for Economic Performance at the London School of Economics examined these two cohorts to see how childhood experiences affect adult life satisfaction. If you were to go back in time to an average 16-year-old in those cohorts, you would find you could best predict their life satisfaction as an adult by looking at their emotional health — calculated by asking the child and their parents a set of questions about their mental well-being, mood, and health (questions cover, for example, worry, unhappiness, sleeplessness, bedwetting, and school avoidance). At least according to this study, adult life satisfaction is shaped to a much greater degree by early emotional life than by how they behaved or even how well they performed on cognitive tests.

Establishing causal links between childhood and adult life satisfaction is crucial but tricky, says Andrew Clark, a professor at the Paris School of Economics and one of the authors of the study into those two British cohorts. “Evaluating causality matters for policy,” he says. “If the relationship is causal, then we can invest in making children feel better at school, and that investment will pay off all the way through adulthood.”

The literature on adverse childhood experiences gives us another way to look at this link between childhood and adult life satisfaction — one that more strongly suggests that the link is causal. ACEs might include abuse, neglect, or circumstances that cause trauma or stress to children, such as living in a house where substance abuse was an issue. People who had these experiences as children are significantly more likely to have lower life satisfaction in adulthood. While that’s not evidence of causation, the dose-response relationship here gestures at it: The more ACEs reported by a child, the lower their adult life satisfaction. And there’s also some evidence using twin data — and therefore controlling for genetic predisposition — that children exposed to ACEs are more likely to have adult psychiatric disorders. In other words, it’s not just that naturally happier kids turn into happier adults. The combined evidence suggests that childhood is a critical window that shapes adult flourishing.

Even without a causal link established, these consistent dips in childhood well-being across a range of Western countries should give us pause. It’s bad enough that children feel less happy than their predecessors, and it’s plausible that this generation of unhappy children will grow into a generation of unhappy adults. All of that happiness — right now and in their future lives — is potentially at stake, and if we want to improve things then we’re better off intervening early on.

For a long time, well-being in children has been overlooked, Marquez says. Adults (and parents) have typically been more interested in whether young people end up doing well at school and finding employment. Childhood was something to be endured as long as you ended up in a decent job. To some extent, the design of Western school systems bear this out. We can look at school rankings, which often only take into account education and achievement-related metrics: student-teacher ratios, funding per pupil, achievement on tests, and college readiness. But if childhood well-being echoes throughout our adult lives, then making children happier while they’re still young should be even more of a priority. 

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When he was conducting the study, Clark worried that his research might make the whole idea of adult life satisfaction somewhat moot: your entire adult life explained by your life as a teenager, your teenage life explained by your childhood, and your childhood explained by your family life — all the way back. 

“As it turns out, that’s not the case. The child does predict the adult, but also other things that happen to the adult continue to affect their well-being,” Clark says. Mental health has a huge impact on adult well-being. So does unemployment and being in a relationship. 

What is curious, however, is how seemingly significant life events seem to have little impact on our long-term happiness. In 2006 Clark and some colleagues looked at data from a long-running household survey in Germany to figure out whether six life events — marriage, divorce, widowhood, the birth of child, getting laid off, and unemployment — have a long-lasting impact on happiness.

Divorce, widowhood, and layoffs tend to ding life satisfaction in the short term, but on average people return to their previous levels of happiness. Similarly, the birth of one’s first child doesn’t appear to have any long-term impact on happiness in either direction, and marriage only makes you happier for a couple of years. Of the six life events Clark and his colleagues studied, the only thing people didn’t adjust to was unemployment. Unemployment — particularly for men — led to sustained declines in life satisfaction.

“We’re starting to get an idea of what a life looks like” in terms of life satisfaction, says Clark. At least when it comes to middle-aged Germans. “We’re kind of rubbish on everyone else.”

The idea that individuals tend to return to a baseline level of happiness is called the “hedonic treadmill” — a concept popularized by a 1978 paper concluding that lottery winners were not happier than their less lucky neighbors. But later studies have found that winning the lottery really does make people happier, and being unemployed or in poor mental health really does make people much less happy. It might be the case that the hedonic treadmill applies to some situations but not others — if that’s true then it makes sense that we should be searching for early interventions that might boost the speed setting on our hedonic treadmills before they become calcified in adult life.

Of course, the search for interventions means we should try to understand what is causing this dip in childhood well-being in the first place. In his new book The Anxious Generation Jonathan Haidt points to rising rates of mental illness and emergency room admission rates for self-harm since around 2010 as evidence of what he calls a “surge of suffering” in young people across the anglophone world. 

Haidt marks 2010 as the start of what he called “the great rewiring” — a period where the ubiquity of smartphones and social media led to a big increase in youth mental illness. His rough argument is that “phone-based childhood” causes youth mental illness by disrupting normal neural development during puberty: depriving kids of social connections and sleep, fragmenting their attention, and addicting them to harmful platforms. Haidt’s critics, meanwhile, argue that there aren’t sufficient studies showing a causal link between smartphones and child mental health, even if the correlation is suggestive.

Although the causal picture is still unclear, we have enough evidence of a mental health downturn across such a wide spread of countries that we have lots of opportunities to experiment with different interventions. Some of those will be versions of what Haidt has suggested, such as phone-free schools and tighter age restrictions on social media apps. But there are lots of other things to try, too.

Marquez is part of a project based in Manchester called #BeeWell that is running an ongoing study tracking the factors that influence children’s well-being. The project was started after the OECD data revealed the long decline in childhood well-being in the U.K. “It is about collecting data on well-being and doing it right,” Marquez says, by talking to young people and asking them what drives their well-being. Initial results from the #BeeWell study indicate that life satisfaction is particularly low in gay and lesbian young people — there’s a bigger gap between them and heterosexual youth than between girls and boys.

In 2021 the U.K.-based charity the Early Intervention Foundation published a systematic review of school-based interventions to improve adolescent mental health. They found short-term positive effects for universal cognitive behavioral therapy as well as lessons where young people learn how to manage social interactions and manage their emotions. The evidence on mindfulness, meanwhile, is much more mixed. Doing lots more of these experiments with all kinds of interventions and joining them up with good well-being data is one way that we can start to figure out what might arrest this decline in child life satisfaction.

Lots of these experiments can be carried out at the school level, but there also might be lessons to learn from the countries where young people are doing particularly well. Lithuania jumped into the top 20 happiest countries in the latest World Happiness Report, but for people under 30 it took first place. Marquez said that Western countries might want to look more closely at Central and Eastern Europe, which used to lag behind the rest of Europe in the happiness rankings but have now caught up. “These are not such different countries from Western Europe or North America,” says Marquez. Young people there still use social media and smartphones, but they’re significantly happier than they were in 2010. 

On The Happiness Lab podcast, one of Marquez’s coauthors, Jan-Emmanuel De Neve, said that Eastern Europe might have lessons for the rest of the world. The children growing up in Lithuania have a lot to look forward to: While their parents struggled under the USSR, the country is starting to see the benefits of 20 years of EU membership, incomes are rising, and — perhaps most crucially — optimism is high. It’s possible that young people in Lithuania look around them and feel better about their life than their peers in North America and Western Europe. Unfortunately, observable economic progress and a mood of national optimism are difficult to replicate. 

The stakes here are high. We don’t have incontrovertible evidence for any explanation of what’s making kids less happy. What we do have is a strong reason to believe that young people across the Western world are collectively appreciably more miserable than they were just a few years ago. In aggregate, this trend matters for tens of millions of children now, and possibly for the rest of their lives. We should certainly commission more studies — but we shouldn’t wait for them before we try to find a way to fix things. We should try many different approaches and be prepared to scale up what works and drop what seems to have no effect. Future generations will thank us.