Recent research published in psychological science Our results suggest that local changes in the gap between rich and poor do not significantly predict changes in depression among teenagers. Although some social theories propose that economic inequality is inherently detrimental to public mental health, our findings provide evidence that fluctuating income inequality within a given community has little practical impact on adolescent depressive symptoms.
The idea that how a society’s wealth is distributed affects its population’s well-being has received significant attention over the past few decades. The income inequality hypothesis, popularized by social scientists, proposes that widening economic inequality fosters status insecurity, undermines social trust, and reduces public services. This perspective suggests that inequality acts like an environmental pollutant, affecting everyone involved in the social landscape, regardless of their personal bank accounts.
Adolescence is a particularly sensitive time to test this idea. During this teenage period, people become highly sensitive to peer comparisons and social hierarchy. At the same time, most mental health disorders first appear during this developmental period. Rates of depression among teenagers have increased significantly in countries such as Norway, and some public health experts say rising national income inequality may be contributing to this alarming trend.
Sondre Arsene Nilsen, associate professor in the Department of Special Needs Education at the University of Oslo and senior researcher at the NORCE Norwegian Research Center’s Regional Center for Child and Adolescent Mental Health and Child Welfare, wanted to investigate this putative link. “Income inequality is often discussed as one of the key social determinants of health, and much research appears to proceed on the assumption that it is a well-established causal factor for mental health-related outcomes,” Nilsen said.
He noted that past assessments often relied on comparing unequal countries with equal countries at a given point in time. “That’s a big limitation,” Nilsen explained. “Studies like this may show that mental health tends to be worse when there is more inequality, but we don’t know whether changes in inequality actually lead to changes in mental health, which is probably the question we are most interested in.”
Comparing completely different countries makes it difficult to rule out cultural or political factors that might explain changes in depression rates. “We therefore wanted to test more directly the question of whether adolescent depression symptoms change as well as income inequality changes over time within the same municipality,” Nilsen said.
To build a more accurate picture, Nilsen and his colleagues drew on vast amounts of health and economic data from Norwegian municipalities. They analyzed a large collection of responses from Norway’s National Youth Survey Program. This program regularly surveys middle school and high school students across the country about their lifestyle, health, and well-being. The current study focuses on survey responses collected from 2010 to 2019.
The final analytic sample included approximately 550,000 adolescent respondents from 863 city years and 340 specific cities. To measure depression in teens, researchers used a widely accepted six-question self-report tool. This survey asked students to rate how often they felt affected by depressed mood in the previous week.
The authors also tracked students’ self-reported family economic status. Students rated whether their family’s financial situation had been mostly good, fair, or bad over the past two years. For the economic side of the equation, the authors calculated income inequality for each municipality in a given year based on official government register data.
They primarily used the Gini index, a standard statistical tool that measures how wealth is distributed across a population. A score of 0 represents perfect equality, with everyone earning exactly the same amount, and higher scores indicate greater inequality. To test their findings, the researchers also used a second economic indicator that directly compares the incomes of the top 10 percent of earners to the bottom 10 percent.
The researchers controlled for a variety of demographic and economic factors at both the regional and individual levels. These took into account median municipal income, local poverty rates, age, gender, and the specific year in which the survey was conducted. Taking local poverty rates into account helps separate the stress of absolute material hardship from the psychological effects of simply living near wealthy people.
Using a sophisticated statistical model that isolates specific changes occurring within a single town over time, the authors found that changes in municipal income inequality did not statistically predict overall changes in adolescent depressive symptoms. Even as the gap between rich and poor within a region widened, the average mental health of teens living there remained essentially unchanged. “Given the mixed prior literature and the results of recent high-quality studies, we thought it was quite possible that the effect would be small or non-existent,” Nilsen told SciPost.
“Perhaps what was most telling was how close to zero the effect across municipalities was, even in large studies designed to test this question directly,” he added. To test this near-zero effect, scientists employed a statistical method known as an equivalence test. Traditional statistics typically focus on finding whether an effect simply exists.
“Because the analysis was based on repeated observations of many municipalities over a long period of time, the study had sufficient power to detect small effects within municipalities,” Nilsen said. Equivalence tests helped determine whether the observed effects were within a range of predefined outcomes that would be considered too small to have any real-world impact. “So we used an equivalence test to see if the effect was large enough to actually matter,” Nilsen explained.
Equivalence tests confirmed that the overall effect of income inequality on depression is virtually negligible. The researchers also examined whether this economic change was disproportionately harming teens who were already in poor economic situations. They found no meaningful interactions. This means that adolescents from struggling families are not uniquely affected by the widening regional wealth gap compared to wealthier families.
Focusing on gender, the authors observed very small differences in the data. As regional inequality increased, depressive symptoms tended to increase slightly among teenage girls and decrease slightly among teenage boys. “Although the interaction between gender was statistically significant, the underlying effects for both girls and boys were small,” Nilsen noted. “So I see this as more of a nuance than a surprising finding.”
Translating these statistical changes into real-world terms helps put the findings into perspective. “For girls, a 2-point increase in Gini corresponds to less than a 1 percent increase in the likelihood of depression,” Nilsen said. “To explain the observed increase in depressive symptoms among girls, Gini would have had to increase by about 20 points, which is much more than the municipal changes observed in our data.”
The researchers also investigated whether the effects of inequality take several years to manifest. They tested the data using time lags of up to seven years to see whether economic changes in one year predicted depression rates several years later. During almost all of these delayed periods, results remained virtually negligible.
Although these findings are informative, readers should be careful not to misinterpret them as evidence that income inequality is not a problem at all. “I would also like to preempt one possible misunderstanding: our findings should not be interpreted as saying that inequality is desirable or irrelevant,” Nilsen said. “There may be many good reasons to reduce inequality, such as reducing poverty and improving living conditions.”
The authors note that economic disparities may still influence other psychological or behavioral outcomes, such as risk-taking and extreme competitiveness. “Our study suggests that regional variations in income inequality did not meaningfully predict adolescent depressive symptoms in this particular context,” Nilsen revealed.
This study also faces certain limitations related to its specific geographical setting. Norway is a strong welfare state with universal healthcare, free education, and a strong social safety net. This protective environment may buffer the harshest psychological effects of economic stratification.
“The main caveat is that this study was conducted in Norway, which is a relatively egalitarian country, with limited variation in income inequality within municipalities,” Nilsen said. “The impact may be different in countries where inequality is much greater or where there is greater change over time.”
Future research could benefit from applying this same rigorous approach to different countries. “I think that future research, especially when it comes to income inequality, should continue to use repeated regional data, pre-registered analyses, and clear thresholds for what counts as a meaningful effect,” Nilsen suggested. “It would also be useful to examine whether similar results emerge in countries with high inequality and large changes over time.”
“More broadly, I’m interested in how social and situational context shapes adolescents’ mental health and behavior, and in using designs that better separate differences between regions and changes within regions over time,” Nilsen said. Expanding the scope to include other indicators of psychological well-being may provide a more comprehensive understanding of how the distribution of wealth shapes the developing psyche.
“In my own research, I also plan to investigate other adolescent outcomes, such as bullying and antisocial behavior,” he added. “Income inequality may be more important for these kinds of social and behavioral outcomes than for symptoms of depression.”
“What I want to emphasize is that even null or very small effects can be beneficial if the study is done properly and the design directly addresses the research question,” Nilsen concluded. “In this case, this study does not show that inequality is never important for mental health. However, it does suggest that changes in regional income inequality are likely not the main explanation for changes in depressive symptoms among adolescents from 2010 to 2019 in Norway.”
The study, “Does income inequality predict symptoms of depression in adolescence?” was authored by Sondre Arsene Nilsen, Kire Breivik, Kjell Morten Stoermark and Tormod Bo.
