Keio University Research: Study Reveals How Happiness and Health are Linked across Generations

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Keio University

Oct 30, 2026, 20:29 ET

Analysis of Japanese families finds that happiness shows a stronger parent–child connection than general or mental health, but well-being is less closely tied across generations than income.

TOKYO, Oct. 31, 2026 /PRNewswire/ -- A person's happiness and health are associated with those of their parents, but these connections are far from inevitable. Researchers at Keio University have found that happiness, general health, and mental health all show measurable similarities between parents and their adult children in Japan. Of the three, happiness showed the strongest relationship.

Published in Review of Economics of the Household, the study draws on long-term survey data covering two generations of Japanese families. The findings suggest that inequality extends beyond income and education to include people's experiences of happiness and health. They also show that well-being is less strongly linked between generations than household income.

Looking beyond income and education

When researchers study inequality, they usually examine differences in income, wealth, education, and occupation. These measures help reveal whether children born into disadvantaged families are likely to face similar disadvantages as adults.

But economic circumstances are only part of what determines how well people live. Two people with similar incomes may have very different experiences of happiness, physical health, or psychological well-being. This raises an important question: are people whose parents enjoyed happier and healthier lives more likely to experience the same advantages themselves?

Kayoko Ishii, Zhi-xiao Jia, and Isamu Yamamoto of Keio University investigated this question by examining intergenerational persistence—the extent to which a characteristic remains associated between parents and their children.

"Our main question was how strongly subjective well-being is related between parents and children," explains Ishii. "Previous work on intergenerational inequality has mainly focused on objective outcomes, such as income, education, and occupation."

The researchers examined three aspects of subjective well-being: happiness, people's assessments of their general health, and their mental health.

Following Japanese families across generations

The study was made possible by the Japan Household Panel Survey, a long-running research program associated with Keio University's Panel Data Research Center.

Beginning in 2004, the survey repeatedly collected information from the same individuals over many years. It was subsequently extended to include the adult children of participants, including those who no longer lived with their parents. This allowed the researchers to compare two generations within the same families.

"We have followed the same individuals for more than 20 years, asking many of the same questions each year," says Ishii. "The survey has also been expanded to their adult children, allowing us to link information on parents and children."

Following people over time is especially important when studying happiness and health. Well-being can change with age, employment, family circumstances, or illness. A single survey response may therefore reflect a temporary situation rather than someone's longer-term experience.

By combining observations from different years, the researchers constructed estimates intended to better represent well-being over the course of people's lives. They then compared the relative positions of parents and children within their respective generations.

Happiness shows the strongest connection

The analysis found statistically significant parent–child associations for all three measures of well-being. The researchers estimated a relationship of 0.25 for happiness, 0.22 for self-reported general health, and 0.13 for mental health, using a statistical measure known as the rank–rank slope.

A larger value indicates a stronger association between the relative positions of parents and children. Happiness was therefore the most persistent of the three measures, while mental health showed the weakest connection. These figures do not mean that parents determine a particular percentage of their children's happiness.

Importantly, subjective well-being was generally less persistent across generations than household income in Japan. This suggests that people's experiences of happiness and health may be more independent of their parents' circumstances than their economic position.

The researchers also investigated possible explanations. Income, education, lifestyle, and personality accounted for only part of the association. Among personality traits, agreeableness—the tendency to be cooperative and considerate of others—made a modest contribution to the relationship in happiness. Much of the association remained unexplained.

The relationship also appeared somewhat stronger in wealthier households, although the difference was not statistically significant.

Why these findings matter

The study broadens the discussion of inequality by showing that advantages and disadvantages can extend beyond material circumstances.

"Traditionally, attention has been focused on disparities in income and assets," says Yamamoto. "But we must also examine inequality in other non-monetary aspects of life, such as health and well-being."

"Some disparities inevitably emerge as people compete with each other," Yamamoto explains. "But it is more concerning when differences in individuals' starting points strongly affect their access to opportunity later in life."

Compared with findings from other countries, Japan showed an intermediate degree of intergenerational persistence in subjective well-being. Differences in healthcare, welfare systems, and other institutions may contribute to variation between countries, although this study does not establish their causal effects.

The findings suggest that efforts to reduce inequality may need to consider more than financial assistance and educational opportunity. Access to healthcare, psychological support, and family welfare could also be relevant to creating more equal opportunities for well-being.

Study limitations

The study identifies associations rather than proving that parents directly transmit happiness or health to their children. Genetic influences, shared environments, economic circumstances, and other factors may contribute.

The available data covered only two years for the children's generation and for mental health in both generations, making estimates of longer-term well-being less certain than those based on more extensive observations. Further research using longer-term data and comparisons across countries is needed.

Nevertheless, the findings add an important dimension to the study of social mobility: whether people can improve not only their economic circumstances, but also their chances of living happy and healthy lives.

Glossary

Subjective well-being: People's own assessments of their happiness, health, or quality of life.

Intergenerational persistence: The extent to which characteristics such as income, happiness, or health are associated between parents and their children.

Panel survey: A study that repeatedly collects information from the same people over time.

Rank–rank slope: A statistical measure of how strongly a parent's relative position within one generation is associated with a child's relative position within the next.

About the researchers

Kayoko Ishii ― Project Associate Professor 
Faculty of Economics

She holds a Ph.D. in Business and Commerce from the Graduate School of Business and Commerce at Keio University. She is currently a project associate professor in the Faculty of Economics at Keio University. Her research focuses on employment, income inequality, and subjective well-being, using household panel data to examine changes over time and across generations. 

Isamu Yamamoto ― Professor 
Faculty of Business and Commerce

He holds a Ph.D. in Economics from Brown University. He is currently a professor in the Faculty of Business and Commerce and the director of the Panel Data Research Center at Keio University. His research focuses on labor economics and applied economics.

Links

Reference

Ishii, K., Jia, Z.-X. & Yamamoto, I. Intergenerational persistence of subjective well-being: Evidence from the Japanese Household Panel Survey on parents and children. Rev Econ Househ 23, 1047–1074 (2025).

Funding

The study acknowledges support from the Japan Society for the Promotion of Science (JSPS) [grant numbers 22H04911].

Keio Research Highlights   
https://research-highlights.keio.ac.jp/

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SOURCE Keio University