Happiness over one’s lifetime has been popularly described as looking like a U-shaped curve: The joys of youth are followed by the challenges of our 20s and 30s before an upswing later in life that reaches a peak after retirement.

While that may be true – or not – in wealthier countries such as the United States, it doesn’t apply to low-income, nonindustrialized societies. That is the main finding of a study I led that examined aging in rural, subsistence-oriented communities in 23 countries across the Global South. And our results have implications for global health amid aging populations and growing economic insecurity.

In our study, we found that happiness levels did not consistently follow the U-shaped trajectory commonly observed in industrialized societies. In some cases there was a U-shape. But more often we observed an inverted U-shape, where middle-aged adults reported the highest level of happiness, or no significant age-related trend at all.

Overall, well-being often declined after middle age among resource-poor populations lacking social security and other institutionalized forms of protection. This aligns with prior research among low-income countries and even of wealthy nations during economic crises.

That being said, age itself was a weak predictor of life satisfaction everywhere. Sickness, disability and loss in productivity do a better job of explaining well-being than age. In fact, the few positive effects of age we did find usually disappeared when including measures of these misfortunes in our analysis.

Along with other developments showing lower well-being among adolescents and young adults in recent years, my research challenges the assumption that the U-shaped happiness curve is universal. The trend showing that average well-being improves after middle age might be more typical of urban, affluent societies with formal retirement and strong safety nets for older adults. By examining a broader range of settings, we gain insight into how environmental and socioeconomic factors shape well-being over a lifespan, offering a more nuanced perspective on happiness that could guide policies for different age groups and cultures.

I believe understanding well-being across diverse cultures is crucial, especially amid global aging and mental health crises. By reconsidering the determinants of happiness outside the U-shaped model, we’re all better positioned to improve quality of life for different populations worldwide.

Michael Gurven receives funding from National Institutes of Health / National Institute on Aging (NIH/NIA).