Can money buy happiness? Yes, claim the authors of a new study -- but only up to a point.

Psychology has shown that richer people generally rank the overall quality of their lives more favorably than poorer people do. At the same time, their actual happiness seems to be motivated less by their ability to buy more than by being able to keep up with those with comparable resources in their own age group (five years older or younger), according to a new study.

"Our findings point to the possibility that, rather than promoting overall happiness, continued income growth could promote an ongoing consumption race where individuals have to consume more and more, just to maintain a constant level of happiness," writes Glenn Firebaugh of Pennsylvania State University.

The study was presented at the American Sociological Association's 100th Annual Meeting.

Whether the affluent are happier as a whole than their less well-to-do counterparts is becoming an increasingly hot topic for debate. In recent years, much has been written regarding the "science of happiness."

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Richer people are happier because money can purchase goods and services and it is the consumption of these materials that increases one's enjoyment of life and one's sense of well-being, they write.

As incomes in the U.S. tend to rise over the course of our lifetimes, individuals may find themselves on a sort of treadmill, consuming more and more just to maintain a constant level of happiness, they write.

Researchers used what they call the hedonic treadmill hypothesis, where nothing is ever quite enough, to analyze the association between income and happiness.

Firebaugh and his colleagues measured the age, total family income, and general happiness of individuals aged 20 to 64, generally considered the working life span for most Americans.

The results suggest that Americans are on a hedonic treadmill for most of their working lives.

Regardless of such criteria as physical health, education, effects of getting older, race, and marital status, people's happiness was affected by what others earned. The higher the income of others in one's age group, the lower one's happiness.

The finding suggests that working families must earn more and more over time to maintain a certain constant level of happiness. On the other hand, they add that "families whose income earners are on a flat trajectory are less likely to be happy over time."

"We must be careful not to exaggerate the consequence of this phenomenon, since income is only one determinant of happiness."

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By Patti Connor, reviewed by Brunilda Nazario, MD

SOURCES: American Sociological Association 100th Annual Meeting, Philadelphia, Aug. 13-16, 2005. News release, American Sociological Association. The Economist, Aug. 10, 2003.