MONDAY, Nov. 19 (HealthDay News) -- Do you know a happy kid? Good news: He or she is more likely than an unhappy child to be more affluent later in life.

So finds a new study that links well-being in American adolescents to greater wealth by the time they reach 30.

The research doesn't definitively prove that happy kids have a better chance of making more money when they grow up. And it's not clear if inheriting money -- or marrying into it -- could be important factors.

Still, the findings do suggest the value of creating happy environments for children, said study co-author Andrew Oswald, a professor of economics at the University of Warwick in the United Kingdom. "If you take our work at face value, it suggests that if you could make young Americans happier, then they would later become richer. It is possible that could work for a whole economy. A happier U.S. would translate, eventually, into a richer one."

The researchers launched the study to "figure out what happiness actually does," Oswald said. "We might think that human happiness is important in itself as a goal, but does it cause other things, perhaps other good things?"

To find out, the researchers examined a research project that tracked U.S. kids from grades 7 to 12 into adulthood. Researchers last interviewed the remaining participants -- almost 16,000 people -- in 2008.

Overall, those who said they were very unhappy as adolescents had incomes around age 29 that were 30 percent below the average, the study found. On the other hand, those who said they were very happy as kids had incomes that were 10 percent above the average.

The researchers found a connection between happiness and later wealth even after adjusting the statistics so they wouldn't be thrown off by larger or smaller numbers of participants who were of certain ages, genders, IQs and ethnicities, among other factors.

The study also examined how happiness after childhood might affect wealth. Oswald's team found that a one-point increase in life satisfaction (on a scale of 1 to 5) at age 22 was associated with a growth in annual income of about $2,000 by the age of 29, although it's not clear if the two events are directly linked.

Why might happier kids become richer adults? "Certainly, faster job promotion is part of it," Oswald said. "Maybe that is because happier people fit in better in organizations and make a useful contribution to others' happiness and productivity."

That theory makes sense to Sonja Lyubomirsky, a professor of psychology at the University of California, Riverside, who studies happiness. Happy people are more likable, make a better impression at job interviews and are more likely to get jobs, she said.

Lyubomirsky noted that society focuses on making money to become happy, but the study suggests that the relationship might work both ways.

"This says that if you're happy, you can be more successful. If you put work into becoming a happier person, you can get a lot of benefits from it -- one of them being more money," she said.

The study was published online Nov. 19 in the Proceedings of the National Academy of Sciences.

More information

Want to boost your happiness by lowering anxiety? There are tips on doing so at the U.S. National Library of Medicine.