Happy childhood equals affluence as an adult?

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. The researchers launched the study to "figure out what happiness actually does," they 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.

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