Researchers used data from a project that tracked U.S. children in seventh grade through adulthood. Those who said they were unhappy as adolescents had incomes in their late twenties that were thirty percent below average whereas those who said they were very happy as kids had incomes ten percent above average.

The connection remained even after the team adjusted the stats to reflect gender age and ethnic backgrounds. While the research didn't prove happy kids have a better chance of making more money, study authors say the findings suggest creating a happy environment for children can help them later in life.

The findings appear in the "Proceedings of the National Academy of Sciences."