In a survey conducted by The Huffington Post U.K. Lifestyle Web site, respondents said they felt better about themselves and their lives in their 30s than when younger.
"In a time when the anti-aging industry reigns supreme, it is refreshing to see evidence that maturity, far from being a negative state, is rather the key to true contentment and inner well-being," the Web site's editor Georgia James told The Daily Telegraph.
Twentysomethings were more likely to care more about money than their health, the poll found, and to look enviously at their friends' lifestyles.
They even spent more time worrying about getting old.
While the majority of poll respondents tagged 38 as the "happiest" age, older respondents said happiness reached its peak at 48, "reinforcing a belief that age and experience provide a wealth of benefits," James said.
The poll was conducted among 2,000 adults 18 and over, but actual percentages or margins of error were not released.