TUESDAY, Nov. 10, 2015 (HealthDay News) -- Americans 30 and older are less happy than generations past, while teens and 20-somethings seem more satisfied with their lives than ever, a new study finds.

Researchers said the pattern marks a striking reversal of what studies have traditionally shown -- that, on average, people become happier as they mature.

It looks like that age advantage has disappeared. The average happiness rating among Americans aged 30 and older now matches that of younger Americans.

"A lot of the change has happened in just the past five years," said lead researcher Jean Twenge, a professor of psychology at San Diego State University.

The reasons are not clear, said Twenge. But she speculated on some possible explanations.

Other research has shown that in recent decades, young Americans' expectations about their future -- their jobs, income, relationships -- keep growing. But reality isn't keeping up, Twenge pointed out.

"Around the age of 30 or so, you start to figure that out," she said.

It's also likely that recent cultural shifts are playing a major role, added Twenge.

She said social media -- and the technology that keeps it at our fingertips 24 hours a day -- may feed young people's need for stimulation, attention or a sense of belonging to a large group of "friends."

"Once you're a little older, though, that doesn't cut it," Twenge said. "You may want to settle down, have more-stable relationships, and have a sense that you're part of a community."

James Maddux, a researcher who wasn't involved in the study, agreed.

"Technology may be feeding a need for younger folks, but it's just not enough for 'older' people," said Maddux, a senior scholar at the Center for the Advancement of Well-Being at George Mason University in Fairfax, Va.

Compared with past generations, Maddux said, many more Americans live alone -- owing to delays in marriage and a high divorce rate. And some traditional ways of connecting to community, such as going to church, are also on the wane.

Although other types of community groups abound, Maddux added, many Americans might not take advantage of them.