A new study, published Thursday in the journal Social Psychological and Personality Science, found that the old adage that people over 30 are happier than teenagers and young adults may no longer be true.

Looking at data from the 1970s through the present, the authors of the study found that until recently, adults over age 30 reported being happier than did young adults and teens. But “adolescents in recent years were happier than adolescents in previous decades,” the authors write. As a result, the gap has closed between the two groups’ self-reported happiness levels. All the data analyzed by the researchers was self-reported by the study participants.

The study authors propose some reasons this could be the case: “Cultural shifts toward individualism may favor adolescence, a time of self-focus… The weakening of social ties (such as the lower marriage rate), economic circumstances such as the Great Recession, and growing income inequality may also have a larger impact on adults than on adolescents.”

Still, one in three American adults reported being “very happy.”

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Write to Tessa Berenson at tessa.berenson@time.com.