“Millennial adolescents are less religious than Boomers and GenX’ers were at the same age," Twenge continued. "We also looked at younger ages than the previous studies. More of today’s adolescents are abandoning religion before they reach adulthood, with an increasing number not raised with religion at all.”

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Compared to the 1990s, 20 percent fewer college students described themselves as above average in spirituality, suggesting that religion has not been replaced with spirituality.

"These trends are part of a larger cultural context, a context that is often missing in polls about religion,” Twenge said. “One context is rising individualism in U.S. culture. Individualism puts the self first, which doesn't always fit well with the commitment to the institution and other people that religion often requires. As Americans become more individualistic, it makes sense that fewer would commit to religion.”