Protestant churches are losing young adults in "sobering" numbers, a survey finds.

Seven in 10 Protestants ages 18 to 30 — both evangelical and mainline — who went to church regularly in high school said they quit attending by age 23, according to the survey by LifeWay Research. And 34% of those said they had not returned, even sporadically, by age 30. That means about one in four Protestant young people have left the church.

"This is sobering news that the church needs to change the way it does ministry," says Ed Stetzer, director of Nashville-based LifeWay Research, which is affiliated with the publishing arm of the Southern Baptist Convention.

"It seems the teen years are like a free trial on a product. By 18, when it's their choice whether to buy in to church life, many don't feel engaged and welcome," says associate director Scott McConnell.

The statistics are based on a survey of 1,023 Protestants ages 18 to 30 who said they had attended church at least twice a month for at least one year during high school. LifeWay did the survey in April and May. Margin of error is plus or minus 3 percentage points.

Few of those surveyed had kind words for fellow Christians when they reflected on how they saw church life in the four years after high school.

Just over half (51%) of Protestant young people surveyed (both the church dropouts and those who stayed on in church after age 22) saw church members as "caring" or had other positive descriptions, such as "welcoming" (48%) or "authentic" (42%).

Among dropouts, nearly all (97%) cited life changes, such as a move. Most (58%) were unhappy with the people or pastor at church. More than half (52%) had religious, ethical or political reasons for quitting.

Dropouts were more than twice as likely than those who continued attending church to describe church members as judgmental (51% for dropouts, 24% for those who stayed), hypocritical (44% vs. 20%) or insincere (41% vs. 19%)

The news was not all bad: 35% of dropouts said they had resumed attending church regularly by age 30. An additional 30% attended sporadically. Twenty-eight percent said "God was calling me to return to the church."

The survey found that those who stayed with or returned to church grew up with both parents committed to the church, pastors whose sermons were relevant and engaging, and church members who invested in their spiritual development.

"Too many youth groups are holding tanks with pizza. There's no life transformation taking place," Stetzer says. "People are looking for a faith that can change them and to be a part of changing the world."

These findings fit with findings by other experts.

"Unless religious leaders take younger adults more seriously, the future of American religion is in doubt," says Princeton sociologist Robert Wuthnow in After the Baby Boomers, due in stores in September.

The proportion of young adults identifying with mainline churches, he says, is "about half the size it was a generation ago. Evangelical Protestants have barely held their own."

In research for an upcoming book, unChristian, Barna Research Group director David Kinnaman found that Christians in their 20s are "significantly less likely to believe a person's faith in God is meant to be developed by involvement in a local church. This life stage of spiritual disengagement is not going to fade away."

About 52% of American adults identify themselves as Protestant or other non-Catholic Christian denominations, according to the 2001 American Religious Identification Survey. That's down from 60% in 1990.