Though a majority of teens and young adults identify as Christian, a new study suggests that only 15 percent of them have personal relationships with Christ and are deeply committed.

Most American "Millenials" – those born between 1980 and 1991 – don't pray regularly. Few read their Bibles or other religious texts, and many don't attend church on a weekly basis, according to a LifeWay Research study.

"[W]e cannot forget the vast majority of lost young people in this generation. Our hearts should be broken with this reality," said Thom Rainer, president of LifeWay Christian Resources. "We should be convicted if we do not yet have a heavy burden to reach this generation."

Sixty-five percent of Millennials called themselves a Christian in the study that was conducted on 1,200 young Americans in August 2009. But Rainer estimates that 85 percent of young people are lost.

"Many are either mushy Christians or Christians in name only," Rainer told USA Today. "Most are just indifferent. The more precisely you try to measure their Christianity, the fewer you find committed to the faith."

According to the study, one-third of all Millennials agreed strongly that they have made a personal commitment to Jesus Christ that is still important in their life today. Nearly a quarter agreed somewhat.

Rainer, who has been researching the younger generation for an upcoming book, has hope in the few who are deeply committed Christians.

"Millennial Christians will not settle for business as usual in our churches," he said. "They will not be content with going through the motions, programs without a purpose, and spectator Christianity. They take their faith seriously, and they have little patience with churches that focus most of their resources on the members."

While most surveyed young people believe Christian churches are relevant today, only 28 percent agreed strongly.

Half of those who trust Christ as Savior, and 67 percent who self-identified as "Christian" indicated they do not attend worship services on a weekly basis.

More than half (56 percent) of self-identified Christians rarely or never read the Bible and 38 percent rarely or never pray by themselves.

Notably, almost three out of four Millennials agreed that they are more spiritual than religious. Even those who trust Christ as Savior were particularly likely to describe themselves as more spiritual than religious (74 percent).

The study noted that the popular SBNR label "is no longer a term that means 'I don't have any particular beliefs but believe in spirituality in general.'"

Forty-four percent of self-identified Christians agreed strongly that Jesus is the only way to Heaven. Among those who trust Christ as Savior, 81 percent agreed strongly. Only 16 percent of young people who don't attend religious worship services indicated the same strength of accord.

Moreover, 26 percent of Christians agreed strongly that salvation is through God's grace alone.

In other findings, only a quarter agreed strongly that the Bible is the written word of God and is totally accurate in all that it teaches. Only 30 percent strongly believe Jesus Christ was sinless. And the most common belief among Millenials about life after death is that "no one really knows."

"Millennials are the most religiously diverse generation in our culture’s history," Rainer said. "Unsure of the afterlife and the life of Jesus, Millennials present the church with a great opportunity to engage them in conversations dealing with the nature of truth and its authority as God."