"No single reason dominated the break-up between church and young adults. Instead, a variety of reasons emerged. Overall, the research uncovered six significant themes why nearly three out of every five young Christians (59%) disconnect either permanently or for an extended period of time from church life after age 15.
Reason #1 – Churches seem overprotective.
Reason #2 – Teens’ and twentysomethings’ experience of Christianity is shallow.
Reason #3 – Churches come across as antagonistic to science.
Reason #4 – Young Christians’ church experiences related to sexuality are often simplistic, judgmental.
Reason #5 – They wrestle with the exclusive nature of Christianity.
Reason #6 – The church feels unfriendly to those who doubt."
Barna.org, September 28, 2011
See the original article for further description of the reasons why young people leave the church.