By John Blake, CNN

(CNN) -True love doesn’t wait after all.

That’s the implication in the upcoming October issue of an evangelical magazine that claims that young, unmarried Christians are having premarital sex almost as much as their non-Christian peers.

The article in Relevant magazine, entitled “(Almost) Everyone’s Doing It,” cited several studies examining the sexual activity of single Christians. One of the biggest surprises was a December 2009 study, conducted by the National Campaign to Prevent Teen and Unplanned Pregnancy, which included information on sexual activity.

While the study’s primary report did not explore religion, some additional analysis focusing on sexual activity and religious identification yielded this result: 80 percent of unmarried evangelical young adults (18 to 29) said that they have had sex - slightly less than 88 percent of unmarried adults, according to the teen pregnancy prevention organization.

The article highlights what challenges abstinence movements face. Movements such as “True Love Waits,” encourage teens to wear purity rings, sign virginity pledges and pledge chastity during public ceremonies.

Yet many of these Christian youths eventually abandon their purity pledges, Relevant’s Tyler Charles concludes in the article. Tyler talked to people like “Maria,” an evangelical woman who said she wanted to wait until marriage to have sex.

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But she said she started having sex with her college boyfriend when she turned 20 because nearly everyone, even most of her Christian friends, were having sex.

Maria:

It seemed everyone in my life, older and younger, had “done it.” In fact, I waited longer than most people I knew and longer than both of my sisters, even though we were all Christians and came from a good home.

Relevant theorizes about why it’s so hard for so many young Christians to wait, including the saturation of sex in popular culture, the prevalence of pornography and a popular “do what feels good philosophy.”

Yet the article also asks a question that rarely comes up in discussions about abstinence movement. Relevant notes that in biblical times, people married earlier. The average age for marriage has been increasing in the U.S for the last 40 years.

Today, it’s not unusual to meet a Christian who is single at 30 - or 40 or 50, for that matter. So what do you tell them? Keep waiting?

Scot McKnight, author of “The Jesus Creed,” and "One.Faith: Jesus Calls, We Follow," acknowledges that young, single Christians face temptations that their counterparts in the biblical age didn’t face.

He tells Relevant:

Sociologically speaking, the one big difference – and it’s monstrous – between the biblical teaching and our culture is the arranged marriages of very young people. If you get married when you’re 13, you don’t have 15 years of temptation.

So what should a Christian parent or youth pastor do? How do they convince more young Christians to wait until marriage, or should they stop even trying?