The study, published in Psychological Science, a journal of the Association for Psychological Science, said roughly 85 percent of movies released from 1950 to 2006 contained sexual content, and only 9 percent of sexual content in movies contained messages promoting sexual health. Sexual explicitness of PG-13-rated and R-rated movies has increased over the past decade, researchers also said. Evidence suggests that adolescents' sexual attitudes and behavior are influenced more by movies than by other forms of media, the study said.
Allen Jackson, director of the Youth Ministry Institute at New Orleans Baptist Theological Seminary, likened it to a pregnant woman drinking alcohol.
"There's an enhanced risk at that life stage," Jackson said. "There is an enhanced impact of the images that are viewed."
The effect of media on sexual behavior, the study said, is driven by the acquisition and activation of "sexual scripts." In behavioral psychology, a script is a sequence of expected behavior for a given situation. A higher degree of sexual media exposure, researchers said, has been found to predict more permissive sexual attitudes.
Adolescents sometimes seek out sexual media, possibly to learn scripts, the study said, noting that 57 percent of U.S. adolescents ages 14 to 16 reported using media as a primary source of sexual information.
This particular study examined why movies impact adolescent behavior, looking closely at the role of a personality trait known as sensation seeking, a tendency to seek novel and intense stimulation. Adolescents, experts said, have a predisposition for sensation seeking behavior, which peaks between the ages of 10 and 15.
"It is important to note that sensation seeking arises from both biological and socialization factors ..., which suggests that environmental influences, such as [movie sexual exposure], could affect the development of this trait," the study said.
"One promising approach would involve incorporating media-literacy training into sexual education," the authors said. "A recent intervention showed that a peer-led sexual-media-literacy curriculum increased ninth-grade students' self-efficacy in resisting peer pressure with regard to sexual behavior, reduced their perception of the normative prevalence of sexual activity during adolescence, and improved their attitudes toward abstinence."
Identifying risk factors for early sexual debut and sexual risk taking is an important public health concern, the study said, and delaying adolescents' sexual debut could curb U.S. rates of sexually transmitted infections and instances of unplanned pregnancy.
The study, initially published online July 18, recruited more than 1,200 participants who were from 12 to 14 years old and asked them to report which movies they had seen from several different collections of 50 that were randomly selected.
Participants reported how often they attended church or engaged in religious activities, how many hours of television they watched each day, whether they had a television in their bedroom, and with whom they lived (to determine family structure as intact or divided).
Six years later, the participants were surveyed to find out how old they were when they became sexually active and how risky their sexual behavior was.
"This study, and its confluence with other work, strongly suggests that parents need to restrict their children from seeing sexual content in movies at young ages," O'Hara said.
Ross, the student ministry professor, told Baptist Press when film studios spend millions to make sexual content powerful and when adults give youth permission to view such content, real consequences in real lives will result.
"What teenagers most need is a new set of 'movies.' The Bible is the 'novel.' Teenagers need to read and study the book, absolutely. But they also need to see the 'movie' based on the book," Ross said. "They need Mom and Dad and their leaders to live out -- in high definition -- what life looks like based on the book.
"If we only prohibit bad movies, we leave a vacuum. We need to replace them with 'movies' that star parents and leaders who reveal what it means to love God, to love others and to join Christ in bringing His Kingdom on earth," Ross said.
Jackson, of the Youth Ministry Institute, said conservatives and liberals alike can find common ground regarding media literacy. An example, he said, is the fact that cigarette ads no longer appear on television or in print.
"Media literacy groups said you shouldn't use advertising tricks on children. You shouldn't have a cartoon camel selling cigarettes to make children think it's OK," Jackson told BP.
"There are voices from both the very liberal and the very conservative that say we should monitor what children see in the way of media because all of the camera angles and multiple scene changes and special effects are almost like an unfair advantage influencing the lives of children," he added.
Jackson recommended the Center for Parent/Youth Understanding as a resource for parents who want to be proactive in the battle to raise godly children in the current media climate.
"Walt Mueller is one of the most respected faith-based voices in this whole area, and there are hundreds of free resources including the Digital Kids Initiative, which is on the cpyu.org website," Jackson said, noting that the initiative is a media literacy guide for Christian parents.
Parents, Jackson said, should watch a television show with their children and ask questions such as, "What is the message behind the message? Was there an agenda in that show? If we heard profanity, why is it in there? Why would we listen to that? What's the lifestyle that's glorified? What's the worldview that's inherent in the show?"
When special effects are used onscreen, parents should help children sort fact from fiction, Jackson said.
"I'm not one that says we should seclude our children from media, although I respect the parents that do so," he said. "It's quite a useful thing for parents to watch a movie or to watch a commercial or to watch a television show with their children and employ active media literacy principles even as they do so."