"We were encouraged that sex education is working," says Trisha Mueller, MPH, an epidemiologist at the CDC in Atlanta who led the study. "Sex education should continue to be implemented."
Ninety-three percent of Americans support sex education in some form, and the teaching of it has become widespread in schools and other institutions, according to Mueller. Previous studies have produced conflicting results on whether sex ed works, Mueller says, yet few recent studies have looked at its impact using a large sample that is nationally representative.
That was the impetus for her study, in which she and her co-authors looked at a nationally representative sample of 2,019 teens, aged 15 to 19, who responded to the 2002 National Survey of Family Growth.
The teens were asked whether they had received any formal sex education instruction at school, at church, or through community organizations. They reported on whether they were instructed about how to say no to sex and whether they got information on birth control.
The study didn't try to prove which of the two approaches -- practicing abstinence or learning contraceptive skills as well as the value of delaying sexual activity -- is better, Mueller tells WebMD.
Teens also reported their age when they received the sex education and their age at first intercourse. Researchers categorized age at first sex as over 15 or under, to coordinate with the government's Healthy People 2010 goal of increasing the proportion of teens who abstain from sex until at least age 15.
Finally, the researchers compared those who had sex education before their first intercourse with those who had it after and those who had no sex education. They did not look at oral sex practices, Mueller says.
Their major findings, published in the January issue of the Journal of Adolescent Health:
- Teenage girls who received sex education had a 59% reduced risk of having sexual intercourse before age 15 compared with those who did not get sex education before their first intercourse.
- For teenage boys, sex ed before first intercourse had a 71% reduced risk of having intercourse before age 15 compared with those boys who did not get sex ed before their first intercourse.
- For high-risk groups, the benefit was even greater. African-American urban teenage girls who got sex ed before their first intercourse had an 88% reduced risk of having sex before age 15, Mueller says, compared with those who did not get the training.
Teenage boys who were in school or had graduated and had sex ed were about three times more likely to use birth control when they first had sex compared with those who were in school or had graduated and didn't get sex ed.
Perspective on Sex Ed
Earlier studies have not always found a beneficial effect for sexual education, Mueller tells WebMD. As to why her study did, she says "it could be related to the fact that we were able to control for the sequence of events." That is, they knew if the sex education had taken place after sexual activity had begun or not.
"Receiving sex education before the first sexual activity has the most positive outcome," she says.
The age at which sex ed is taught varies, but a recent national study of middle school teachers found that 72% of fifth- and sixth- grade teachers reported that sex education was taught at their school at one or both grade levels.
"This study is one more piece of evidence that sex education has the potential to influence teen sexual behavior in a positive way," says Laura Lindberg, PhD, a senior research associate at the Guttmacher Institute, a New York based nonprofit organization focused on sexual and reproductive health research and policy analysis.
Still, the study has limitations, she tells WebMD. "The study doesn't shed light on the debate about which approach is better." Other research does, however, she says.
"It's a big-picture study," she says of the CDC research. And the increased benefit to high-risk groups, she says, is not that great.
Message for Parents
Sex education should not be confined to one class, Lindberg says, but parents shouldn't leave it all to the schools, either.
"It's important to have ongoing, age appropriate sex education," she says. "You're providing your children sex education when you teach them the name of body parts, when you kiss your husband in front of them."