Half of all U.S. high school students say they have had sex, and about 900,000 teenage girls become pregnant each year. Adolescent girls can be particularly vulnerable to violence, and studies have shown higher rates of violence perpetrated by a date for teenage girls than for adults. One in 10 intentional injuries to teenage girls is from an intimate partner (nearly always a male), and researchers at the Harvard School of Public Health looked at what factors put girls at risk for violence and how it affected them.

What the researchers wanted to know: How prevalent is violence between teenage girls and the boys they hook up with, and what are the health consequences of dating violence?

What they did: The researchers used data from the 2001 national Youth Risk Behavior Survey, a survey given to thousands of students in grades 9 through 12 every two years and run by the Centers for Disease Control and Prevention. Researchers used the answer to the question "During the past 12 months, did your boyfriend or girlfriend ever hit, slap, or physically hurt you on purpose?" to assess whether girls had been victims of dating violence. They compared the answer to this question with answers to questions about sexual behavior.

What they found: Girls who had had sex were much more likely to be victims of dating violence than those who had not. Eighteen percent of girls who were sexually active had been victims of violence, versus 4 percent of girls who had never had sex. The victims of dating violence were also much more likely to engage in risky sexual practices such as multiple partners, having sex before the age of 15, not using a condom, and using alcohol or drugs before sex. Girls who had been intentionally hurt by their boyfriends were twice as likely to be pregnant as other girls—perhaps because they felt intimidated and therefore less likely to insist on the use of birth control.

What it means to you: The researchers broke down victimization by ethnicity and geographic region and found only one significant predictor of dating violence: Teenagers living in the country and inner city are more susceptible than those living in suburban areas. Because suburban schools often have more money and better access to information than inner-city or rural schools, this statistic suggests that education can help. The researchers encourage more education for teens on how to handle violence and further studies on males to figure out what gives rise to their violent behavior.

Caveats: The study used only one question to assess whether teenage girls had been victims of their boyfriend's violent behavior. Girls may not have responded yes if they did not believe that their boyfriend's behavior was intentional, if it happened only once or twice, or if they didn't think it was severe enough to count as being physically harmful. In addition, nearly 70 percent of the teenagers who responded were white, and all were in school, so the data may not apply to girls who aren't white or who drop out of school.

Find out more: CoolNurse.com was started by a nurse to address the health concerns of teenagers. The site has information on everything from homemade facial masks to sexual fetishes, as well as a good page on dating violence.

The Alabama Coalition Against Domestic Violence has a more academic site, including a "Dating Bill of Rights" to help people who feel they may have been victimized.

Read the article: Silverman, J.G., Raj, A., and K. Clements. "Dating Violence and Associated Sexual Risk and Pregnancy Among Adolescent Girls in the United States." Pediatrics. August 2004, Vol. 114, No. 2, pp. e220–e225.

Abstract online: http://pediatrics.aappublications.org