In this issue.

A nation can invest in its youth in many ways, including through investments in education, in community programs and in health services. Some approaches are more enduring than others, most notably among them, ones that provide the information that helps set agendas and determine priorities. When Congress authorized and appropriated funding for a nationwide, longitudinal study of the determinants of adolescent health, whether knowingly or not, it chose an investment strategy of long-term value.

The principal investigator and study team at the University of North Carolina-Chapel Hill who designed and implemented the National Longitudinal Study of Adolescent Health (Add Health) were also charged with responsibility for turning that repository of information into a public-use data set as soon as possible. As hundreds, if not thousands, of researchers know, the Add Health study is a gold mine of opportunity for understanding the determinants and trajectories of adolescent health and risky behavior. Likewise, its inclusion of protective factors in the lives of adolescents permits analysis of the experiences, events and opportunities that can buffer young people from harm and increase the likelihood of positive outcomes. This complex data set, which links individual respondents to their respective family, school and community contexts, now includes three waves of data that allow investigation of adolescents' transition into young adulthood. Add Health's depth, breadth and longitudinal design give it enduring value to researchers, as well as to those who promote evidence-based programs, policy and practice.

This issue of Perspectives on Sexual and Reproductive Health comprises Add Health analyses focused exclusively on sexual behavior and reproductive health, and represents a valuable resource to inform further research and its application to prevention and health promotion efforts.

* The article by Ramesh Raghavan and colleagues (page 225) demonstrates a continued interest in the predictive power of prior circumstances on repetition of those circumstances. Here, the core question is whether prior sexual victimization increases the risk of subsequent sexual victimization among teenage females. The results provide the first national prevalence estimates of forced sexual intercourse and revictimization among females in grades 7-12, also demonstrating that for many, first intercourse may have been forced. The authors show that the experience of victimization does not necessarily auger a repeat of the same experience. Instead, they describe a synergy between individual and interpersonal factors (such as substance use and sexual dating partners) that may increase exposure to unsafe situations, thereby increasing the likelihood of sexual victimization and revictimization.

* The Centers for Disease Control and Prevention's (CDC's) 1993 recommendation that all sexually experienced teenage females be screened annually for Chlamydia trachomatis is the frame of reference for the article by Lynne Fiscus and colleagues (page 233). They use the initial wave of Add Health data, from 1995, to provide the first published national estimate of the prevalence of annual sexually transmitted disease (STD) screening in this population. Their results demonstrate a substantial gap between this standard of care and the receipt of services by adolescent females two years after the CDC made its recommendation.

* Carolyn Halpern and associates (page 239) focus on risk of STD acquisition, with particular attention to the co-occurrence of drug and sexual risk behaviors, and to differences in patterns of covariation between black and white youth. They seek to illuminate critical underlying questions that inform prevention and health promotion strategies: Do common etiologies of health-jeopardizing behaviors cut across various social groups of adolescents? Or are behavioral risk patterns particular to specific groups, suggesting the need for tailored prevention efforts? The analysis points to the need for data that go beyond the scope of Add Health on the nature and prevalence of "cross-over" behaviors that put females who are at low risk, especially black females, in contact with male partners with a higher risk.

* Hannah Bruckner and coauthors (page 248) focus on young people's attitudes toward contraception and pregnancy as risk factors for pregnancy. Notably, in this sample, strongly held attitudes against pregnancy were unrelated to contraceptive use or subsequent pregnancy, and increasingly positive attitudes toward contraceptive use were predictive of a greater likelihood of actual use. Sexually experienced females who held no opinion about pregnancy (described by the authors as ambivalent) were at greater risk of poor contraceptive use than were those with any opinion, either favorable or unfavorable. At the same time, the presence of an opinion about pregnancy did not differentiate consistent from inconsistent contraceptive users. By clarifying these relationships, this analysis suggests the utility of paying close attention to attitudes toward contraceptive use, since consistent, effective use reliably reduces the risk of pregnancy.

* In their examination of Wave 3 data (page 258), Carol Ford and colleagues assess another set of perceptions-the extent to which sexually experienced young adults (aged 18-26) perceive themselves to be at risk for Chlamydia trachomatis or Neisseria gonorrhoeae. An internalized, personalized sense of risk of STD acquisition is an essential component of both preventive and help-seeking behavior. It is disturbing (but not surprising) that the majority of young adults who are at risk for or actually have chlamydial or gonococcal infection do not perceive themselves as high-risk. These findings have urgent implications for public health education, for implementation of existing standards of care that call for annual testing of sexually experienced females, and for adoption of a similar standard for sexually experienced males.

* Patterns of contraceptive use in teenagers' most recent sexual relationships are the primary focus of Jennifer Manlove and associates' examination of multiple influences, including partner and relationship characteristics, contraceptive use in first sexual relationships, sexual history, and family and individual factors (page 265). Utilizing Wave 1 and 2 data, their results affirm the inconsistency of adolescent contraceptive use both within and across relationships and the variegated effects of factors influencing this critical outcome. Parallel analyses by gender underscore an important understanding: The only significant characteristic predictive of contraceptive use and consistency of use at most recent intercourse for both males and females was the use of contraception with the first sexual partner.

* Dawn Upchurch and colleagues (page 276) capitalize on Add Health's inclusion of multilevel contextual factors to examine individual, fatally, school and neighborhood characteristics associated with the report of an STD at Wave 1 and the association of those factors with self-reported STD acquisition between Waves 1 and 2. Uniquely among this set of studies, this one includes among the predictor variables measures of residential stability and the proportion of adults who are unemployed. The authors are particularly interested in whether age at first intercourse and STD history at Wave 1 persist as significant determinants of STD acquisition in light of other determinants. Their findings affirm the importance of including measures of adolescents' multiple social contexts in future studies of adolescent sexual behavior and outcomes.

It has now been seven years since the publication of the first paper from the National Longitudinal Study of Adolescent Health. The availability of Wave 3 data creates exciting, unparalleled opportunities to study continuities and discontinuities of behavior. As a community of researchers, we are poised to gain greater understanding of trajectories of risk and protection for adolescents and young adults, and to collaborate with colleagues working with and on behalf of young people to move these insights into direct application.

Michael Resnick

Member of the Add Health Research Team

Guest Editor