Boyfriends, girlfriends and teenagers' risk of sexual involvement.

CONTEXT: Having a boyfriend or girlfriend, especially an older one, is associated with increased sexual risk in early adolescence. The mechanisms underlying this association are unclear.
METHODS: Middle school students in Northern California were surveyed annually from 1997 to 2000. For a sample of 1,214 males and 1,308 females who were sexually inexperienced in seventh grade, logistic and linear regression were used to explore associations between relationship status in seventh grade and sexual activity in ninth grade, controlling for sixth-grade and eighth-grade characteristics.
RESULTS: Males who had had a girlfriend their age by seventh grade were more likely than those who had had no relationship to report sexual activity in ninth grade (odds ratio, 2.1). Similarly, for females, the odds of being sexually active in ninth grade were elevated among those who had had a boyfriend their age (2.9); however, they also were higher among those who had had an older boyfriend than among those who had had one their age (2.1). With sixth-grade risk factors controlled, relationship status in seventh grade remained significant only for females; the association was explained by early menarche and by participation in situations that could lead to sex and riskier peer norms in eighth grade. For males, eighth-grade situations that could lead to sex, Hispanic ethnicity and sixth-grade peer norms explained ninth-grade sexual behavior.
CONCLUSIONS: To reduce the risk of adolescent sexual activity, parents and communities should encourage youth in middle school, especially females who experience early menarche, to delay serious romantic relationships.