The contexts of sexual involvement and concurrent sexual partnerships.

CONTEXT: Concurrent sexual partnerships may facilitate the spread of STDs, but little is known about partnership concurrency and its association with the relationship contexts of sexual involvement.
METHODS: Data about demographic characteristics, sexual histories and the most recent opposite-sex partnership among 783 adults aged 18-59 were drawn from the 1995 Chicago Health and Social Life Survey. Wald chi-square tests assessed gender differences in the timing and type of sexual involvement and in concurrent partnerships; bivariate probit regression analyses examined associations between concurrent partnerships and sexual involvement and other characteristics.
RESULTS: One in 10 of both women and men reported that both they and their partners had had other partners. Men were more likely than women to have been nonmonogamous (17% vs. 5%), and women were more likely than men to report that their partner had been (17% vs. 8%). The probability of having been nonmonogamous was 44% higher among women who were sexually involved with a friend, and 30% higher among those with a casual partner, than among those in a serious relationship; the corresponding figures for their partners were 48% and 32%, respectively. For men, the probability of having been nonmonogamous was elevated by 25% among those who were sexually involved with a friend and by 43% among those with a casual partner; for their partners, the figures were 27% and 24%, respectively.
CONCLUSIONS: Increased awareness that nonromantic sexual involvement is associated with partnership concurrency may enhance individuals' understanding of the risks and rewards of their relationships.