Daily associations between alcohol and sexual behavior in young adults

We tested within-person effects of alcohol on sexual behavior among young adults in a longitudinal burst design (N = 213, 6,487 days) using data collected from a previously published parent study. We differentiated effects of alcohol on likelihood of sexual activity versus use of protection against sexually transmitted diseases (STDs) or pregnancy on intercourse occasions by testing a multilevel multinomial model with 4 outcomes (no sex, oral sex without intercourse, protected intercourse, and unprotected intercourse). At the within-person level, effects of alcohol were hypothesized to be conditional upon level of intoxication (i.e., curvilinear effect). We also tested effects of four between-person moderators: gender, typical length of relationship with sexual partners, and two facets of self-control (effortful control and reactivity). Consistent with our hypothesis, low-level intoxication was associated with increased likelihood of engaging in oral sex or protected intercourse (relative to no sex) but was not related to likelihood of unprotected intercourse. The effect of intoxication on unprotected versus protected intercourse was an accelerating curve, significantly increasing likelihood of unprotected intercourse at high levels of intoxication. Between-person factors moderated associations between intoxication and sexual behavior. Effects of intoxication on both protected and unprotected intercourse were diminished for individuals with more familiar sexual partners. Effortful control exhibited a protective effect, reducing the effects of intoxication on likelihood of unprotected intercourse. Hypothesized effects of reactivity were not supported. Intoxication was a stronger predictor of oral sex and protected intercourse (but not unprotected intercourse) for women relative to men. Results highlight the inherent complexities of the alcohol-sexual behavior nexus.