A behavioral decision model testing the association of marijuana use and sexual risk in young adult women.

We created a model conceptualizing sexual risk as a series of discrete event-specific behavioral decisions and tested the hypothesis that marijuana use was associated with increased sexual risk-taking. Three hundred eight marijuana-using women aged 18-24 completed a 90-day time-line-follow-back to assess sexual behaviors and marijuana use. A sequential logit model estimated the effect of marijuana use on the likelihood of being sexually active, partner type when sexually active, and condom nonuse conditional on partner type. Participants had a mean age of 20.4 years, with 67% Caucasian. Marijuana use was associated with an increased likelihood of being sexually active (OR 1.6; 95% CI 1.33, 1.93) and with condom nonuse when sexually active with casual partners (OR 2.58; 95% CI 1.1, 6.09). This behavioral decision model identified where marijuana use affected sexual risk, and suggests where interventions designed to reduce risk may have an impact.