Background: Youth with alcohol or marijuana dependence or disorders (substance use disorders [SUDs]) are at increased risk of acquiring sexually transmitted diseases (STDs). Sexual partner characteristics may explain the relationship between SUD and STD.
Methods: Clinical criteria for SUD, clinical STD diagnosis, and sexual partner characteristics were assessed among 15- to 24-year-old STD clinic attendees between 1999 and 2002 (n = 412). We used exact logistic regression and path analysis to examine the mediation effect of sexual partner characteristics (age discordance, incarceration, STD diagnosis, other partners, perceived alcohol problem, perceived marijuana problem, and a calculated composite measure) on the relationship between SUD and STD, adjusting for important demographics and condom use.
Results: We found evidence of mediation by partner characteristics on the relationship between SUD and STD. For the logistic regression analysis, adding the partner characteristic composite reduced the strength of the association between SUD and STD from a statistically significant odds ratio of 1.7 (95% confidence interval = 1.0-2.7) to a statistically nonsignificant odds ratio of 1.5 (95% confidence interval = 0.9-2.5). In the path analysis, adding the partner characteristic composite reduced the significant direct effect of SUD on STD (β = 0.5, P = 0.04) to statistically nonsignificant effect (β = 0.1, P = 0.2). We estimated that 31% of the total effect of SUD on STD was attributable to the indirect path through the composite partner characteristic measure.
Conclusions: Even when controlling for demographics and condom use, partner characteristics partially explained the association between SUD and STD.