Condom use self-efficacy mediates chemsex and condom use: a moderated mediation analysis

Among men who have sex with men (MSM), chemsex is strongly associated with condomless anal sex, contributing to the increased burden of HIV and others sexually transmitted infections (STIs) in the community. In regions with limited accessibility to HIV pre-exposure prophylaxis, condoms remain a critical method for HIV prevention. However, there is a notable lack of research examining the impact of chemsex on condom use self-efficacy. This study aimed to examine condom use self-efficacy among chemsex users and to explore its interrelationship with chemsex and condomless anal sex. Adult MSM in Hong Kong were recruited in 2021. Logistic regression analysis was employed to explore factors associated with condomless anal sex, while mediation analysis was employed to examine the relationships among chemsex, condom use self-efficacy, and condomless anal sex. The analysis included 316 MSM, 51 (16.14%) of whom engaged in chemsex in the last three months, with significantly lower condom use self-efficacy scores. Multiple logistic regression analysis indicated that chemsex engagement was significantly associated with a higher likelihood of condomless sex. Mediation analysis showed that chemsex engagement indirectly increased the likelihood of condomless anal sex through its negative impact on condom use self-efficacy, with an odds ratio of 3.52 (95% CI: 2.12-7.09). Furthermore, sexual orientation was found to moderate this indirect effect. Among gay men, the indirect effect was more pronounced (odds ratio: 3.74, 95% CI: 2.20-7.71) compared to bisexual men (odds ratio: 2.01, 95% CI: 1.18-4.12). These findings highlight the importance of targeted interventions aimed at enhancing condom use self-efficacy among MSM, particularly among those engaging in chemsex. Strengthening self-efficacy may play a critical role in promoting condom use and reducing the risk of HIV and STIs in this population.