Sample’s characteristics (n = 728).

Background
While the existence of a complex variety of casual sexual relationships (CSRs) has been acknowledged, studies rarely describe the prevalence of condom use across these relationships or how their hybrid nature, specifically relationship characteristics, affect condom use. This study aims to describe condom use within committed relationships and various types of casual sexual relationships (CSRs), examining the influence of relationship characteristics on condom use among culturally validated relationship types (committed, friends with benefits, hookups, booty call).
Methods
Emerging adults (N = 728, 18–29 years, M = 22.56; SD = 3.01) completed a survey with four blocks: sociodemographics; brief sexual history; relationships over the previous year; and current relationship, assessing relationship type, ten relationship characteristics (e.g., commitment, emotional and sexual exclusivity, partner acquaintance, sexual involvement) and condom use (vaginal, oral, and anal), operationalized by three measures (use at last encounter, likert-type scale and percentage of use).
Results
The results showed patterns in condom use by relationship type and illuminated how relationship characteristics—grouped into three factors: commitment, intimacy, and sexuality—mediate condom use. Condom use was more frequent in vaginal than anal and oral sex, and less frequent in committed relationships. No significant differences were found in condom use in vaginal sex between committed relationships and hookups, with condom in these relationships being significantly lower than in booty call. Intimacy mediated between all contrasts tested and condom use in vaginal sex, while sexuality mediated between committed vs. CSRs and condom use in anal and oral sex.
Conclusions
Findings point to the need of considering the diversity of CSRs for understanding condom use and highlight the role of intimacy as a relevant mechanism associated with condom use in vaginal sex and of sexuality in oral and anal sex, which should be taken into consideration in the tailoring of health promoting efforts.

背景
尽管学界已认可存在种类繁杂的临时性性关系（casual sexual relationships, CSRs），但现有研究极少描述此类关系中安全套使用的流行情况，也未探讨其混合属性——尤其是关系特征——如何影响安全套使用行为。本研究旨在描述承诺型亲密关系（committed relationships）与各类临时性性关系（CSRs）中的安全套使用情况，同时检验经文化验证的关系类型（承诺型亲密关系、炮友关系（friends with benefits）、约炮关系（hookups）、随叫随到性伴侣关系（booty call））中，关系特征对安全套使用的影响。
方法
本研究纳入728名成年初显期个体（emerging adults），年龄范围为18至29岁，平均年龄M=22.56，标准差SD=3.01。所有参与者完成了包含四个模块的调查问卷：社会人口学特征模块、简要性行为史模块、过去一年亲密关系情况模块以及当前亲密关系模块。问卷评估了关系类型、10项关系特征（如承诺程度、情感与性排他性、伴侣熟识程度、性卷入程度）以及安全套使用情况（涵盖阴道性交、口交与肛交），并通过三项指标对安全套使用进行操作化定义：最近一次性接触时的安全套使用情况、李克特量表（likert-type scale）评分及安全套使用比例。
结果
研究结果揭示了不同关系类型下的安全套使用模式，并阐明了归为承诺、亲密与性三个维度的关系特征如何对安全套使用发挥中介效应。结果显示，阴道性交中的安全套使用频率高于肛交与口交，而承诺型亲密关系中的安全套使用频率最低。承诺型亲密关系与约炮关系（hookups）在阴道性交安全套使用上无显著差异，但二者的安全套使用频率均显著低于随叫随到性伴侣关系（booty call）。亲密维度在所有检验的对比与阴道性交安全套使用之间发挥中介效应，而性维度则在承诺型亲密关系与临时性性关系（CSRs）的对比，以及肛交、口交中的安全套使用之间发挥中介效应。
结论
本研究结果表明，理解安全套使用行为需考虑临时性性关系（CSRs）的多样性；同时凸显了亲密维度在阴道性交安全套使用中的关联机制作用，以及性维度在口交与肛交安全套使用中的关联机制作用，上述发现可为定制化健康促进干预措施提供重要参考依据。