Half of college students regularly consume alcohol each month (Center for Behavioral Health Statistics and Quality CBHSQ, 2024b). Between 50 % and 70 % of college SA involves alcohol use by the perpetrator, victim, or both (Koss et al., 2022). Consuming alcohol does not cause SA – perpetrators of SA target individuals who are drinking because they may appear to have reduced awareness, impaired physical ability, or seem more isolated; yet responsibility for SA is always 100 % with perpetrators (Abbey, 2023, Recalde-Esnoz et al., 2024). Recently prevention efforts to address alcohol and SA have begun to integrate content rather than pursue separate interventions for each (Leone et al., 2022, Rizzo et al., 2023, Tibbels and Benbouriche, 2024). One of the first theory-driven and evidence-based interventions to integrate these topics is Positive Change© (Gilmore 2015; Gilmore 2022). Through focusing on the shared risk factor of alcohol use, Positive Change© targets not only negative alcohol-related consequences but also SA-related behaviors including victimization risk, perpetration, and bystander intervention. While preliminary direct effects of Positive Change© on alcohol use are documented elsewhere (see Gilmore 2015; Gilmore 2024); indirect effects which may be mediated through reductions to alcohol use have not yet been examined. Testing theorized intervention effect mechanisms is critical at this time when SA programs are considering ways to integrate alcohol-related material (Leone et al., 2022). In the current study we examine the indirect effects of Positive Change© on SA victimization and alcohol-related consequences through the mediating variable of weekly alcohol consumption.

About 7 % of college students engage in heavy episodic drinking, defined as four or more drinks for women and five or more drinks for men in less than 2 h (Center for Behavioral Health Statistics and Quality CBHSQ, 2024b). Experiences of alcohol-related consequences, such as passing out, decreased performance in class or schoolwork, and disrupted social relationships with peers, are reported to some degree by a majority of college students who consume alcohol, but students who engage in heavy drinking are 2–4 times more likely to experience these consequences (Patrick et al., 2020). Consuming alcohol pharmacologically contributes to these outcomes through decreased reaction time or ability to maintain focus. Consequences of drinking can also linger after consumption ceases, including nausea, feeling dehydrated, disoriented, and full/partial memory loss about events that occurred while drinking; these are also more likely to occur among students who engage in heavy drinking(Patrick et al., 2020).

SA perpetrators are also more likely to target individuals who are consuming alcohol or appear intoxicated (Abbey, 2017, Chopin and Beauregard, 2022, Mouilso and Wilson, 2019). For example, heavy drinking college students are more likely to frequent social drinking contexts such as bars where there is greater risk of victimization because potential perpetrators are more often present in those spaces (Hayes and Maher, 2024, Marcantonio et al., 2024, Peterson et al., 2023). Intoxication also increases likelihood of SA perpetration which would in turn increase the potential risk posed to others from intoxicated perpetrators present in social drinking spaces (Cleveland et al., 2019, Crane et al., 2016). The immediate pharmacologic effects of alcohol consumption may also increase one’s risk of being targeted by SA perpetrators (Spencer et al., 2024, Testa, 2023). Alcohol myopia narrows attentional focus onto salient cues and can reduce one’s ability to interpret and attend to SA risk cues (Baltariu et al., 2023, Melkonian and Ham, 2018, Steele and Josephs, 1990). Students who engage in heavy drinkingare at even greater risk of alcohol-involved SA victimization where the perpetrator(s), victim, or both consumed alcohol (Recalde-Esnoz et al., 2024).

Alcohol-involved SA is associated with more severe assaults, meaning the perpetrator is more likely to inflict physical injuries, there are likely multiple perpetrators, and survivors report a greater perceived threat of death and increased posttraumatic stress symptoms, depression, and suicidal ideation afterwards (Abbey et al., 2022, Ison et al., 2024). Larger quantities of alcohol can lead to partial or full physical incapacitation which SA perpetrators would target as a potential victim who is less able to resist, engage in self-defense, or seek help from bystanders nearby (Abbey et al., 2022, Melkonian and Ham, 2018, Sontate et al., 2021). College social drinking spaces are also likely to have fewer capable bystanders, as individuals who frequently consume alcohol report lower intentions to intervene in SA situations (Rizzo et al., 2023). In sum, heavy drinking college students are at heightened risk for not only alcohol-related consequences but also at heightened risk to be targeted by perpetrators as potential SA victims and experiencing more severe SA.

Positive Change© was designed specifically for heavy drinking college students. The first version adapted the highly Web-BASICS (Larimer et al., 2023) into a combined SA victimization risk and alcohol use reduction personalized normative feedback intervention (PFI) (LaBrie et al., 2013, Larimer et al., 2023). A PFI directly compares participant’s own behavior/belief with the actual behaviors/beliefs reported by their peers. Positive Change© tailors feedback based on gender identity and sexual orientation. The SA risk reduction content empowers individuals to engage in protective strategies to reduce risk of alcohol-related consequences and SA victimization while placing the full responsibility of SA on the perpetrator (Gilmore 2022).

A randomized controlled trial (RCT) of the first Positive Change© conducted with college women who engaged in heavy episodic drinking (n = 207) decreased drinking to cope with anxiety, heavy episodic drinking, blackouts, and SA victimization and SA severity for women with more severe SA histories (Gilmore 2015, Gilmore 2016, Gilmore 2018). This RCT also established that the combined intervention had a greater impact on both alcohol- and SA-related outcomes than either component individually (Gilmore 2015).

The second version of Positive Change© (the focus of the current study) integrated additional content on SA perpetration prevention and SA bystander intervention from an evidence-based program for college men (Orchowski et al., 2016, Orchowski et al., 2018). An open pilot study (n = 24) of Positive Change© reduce descriptive drinking norms and increased awareness of SA victimization risk (Gilmore 2022). Participants also rated Positive Change© to have acceptable usability. A pilot RCT with college students (n = 165) found that this version of Positive Change© reduced SA victimization and showed downward trends for alcohol use (Gilmore 2024). A mediation analysis of the first Positive Change© effects on SA victimization found some mediation by hazardous alcohol use behaviors such as incapacitation and blackouts (Gilmore 2018), but no investigation of program mechanisms operating through alcohol use has yet been conducted for the second version.

Alcohol use is targeted in multiple ways in Positive Change© (Gilmore 2022). Participants receive feedback about social norms discussing their own drinks per week, perceptions of typical peers (matched by gender and sexual orientation) at their university, and actual drinks per week reported by peers. Content on alcohol myopia includes personalized blood alcohol concentration (BAC) charts and examples at different BAC levels highlighting how cognitive abilities supporting judgement and the perception of social cues can be impaired when intoxicated. Participants learn about and choose protective behavioral strategies to reduce potential harm from alcohol-related consequences stemming from alcohol use which they then practice in short scenarios. While some SA victimization risk reduction content is presented as its own focus, much of the material is fully integrated into the discussion of alcohol use and the intersection of the two topics. For example, the animated risk scenarios to practice active resistance strategies are set in drinking situations. At different BAC levels, examples are provided of how SA risk perception might be impaired by intoxication. The impact of the program may therefore reduce both alcohol use generally and SA victimization risk as it relates to alcohol use as well. Although more programs beyond Positive Change© have begun including alcohol use content alongside SA prevention content, the effect of addressing alcohol use behaviors in SA prevention programs is still largely unexamined.

Understanding whether and how a brief web-based intervention such as Positive Change© reduces drinking and in turn may affect consequences and SA risks associated with alcohol use is critical as the field searches for effective means to address these intertwined public health issues in resource and time-efficient ways. A prior study on the main effects of Positive Change© found participation had a significant direct effect reducing SA victimization and drinks per week at follow-up (Gilmore 2024). Building from those findings, the goal of the present study is to examine the potential mediating role of drinks per week for Positive Change©’s reduction of SA victimization and alcohol-related consequences (not previously examined). We hypothesized (H1) that drinks per week at 3-month follow-up (T2) will mediate the effect of Positive Change© on alcohol-related consequences at follow-up, i.e., we anticipated that Positive Change© participation would significantly reduce drinks per week and thereby more substantially reduce alcohol-related consequences. Similarly, we hypothesized that drinks per week at follow-up will mediate the effect of Positive Change© participation on (H2) SA likelihood at follow-up and (H3) SA severity at follow-up.