Event-level effects of alcohol, cannabis, and simultaneous alcohol and cannabis use on bystander intentions in response to hypothetical situations among college women

Bystanders can play an important role in preventing alcohol-related harm (e.g., unintentional injury) or sexual aggression. While the impact of one's own acute alcohol intoxication on sexual aggression bystander intervention has been explored, less is known about how alcohol impacts the ability to intervene in alcohol-related harm. Further, scant research has examined one's own cannabis or simultaneous alcohol and cannabis use (i.e., using alcohol and cannabis at the same time so that their effects overlap) on bystander intervention. The present study employed an ecological momentary assessment (EMA) to test the acute effects of alcohol and cannabis on intentions to intervene in (1) alcohol-related harm and (2) sexual aggression. Participants were 81 U.S. college women aged 18 to 24 who engaged in heavy episodic drinking, cannabis, and simultaneous use in the past month. Participants completed an identical report delivered at random times on two evenings assessing acute alcohol and/or cannabis use and then responded to questions assessing bystander intentions to prevent alcohol-related harm and sexual aggression in a hypothetical party situation. Acute alcohol and simultaneous use, compared to no substance use, was associated with fewer intentions to intervene in alcohol-related harm and in sexual aggression. Results highlighted the nuanced impact of alcohol, cannabis, and simultaneous use on bystanders and can help inform bystander training programs for both alcohol-related harm and sexual aggression.