From Daily Attitudes to Alcohol‐Related Harm: A Within‐Person Serial Mediation Test Informed by the Theory of Planned Behavior

BACKGROUND: The Theory of Planned Behavior (TPB) posits that attitudes influence behavior through intentions, yet this pathway has not been thoroughly examined at the within-person level in the alcohol literature. This study tested whether daily fluctuations in attitudes toward heavy drinking predicted same-day alcohol-related consequences and alcohol-induced blackouts through a serial mediation involving daily drinking intentions and alcohol consumption. METHODS: Participants were 87 heavy-drinking young adults (53.4% female; Mage = 22.22 years) enrolled in the intervention arm of a randomized clinical trial who completed up to 30 consecutive days of morning diary assessments. Multilevel models separated within-and between-person variance by person-mean centering daily predictors. Serial mediation pathways were estimated using multilevel regression models, and specific indirect effects were tested using Monte Carlo confidence intervals. RESULTS: On days when participants reported more favorable attitudes toward heavy drinking than their own average, they also reported stronger intentions to drink, which predicted greater same-day alcohol consumption. Greater drinking, in turn, predicted increased odds of both alcohol-related consequences and blackout. Significant serial indirect effects supported the hypothesized pathway from attitudes to consequences and blackout through intentions and drinking. Drinking intentions also directly predicted alcohol-related consequences independent of drinking quantity but did not directly predict blackout after accounting for drinking, suggesting differences in the mechanisms underlying these outcomes. CONCLUSION: Findings provide day-level support for a TPB-informed pathway linking within-person fluctuations in drinking attitudes to alcohol-related harm through drinking intentions and alcohol consumption. Results extend prior between-person TPB research by demonstrating that attitudes and intentions function as dynamic, day-to-day processes that help explain when individuals are at elevated risk for harmful drinking outcomes. Daily attitudes and intentions may represent promising targets for ecological momentary interventions designed to reduce alcohol-related harm.