Longitudinal analysis for between- and within-person influences of descriptive alcohol drinking norms and attitudes on drinking outcomes

Background: The study aimed to expand on existing research related to the theory of planned behavior (TPB) by exploring both between-person and within-person effects of descriptive norms and attitudes toward moderate and heavy drinking on drinking outcomes, including drinks per week, blackouts, and alcohol-related consequences. While previous studies focus on between-person effects, this study uniquely investigates both between-person effects as well as within-person changes over time, using longitudinal data collected at six points over 12 months. Methods: Participants included 484 mandated college students (M_age = 18.66, SD_age = 0.758; 55.6% male). Participants completed measures of descriptive drinking norms, attitude toward moderate and heavy drinking, drinking intentions, and drinking outcomes, including drinks per week, blackout, and alcohol-related consequences. Multilevel models were run to examine the unique between-and within-person effects of descriptive drinking norms and attitude toward moderate and heavy drinking on drinking outcomes. Results: Overall, the results from the multilevel models showed that at the between-person level, descriptive norms were associated with drinks per week, and a more favorable attitude toward heavy drinking was associated with higher weekly alcohol consumption and related consequences. At the within-person level, within-person fluctuations in descriptive norms and attitude toward heavy drinking were associated with higher weekly drinking, blackout, and alcohol-related consequences, while favorable attitude toward moderate drinking were associated with lower odds of blackouts and fewer alcohol-related consequences. Conclusions: Attitudes toward drinking, particularly heavy drinking, at both between-person and within-person levels, are strong predictors of alcohol use and its consequences. Furthermore, attitude toward moderate drinking are protective. Interventions promoting a moderate drinking attitude and reducing heavy drinking attitude and descriptive drinking norms will likely be effective in reducing alcohol-related harm.