Negative consequences associated with daily alcohol use as a nonlinear function of number of drinks in a daily diary study

Introduction: Drinking intensity among young adults is associated with greater negative alcohol-related consequences, but often studied using categorical drinking thresholds. This study examined how alcohol-related consequences varied as a continuous function of number of drinks consumed, without imposing thresholds, to identify drink ranges for which risk is greatest. Methods: Analyses included daily surveys from the Young Adult Daily Life study (2019–22) in which individuals reported drinking 1 or more alcoholic drinks (n=5219 days; 832 individuals). Time-varying effect models estimated total number of negative alcohol-related consequences and five individual consequences (hangover, drank more than planned, nausea/vomiting, did something embarrassing, blacked out) as a function of the number of drinks consumed among young adult males and females. Results: Often, increases in the number and prevalence of negative consequences were a nonlinear function of the number of drinks consumed. Females reported few negative consequences on 1-to-3-drink occasions but steep increases in consequences on 4-to-9-drink occasions. Among females, the prevalence of blacking out increased six-fold from 4-drink (3.4%; 95% CI=2.6,4.7) to 9-drink occasions (20.6%; 95% CI=16.1,26.1). Among males, the prevalence of some consequences, while not linear, increased across the full drink range. Blacking out among males increased from 9.6% (95% CI=6.2,14.7) on 10-drink occasions to 23.9% (95% CI=15.0,35.8) on 15-drink occasions. Conclusions: Substantial heterogeneity is missed when typical drinking categories are used. In particular, variability in consequences across levels of the traditional binge drinking category suggests that important differences in risk may be missed when assessed as a uniform category.