Individual and Social Factors Related to Trajectories of Blackouts among Underage Drinkers in the Emergency Department

Aims: Alcohol-related blackouts can result in acute injuries and other negative outcomes. Among underage risky drinkers, we examined longitudinal trajectories of blackout frequency following an emergency department (ED) visit, and identified baseline characteristics associated with blackout trajectory membership. Methods: Participants (ages 14-20; N = 836) attending an ED who screened positive for risky drinking and enrolled in a randomized-controlled trial of brief alcohol interventions were assessed at baseline, 3-, 6-, and 12-months. We used group-based trajectory modeling to determine characteristic trajectories of blackout frequency over 12-months in relation to baseline characteristics: demographics, substance use, delinquency, depression/anxiety symptoms, sexual assault, dating violence, and peer and sibling influences. Results: We identified four groups: No/Low blackouts (n = 248; 29.7%), Declining blackouts (n = 92; 11.0%), Moderate blackouts (n = 337; 40.3%) and High blackouts (n = 159; 19.0%); group membership did not differ based on intervention receipt. In adjusted analyses, compared to the No/Low group all other groups had higher odds of having an alcohol-related baseline ED visit. Female sex, alcohol consumption, prescription drug misuse, sexual assault while incapacitated due to substances, and negative peer influences were positively associated with membership in the High group; College/Greek life involvement was also highest. Negative peer influences and being in high school (vs. College/Greek life) also distinguished the Moderate group. Conclusion: Blackout frequency was largely stable over time and riskier trajectories were marked by risk factors such as negative peer influences and college/Greek life involvement. Findings may inform targeted interventions, particularly for women who were in higher risk trajectories.