Within-Person Predictors of Same-Day Alcohol and Nonmedical Prescription Drug Use Among Youth Presenting to an Urban Emergency Department.

Objective: Simultaneous alcohol and nonmedical prescription drug use (NMPDU) increases acute risks (e.g., overdose) associated with each; understanding social, substance use, and mental health predictors of same-day use may suggest intervention targets.

Method: At an urban emergency department, research assistants recruited youth ages 14-24 reporting past-6-month substance use ( = 599; 58.8% male). Participants self-administered validated measures of alcohol consumption, cannabis use severity (quantity and consequences), mental health symptoms, and social influences at baseline and at four biannual follow-ups. In addition, participants completed Timeline Followback calendars that assessed same-day use of alcohol and prescription drugs. We used negative binomial regression with person-level fixed effects to isolate within-person predictor effects on same-day use frequency.

Results: Between 6.0% (baseline) and 8.6% (6-month follow-up) of youth reported same-day alcohol use and NMPDU across follow-ups. Within-person increases in alcohol consumption, cannabis use severity, and depression and anxiety symptoms all corresponded to greater same-day alcohol and NMPDU frequency, with consistent findings across genders. Increased positive peer behaviors corresponded to decreased same-day use frequency among males but not females. Decreased parental support and increased delinquent peer exposures corresponded to greater same-day use frequency among females but not males.

Conclusions: Substance use and mental health symptom escalation are robust predictors of greater same-day use frequency, whereas the roles of social factors appear gender-specific. Interrupting worsening trajectories of substance use and mental health symptoms, and enhancing social support and reducing delinquent peer exposures, may reduce same-day use frequency.