Importance: In the US, 25% of youths have a chronic medical condition (CMC). Alcohol use is prevalent among youths with a CMC and is associated with treatment nonadherence, simultaneous exposure to contraindicated medications, poor self-care, and elevated rates of progression to heavy and problem use by young adulthood. Preventive interventions targeting these youths are scarce and lack evidence about longer-term risk-stratified effects.

Question: Does exposure to a brief, self-administered, disease-tailored preventive intervention lead to reduced alcohol use after 12 months among youths with a chronic medical condition (CMC)?

Findings: This secondary analysis of a randomized clinical trial used data from 451 youths with a CMC. Among youths reporting high-risk alcohol use at baseline, there was a 40% relative reduction in alcohol use frequency among youths who received the intervention vs treatment as usual; no difference was observed among youths reporting no or low-risk use at baseline.

Meaning: The intervention reduced alcohol use among medically vulnerable youths reporting high-risk use, underscoring the value of using personalized prevention strategies and investigating effect heterogeneities over long periods.