Abstract: | We examined whether pre‐existing parent psychological distress moderated juvenile offenders’ substance use, sexual risk, and mental health outcomes in a randomized trial. Forty‐seven parent–adolescent dyads received either Family‐based Affect Management Intervention (FAMI) for adolescent substance use and HIV prevention or adolescent‐only Health Promotion Intervention (HPI). Parents’ self‐reported distress at baseline significantly moderated adolescents’ self‐reported marijuana use and alcohol use but not other outcomes at 3 months postintervention, producing crossover interactions. FAMI outperformed HPI when parents reported high‐level distress, whereas HPI outperformed FAMI when parents reported low‐level distress. This finding that the relative efficacy of interventions depends on the severity of parent psychological distress could inform efforts to match substance‐using, justice‐involved adolescents with the intervention most likely to benefit them. |