Introducing a group-based cannabis prevention program for adolescents in youth residential care in Germany (CANJuStop): Study protocol for an exploratory randomized controlled trial

Background Adolescents living in residential youth care represent one of the most vulnerable groups within child and youth welfare systems. They frequently experience complex developmental challenges, including unstable family environments, traumatic experiences, and disrupted caregiving which may contribute to elevated rates of psychological distress, psychiatric disorders, and problematic cannabis use. Residential care staff report substantial burdens related to substance use among youth but have limited access to structured, evidence-based prevention tools. Existing prevention programs are largely school-based and not adapted to the organizational structures, routines, and relational dynamics of residential facilities. As a result, a substantial gap persists between youth welfare services and addiction prevention systems. Despite the clear need, systematically evaluated, target-group-specific prevention or early-intervention programs for adolescents in residential care remain scarce. This study aims to evaluate the feasibility and preliminary effectiveness of an adapted version of the evidence-based CAN Stop group program for reducing problematic cannabis use among adolescents in residential youth care. Methods/design This exploratory pilot study uses a cluster-randomized controlled trial with two parallel arms: an intervention group receiving the adapted CAN Ju Stop program and a waitlist control group. Clusters—defined as residential care units—are randomized at the group level. Assessments take place in both groups at baseline (t ₀ ), post-intervention (t ₁ ) and six-month follow-up (t ₂ ). Adolescents aged 12–21 years living in residential youth care are eligible with informed consent; exclusion criteria are acute psychosis or acute suicidal ideation. CAN Ju Stop consists of six weekly sessions delivered by trained residential care staff and focuses on motivational enhancement, harm reduction, and coping skills. The primary outcome is the continued abstinence and/or meaningful reduction of cannabis use in the past 30 days, measured by self-report; secondary outcomes include problematic use patterns, refusal self-efficacy, and future use intentions. Discussion Findings from this study will help inform the development and implementation of a future RCT, should the CAN Ju Stop prevention program be feasible in residential youth care. Trial registration German Clinical Trials Register, DRKS-ID: DRKS00034167. Registered 13 May 2024, https://drks.de/search/en/trial/DRKS00034167