In Chile, the prevalence of tobacco, alcohol and drug use among adolescents is very high. Decades of research indicate that parenting interventions reduce these risky behaviors. However, there are no parenting interventions validated in Chile to prevent adolescent substance use. This article reports the development of the ¡Vamos por Mas! (¡VxM!) program following the recommendations of the Medical Research Council’s framework for designing and evaluating complex interventions. After identifying key intervention components, a preliminary version of a substance-use prevention program was designed. The preliminary intervention targeted families with adolescents in fifth and sixth grade and had four components: personalized feedback, in-person workshops, virtual engagement, and family support, to deliver positive-youth development and family-strengthening content. Then, students, guardians, school staff and community experts from different school systems (N = 111) evaluated the preliminary version of the program through a convergent parallel mixed methods study, including focus groups (N = 14) and surveys (N = 101). In general, all participants had positive perceptions of the program and valued its purpose, strategies, objectives and contents. Suggestions included expanding the purpose to promote healthy relationships, focusing on schools with low and intermediate socioeconomic vulnerability, including self-control content, removing the personalized feedback component and adding two additional components: school partnership and external supervision, among other improvements. With this information, the final version of the ¡VxM! program was developed. After a rigorous intervention development process, the ¡VxM! program is ready to be piloted and evaluated in a randomized trial.

Chile has high rates of tobacco, alcohol and drug use among adolescents. Parenting interventions have shown to reduce these risky behaviors. However, there are no parenting interventions validated in Chile to prevent adolescent substance use. This article reports the development of the ¡Vamos por Mas! (¡VxM!) program to strengthen family relations and prevent adolescent substance use following the recommendations of the Medical Research Council’s framework for designing and evaluating complex interventions. In the first phase, key intervention components were identified. Then, a preliminary version of the intervention was designed. In the second phase, perceptions of key stakeholders were collected through focus groups (N = 14) and surveys (N = 101) including adolescents, guardians, school staff and community experts. These participants evaluated the preliminary version of the program and provided feedback. In the final phase of the intervention development process, stakeholder opinions were integrated into the proposal. The final version of the ¡VxM! program included five components: (i) school partnership, (ii) in-person workshops, (iii) virtual engagement, (iv) family support and (v) external supervision. This version is ready to be piloted to evaluate feasibility and preliminary efficacy, before being assessed in a randomized trial.

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