Joining forces: Developing a smoking prevention intervention in social work organisations through co-creation with adolescents and youth workers.

• The Double Diamond Model and the Intervention Mapping Protocol emerge as valuable tools for guiding and structuring a co-creation process with the aim of developing a health promotion intervention. • Collaborating with youth workers was important for facilitating access to adolescents, leveraging their trustful relationships and profound understanding of dynamics within youth social work organisations. • Integrating contextualised insights, provided by adolescents and key stakeholders, with theory- and evidence-based information can optimise smoking prevention interventions. • The co-creation process culminated in the KickAsh!-intervention, emphasising creative elements with the expectation of yielding impactful and effective outcomes. Adolescents experiencing societal vulnerability confront a higher risk of smoking initiation, thereby perpetuating health disparities. To develop a smoking prevention intervention tailored to these adolescents, employing a participatory approach such as co-creation with adolescents and key stakeholders can ensure alignment with their needs. Navigating a co-creation process, especially concerning a sensitive topic like smoking, remains uncharted territory in existing literature, particularly when engaging with hard-to-reach youth. This paper describes the co-creative process underpinning the KickAsh!-intervention, a smoking prevention program involving youth workers and 10–15-year-olds experiencing societal vulnerability. Four youth workers (M age = 23.75 ± 0.96 years) and nine adolescents (M age = 13.56 ± 0.73 years) from two social work organisations in Ghent, Belgium, participated in an eight-month co-creation trajectory together with two academic researchers and one design thinking specialist. The Double Diamond Model (DDM) and the Intervention Mapping Protocol (IMP) facilitated this trajectory. The objectives and working methods from each co-creation session are described. The outcomes of each co-creation session and how these findings have shaped the development of the KickAsh!-intervention – a comprehensive website consisting of materials developed in collaboration with youth workers and adolescents – are described. This paper emphasises the value of prioritising participatory designs (such as DDM) structured by a theory- and evidence-based framework for intervention development (such as IMP). This approach enabled us to devise intervention strategies rooted in the lived experiences of adolescents and youth workers, ensuring practicality within the given context. The developed KickAsh!-intervention closely aligns with the preferences of both adolescents and youth workers. It prioritises creative elements informed by theory and scientific evidence with the expectation of achieving impact. However, further research is needed to evaluate the effectiveness of the KickAsh!-intervention. [ABSTRACT FROM AUTHOR]