Factorial randomised controlled trial to examine the potential effect of a text message-based intervention on reducing adolescent susceptibility to e-cigarette use: a study protocol

Introduction Adolescent e-cigarette use, globally and within Australia, has increased in recent years. In response, public health agencies have called for the development of education and communication programmes targeting adolescents. Despite such recommendations, few rigorous evaluations of such interventions currently exist. The main objective of this study is to examine the potential effect of a text message intervention targeting parents and adolescents on adolescent susceptibility to e-cigarette use (eg, intentions towards using e-cigarettes). Secondary objectives are to (1): examine the effect of the intervention on adolescent e-cigarette and combustible tobacco use and (2) examine the acceptability of the intervention.Methods and analysis A randomised controlled trial employing a 2x2 factorial design will be conducted with parent-adolescent dyads (aged 12-15 years). Dyads will be randomly allocated to one of four arms: arm 1-a text message intervention delivered to adolescents only; arm 2-a text message intervention delivered to the parents of adolescents only; arm 3-a text message intervention delivered to both the parents and adolescents; and arm 4-an information only control, consisting of an e-cigarette factsheet provided to parents only. Participant recruitment commenced in March 2023 with the aim to recruit 120 parent-adolescent dyads. Data collection to assess study outcomes will occur at baseline, 6, 12 and 24 months post the commencement of the intervention. The primary endpoint will be 6-month follow-up. The primary outcome will be adolescent susceptibility to e-cigarette use, assessed using validated items. Analyses of trial outcomes will be undertaken under an intention-to-treat framework, with all participants included in the analysis in the group they were allocated.Ethics and dissemination Ethics approval has been obtained from the human research ethics committee of the University of Newcastle (H-2022-0340). Findings will be disseminated in peer-reviewed journals and at conferences.Trial registration number The trial was registered prospectively with Australian New Zealand Clinical Trials Registry (ACTRN12623000079640).