Abstract
Background: Vocational school students exhibit a high prevalence of addictive behaviors. Mobile phone–based prevention
programs targeting multiple addictive behaviors and promoting life skills are promising. Tailoring intervention content to
participants’ preferences, such as allowing them to choose behavior modules, may increase engagement and efficacy. There is
limited understanding of how personal characteristics relate to module choices.
Objective: This study examined the prevention needs of German vocational school students as well as their prevention preferences
through self-determined module choice in the multibehavior app-based addiction prevention program ready4life.
Methods: A 2-arm cluster randomized controlled trial recruited German vocational school students aged ≥16 years. Among
376 classes from 35 schools, ready4life was introduced during a school lesson. Students were invited to download the ready4life
app and completed an anonymous screening with individualized risk and competence feedback in the form of a traffic light
system. Informed consent was provided by 2568 students. Intervention classes received individual app-based coaching with
weekly chat contacts with a conversational agent over 4 months. They could choose 2 of 6 modules: alcohol, tobacco, cannabis,
social media and gaming, stress, and social competencies. Control group classes received a link to health behavior information
and could access coaching after 12 months.
Results: Prevention need was high. For 86.2% (2213/2568), ≥2 risks were reported based on yellow or red traffic light feedback.
Within the intervention group, stress (818/1236, 66.2%) and social media and gaming (625/1236, 50.6%) were the most chosen
topics, followed by alcohol (360/1236, 29.1%), social competencies (306/1236, 24.8%), tobacco (232/1236, 18.8%), and cannabis
(131/1236, 10.6%). Module choices closely aligned with received traffic light feedback among those with 1 or 2 risks. Multilevel
regression models showed that women were significantly more likely to choose the stress module (odds ratio [OR] 2.38, 95% CI