Cluster randomised controlled trial of an online intervention to prevent ecstasy and new psychoactive substance use among adolescents: final results and implications for implementation

Objectives To evaluate the effectiveness of the online Climate Schools: Ecstasy and Emerging Drugs module over 2years, and examine the impact of intervention dose on outcomes. Design Cluster randomised controlled trial. Setting Secondary schools in Australia. Participants 1126 students (aged 14.9 years) from 11 schools. Intervention Five schools were randomly allocated to the four-lesson internet-based Climate Schools: Ecstasy and Emerging Drugs module. This universal intervention uses cartoon storylines to deliver harm-minimisation information about ecstasy and new psychoactive substances (NPS). It was delivered during health education classes over 4weeks. Six schools were randomised to the control group (health education as usual). Participants were not blinded to intervention allocation. Outcomes measures Students completed self-report surveys at baseline, post-test, 6, 12 and 24months post-baseline. Intentions to use ecstasy and NPS (including synthetic cannabis and synthetic stimulants), knowledge about ecstasy and NPS and lifetime use of ecstasy and NPS were assessed. This paper reports the results at 24months post-baseline. Analysis Mixed effects regressions were conducted to analyse intervention effects from baseline to 24months. Post hoc analyses using Inverse Probability of Treatment Weighting compared controls with students who: i) completed all four lessons (full dose') and ii) partially completed the intervention (three lessons, incomplete dose'). Results Primary analyses found that controls were significantly more likely to intend on using synthetic cannabis compared with intervention group students (OR=3.56, p=0.01). Results from the weighted analyses indicated that controls reported significantly lower knowledge about ecstasy (p=0.001) and NPS (p=0.04) compared with the full-dose group. No significant differences were observed between the incomplete dose and control groups. Conclusions The online intervention was effective in modifying students' intentions to use synthetic cannabis up to 24months; however, this study highlights the importance of delivering prevention programmes in full to maximise student outcomes. Trial registration number ACTRN12613000708752.