Study protocol for a cluster randomised controlled trial of The Illicit Project, a digital, neuroscience-based substance use intervention for secondary school students

Older adolescence (16–19 years) is characterised by an increase in alcohol and illicit substance use, however limited age-appropriate prevention programs exist to target this critical group. Schools are increasingly opting for web-based programs to deliver health education due to their effectiveness, accessibility and scalability. This study outlines the web-based adaptation of a neuroscience-based harm reduction program targeting older adolescents known as, The Illicit Project, and the study protocol to evaluate its effectiveness. A cluster randomised controlled trial will be conducted with Year 10, 11 and/or 12 students (aged 16–19 years) from 8 secondary schools across New South Wales, Australia. Participating schools will be randomised into the control group (health education as usual) or the intervention group (The Illicit Project program; a three-lesson, web-based program delivered fortnightly over 6 weeks) and will complete four web-based assessments at baseline, 6-, 12- and 24-months post baseline. Primary outcomes are the quantity and frequency of substance use, alcohol-related harms and drug literacy levels, with the 12-month follow-up, the primary end point. Secondary outcomes include intentions to use alcohol and other drugs in the future and risk perceptions. This trial has been registered with Australia and New Zealand Clinical Trials Registry (ACTRN12620000805976). Intervention effects will be estimated using multilevel mixed effects models with an intention-to-treat sample. This is the first evaluation of a web-based, age-appropriate neuroscience-based prevention program for substance use targeting older adolescents.