Effectiveness of a neuroscience-based, harm reduction program for older adolescents: A cluster randomised controlled trial of the Illicit Project

The prevention of risky adolescent substance use is critical. Limited age-appropriate, school-based programs target adolescents aged 16–19 years, despite this representing the age of initiation and escalation of substance use. The Illicit Project is a neuroscience-based, harm reduction program targeting late adolescents, designed to address this gap. The current study aims to evaluate the program’s effectiveness in reducing risky substance use and related harms among late adolescents. A cluster randomised controlled trial was conducted involving 950 students (M(age) = 15.9 years SD = 0.68; 60% Female) from eight secondary schools in Australia. Five schools received The Illicit Project program, and three schools were randomised into the active control group (health education as usual). All students completed a self-report survey at baseline and 6-months post-baseline and intervention students completed a program evaluation survey. Outcomes include alcohol and substance use, alcohol related harms and drug literacy levels (knowledge and skills). At 6-months post baseline, individuals in the intervention group were less likely to engage in weekly binge drinking (OR = 0.56), high monthly alcohol consumption (OR = 0.56), early onset cannabis use (OR = 0.35), risky single occasion cannabis use (OR = 0.48), MDMA use (OR = 0.16) or nicotine product use (OR = 0.59) compared to the control group. Students in the intervention group were less likely to have experience alcohol related harms (OR = 0.57) and more likely to have higher drug literacy scores (β = 2.44) at follow-up. These preliminary results support the effectiveness of The Illicit Project. Further follow-up is required to determine the durability of the results over time.