The Canadian underage substance use prevention (CUSP) trial: Amended protocol for a hybrid...

Adolescent substance use remains a significant public health concern, particularly among youth with elevated personality-based risk profiles. PreVenture is a brief, personality-targeted intervention shown to reduce substance-related behaviours in prior randomized trials.

The Canadian Underage Substance Use Prevention (CUSP) trial was designed to evaluate the effectiveness and implementation of PreVenture under routine school conditions.

CUSP is a three-arm, parallel-group, hybrid effectiveness-implementation cluster randomized controlled trial in public secondary schools across three Canadian provinces. Schools were randomized to: (1) PreVenture via a Train-the-Trainer model; (2) PreVenture Train-the-Trainer plus Implementation Facilitation; or (3) treatment-as-usual control. Grade 10 students completed baseline screening using the Substance Use Risk Profile Scale (SURPS); those scoring above predefined SURPS thresholds were invited to participate in PreVenture workshops and included in primary analyses. The primary outcome is screening positive for substance-related problems (CRAFFT score ≥ 2). Secondary outcomes include binge drinking, cannabis, illicit drug, and non-medical prescription drug use. Implementation outcomes include fidelity, reach, uptake, acceptability, and sustainability.

Data collection is complete, but outcome analyses have not yet been conducted. The trial was affected by the COVID-19 pandemic and other implementation challenges, resulting in substantial attrition at both the student and school levels. This protocol documents modifications to the design and analytic plan, also reflected in the updated trial registration (NCT04198974), to ensure transparent reporting of findings. The pre-specified Statistical Analysis Plan, provided as an online supplement, was finalized and accepted by the trial steering committee prior to unblinding.

NCT04198974.