Youth demonstrate the highest rates of cannabis use and impaired driving, and drug-impaired driving continues to rise. The risks intensify when cannabis is combined with other substances, as polysubstance use significantly worsens driving impairment, elevates crash risk beyond single-substance use, increases DUIC engagement, and results in more severe legal consequences. Emerging research on smartphone-based brief interventions shows promise, with studies demonstrating their effectiveness in reducing alcohol-impaired driving, enhancing risk awareness, and decreasing DUIC behaviors among college students. Building on this evidence, the present study evaluates “High Alert,” a smartphone intervention designed to prevent youth DUIC by identifying potential design and implementation challenges while assessing its preliminary efficacy.
This study piloted the High Alert program using a three-arm randomized controlled design comparing the intervention with an active DUIC education control and a passive no-contact control among 18–24-year-old Ontario drivers who reported recent DUIC. Participants were stratified by sex and randomized 1:1:1 after baseline assessment. High Alert consisted of four brief interactive online modules delivered over two sessions, while the active control received static DUIC-related infographics. Outcomes were assessed at baseline and 3-month follow-up via online surveys. The primary outcome was past 3-month DUIC behavior, and the secondary outcome was risky cannabis use (CUDIT-R), with intervention effects analyzed using generalized linear mixed models under a per-protocol approach.
The final sample comprised 102 participants (High Alert: n=37; active control: n=34; passive control: n=31). High Alert demonstrated the largest mean reductions in both cannabis-only DUIC and total DUIC outcomes compared to control groups. High Alert significantly reduced total DUIC relative to the passive control, and post-hoc analyses revealed a significant difference between active and passive controls for total DUIC; however, differences between High Alert and the active control did not reach statistical significance. All participants reported high baseline levels of risky cannabis use (mean CUDIT-R scores exceeded the threshold for probable cannabis use disorder), and CUDIT-R scores decreased across all groups over time with no significant group-by-time interaction, indicating that reductions in risky cannabis use were not intervention-specific
Takeaway: The High Alert brief smartphone intervention was associated with reductions in total DUIC, suggesting potential as a DUIC prevention intervention for young drivers.