Preliminary efficacy of ‘high-alert’ a brief smartphone intervention to reduce Cannabis-impaired driving among youth: A pilot randomized controlled trial

Driving under the influence of cannabis (DUIC) is a growing public health concern, particularly among young drivers. This pilot study explores the short-term preliminary efficacy of High Alert, a brief smartphone intervention designed to reduce DUIC among youth. An online pilot randomized controlled trial was conducted with 102 youth aged 18–24 who had a history of DUIC (≥3 times in the past 3 months). Participants were randomized into three groups: High Alert (n = 37), Active Control (n = 34), or Passive Control (n = 31). High Alert included two web-based sessions on cannabis and DUIC education. The Active Control received a single session reviewing six DUIC-related infographics, while the Passive Control received no intervention. The primary outcome was self-reported DUIC incidents (alone or with other substances) over 3 months, assessed at baseline and 3-month follow-up. Among the 52 participants who completed the 3-month follow-up (High Alert: n = 16; Active Control: n = 16; Passive Control: n = 20), High Alert showed the greatest mean reduction in DUIC incidents (-7.44, Cohen’s d = -0.40), compared to Active Control (-3.62, d = -0.49) and Passive Control (-3.05, d = -0.38). The reduction was statistically significant compared to Passive Control (β = -0.61, p = .03), but not Active Control (β = -0.08, p = .781). Preliminary findings suggest that High Alert may show promise in reducing self-reported DUIC behaviours compared to a no-contact control group, but additional research with larger samples and longer follow-ups is needed. ClinicalTrials.gov registration NCT06098573 . • Digital interventions are popular for cannabis use and impaired driving prevention. • The study tested a brief smartphone intervention via a pilot 3-arm randomized trial. • Participants were high-risk youth 18 to 24 who frequently drive after cannabis • The intervention reduced youth cannabis-impaired driving compared to the control.