Canadian teens who used both alcohol and cannabis were 9.5 times more likely to ride with an impaired driver than alcohol-only users | Research

The takeaway

Among nearly 70,000 Canadian secondary school students, dual use of alcohol and cannabis was associated with 9.5 times higher odds of riding with someone impaired by both substances, with nearly half of dual users reporting impaired driving or riding exposure.

Road safety program designers; school-based prevention coordinators addressing impaired driving among youth.

49.6% of dual users reported impaired driving exposure

What the researchers found

Overall, 14.7% of students reported impaired driving or riding (IDR). Prevalence varied dramatically by substance use: 8.0% nonusers, 21.9% alcohol-only, 35.9% cannabis-only, and 49.6% dual users. Dual use was associated with 9.5 times higher odds of alcohol-cannabis IDR compared to alcohol-only use, and 3.0 times higher odds compared to cannabis-only use.

Why it matters

This is one of the largest studies to quantify impaired driving exposure among teens using both alcohol and cannabis. The near-50% IDR prevalence among dual users represents a major road safety concern, especially as both substances become more accessible.

The numbers in context

69,621 students in 182 schools. IDR prevalence: 8.0% nonusers, 21.9% alcohol-only, 35.9% cannabis-only, 49.6% dual use. Dual vs alcohol-only IDR: OR 9.5. Dual vs cannabis-only: OR 3.0. Gender diverse students, older students, and lower SES associated with higher IDR.

How the study worked

Cross-sectional survey of 69,621 students in 182 Canadian secondary schools during the 2021/22 school year. Multilevel logistic regression accounting for school clustering. Interactions tested for gender and age.

What this study cannot tell us

Cross-sectional design. Self-reported substance use and IDR. Cannot determine the specific IDR situations (e.g., who was driving, relationship to driver). Single school year. Canadian context may differ from other countries.

How to read the evidence

Very large school-based survey with multilevel analysis accounting for clustering. Cross-sectional design limits causal inference.

When this study was published

2024 study

The bigger picture

The finding that even nonusers report 8% IDR prevalence means all students are at risk from impaired drivers, but dual substance users face disproportionate danger. Road safety interventions should specifically address the combined use scenario.

Questions still open

Are safe ride programs accessible to teens in dual-use scenarios? How do teens perceive the combined impairment risk of alcohol plus cannabis?

Common questions

Why is dual use more dangerous for driving?

Alcohol and cannabis impair driving through different mechanisms (alcohol affects reaction time and judgment; cannabis affects attention and lane-keeping). Combined impairment is greater than either substance alone, and users may underestimate the combined effect.

Does this mean all substance-using teens drive impaired?

The study measured impaired driving OR riding with an impaired driver. Many of the teens were passengers, not drivers. However, both situations put teens at risk of traffic injury.

Read the original research

The association between single and dual use of cannabis and alcohol and driving under the influence and riding with an impaired driver in a large sample of Canadian adolescents.

Traffic injury prevention, 25(6), 765-773

View on PubMed ↗Publisher’s paper ↗

Citation

Gohari, Mahmood R; Patte, Karen A; Elton-Marshall, Tara; Cole, Adam; Turcotte-Tremblay, Anne-Marie; Bélanger, Richard; Leatherdale, Scott T. (2024). The association between single and dual use of cannabis and alcohol and driving under the influence and riding with an impaired driver in a large sample of Canadian adolescents.. Traffic injury prevention, 25(6), 765-773. https://doi.org/10.1080/15389588.2024.2342571