Drivers with children in the car were less likely to drink but just as likely to test positive for THC | Research

The takeaway

In a Washington State roadside survey, drivers with child passengers were much less likely to have been drinking but equally likely to test positive for THC compared to drivers without children.

Parents who use cannabis, child safety advocates, and traffic safety policymakers.

14.1% of drivers with children tested positive for THC

What the researchers found

Drivers with children were less likely to be alcohol positive (0.2% vs. 4.5%, p < .0001) but equally likely to be THC positive (14.1% vs. 17.7%, p = .29). Among drivers who perceived no impairment risk from cannabis, 40.6% of those with a child and 28.9% of those without tested positive for THC.

Why it matters

Adults appear to self-regulate alcohol use when driving with children but do not similarly reduce cannabis use, possibly because they perceive cannabis as less impairing or less risky.

The numbers in context

2,056 drivers (1,238 male). Alcohol positive with child: 0.2%, without: 4.5%. THC positive with child: 14.1%, without: 17.7%. Among those perceiving no cannabis risk, 40.6% with a child tested THC positive.

How the study worked

Cross-sectional analysis of 2,056 drivers from the Washington State Roadside Survey (2014-2015). Oral fluid, blood, and breath samples collected to measure cannabis and alcohol. Self-reported data assessed risk perceptions.

What this study cannot tell us

Cross-sectional roadside survey; THC presence does not confirm impairment at the time of driving. Self-reported risk perceptions may not reflect actual behavior. Washington State may not generalize to other jurisdictions.

How to read the evidence

Moderate: systematic roadside survey with biological testing, but cross-sectional and unable to confirm actual impairment.

When this study was published

Published in 2019.

The bigger picture

This reveals a public health blind spot: while drunk driving with children has been heavily stigmatized, driving after cannabis use with children has not received the same attention, even in a state where cannabis is legal.

Questions still open

Would targeted messaging about cannabis-impaired driving with children change behavior? Why do risk perceptions for cannabis diverge so sharply from alcohol? Are children in THC-positive drivers' cars at measurably higher risk?

Common questions

Does testing positive for THC mean the driver was impaired?

Not necessarily. THC can remain detectable in biological samples long after effects have worn off. However, the study raises concerns about the frequency of recent cannabis use among drivers transporting children.

Why do drivers treat alcohol and cannabis differently?

Decades of public campaigns have stigmatized drunk driving, especially with children. Cannabis use while driving has not received the same level of public health messaging, and many users perceive it as less impairing.

Read the original research

Use of Alcohol and Cannabis Among Adults Driving Children in Washington State.

Journal of studies on alcohol and drugs, 80(2), 196-200

View on PubMed ↗

Citation

Romano, Eduardo; Kelley-Baker, Tara; Hoff, Staci; Eichelberger, Angela; Ramírez, Anthony. (2019). Use of Alcohol and Cannabis Among Adults Driving Children in Washington State.. Journal of studies on alcohol and drugs, 80(2), 196-200.