Occasional Cannabis Users Had the Worst Driving Impairment During Distraction Tasks
Occasional cannabis users were 3.7 times more likely to depart their lane during distracted driving after smoking, while daily users compensated by driving slower.
Quick Facts
What This Study Found
Occasional cannabis users (1-2 times/week) had significantly increased lane departure risk during distraction after acute cannabis use (OR=3.71, P=0.04). Daily users did not show this increase (OR=1.56, P=0.43) but instead decreased speed relative to baseline, suggesting compensatory behavior. Changes were significantly greater for occasional vs non-use groups.
Key Numbers
85 participants (31 daily, 24 occasional, 30 non-users); occasional users OR 3.71 for lane departure; daily users OR 1.56 (ns); daily users decreased speed post-use
How They Did This
Within-subjects controlled experiment with 85 adults aged 25-45: daily users (n=31), occasional users (n=24), and non-users (n=30). Participants completed driving simulator scenarios before and 30 minutes after smoking self-procured cannabis, with distraction tasks (selecting apps on a mounted tablet).
Why This Research Matters
This challenges the assumption that all cannabis users are equally impaired. Occasional users showed the greatest safety risk, while daily users compensated, suggesting tolerance and behavioral adaptation play significant roles.
The Bigger Picture
Understanding that use frequency moderates driving impairment is important for policy. A one-size-fits-all approach to cannabis-impaired driving may not reflect the actual risk landscape.
What This Study Doesn't Tell Us
Simulated driving with brief distraction tasks. Cannabis was self-procured (uncontrolled potency). Non-users did not smoke cannabis, so comparisons involve both cannabis and non-cannabis effects.
Questions This Raises
- ?Should impairment guidelines differentiate between occasional and daily cannabis users?
- ?Is the daily users' speed compensation sufficient to offset other impairment effects?
Trust & Context
- Key Stat:
- Occasional users: 3.71x lane departure risk
- Evidence Grade:
- Controlled within-subjects experiment with adequate sample size, but simulated driving and self-procured cannabis limit generalizability.
- Study Age:
- Published in 2022
- Original Title:
- Influence of cannabis use history on the impact of acute cannabis smoking on simulated driving performance during a distraction task.
- Published In:
- Traffic injury prevention, 23(sup1), S1-S7 (2022)
- Authors:
- Miller, Ryan(2), Brown, Tim(4), Wrobel, Julia(9), Kosnett, Michael J, Brooks-Russell, Ashley
- Database ID:
- RTHC-04063
Evidence Hierarchy
Watches what happens naturally without intervening.
What do these levels mean? →Frequently Asked Questions
Are occasional or daily cannabis users worse drivers after smoking?
Occasional users (1-2 times per week) were 3.7 times more likely to depart their lane during distracted driving, while daily users showed no significant increase and actually compensated by driving slower.
Why do daily users drive better after cannabis than occasional users?
The study suggests daily users develop both pharmacological tolerance and behavioral compensation strategies (like reducing speed). Occasional users lack these adaptations, making them more vulnerable to distraction-related errors.
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Cite This Study
https://rethinkthc.com/research/RTHC-04063APA
Miller, Ryan; Brown, Tim; Wrobel, Julia; Kosnett, Michael J; Brooks-Russell, Ashley. (2022). Influence of cannabis use history on the impact of acute cannabis smoking on simulated driving performance during a distraction task.. Traffic injury prevention, 23(sup1), S1-S7. https://doi.org/10.1080/15389588.2022.2072492
MLA
Miller, Ryan, et al. "Influence of cannabis use history on the impact of acute cannabis smoking on simulated driving performance during a distraction task.." Traffic injury prevention, 2022. https://doi.org/10.1080/15389588.2022.2072492
RethinkTHC
RethinkTHC Research Database. "Influence of cannabis use history on the impact of acute can..." RTHC-04063. Retrieved from https://rethinkthc.com/research/miller-2022-influence-of-cannabis-use
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.