Earlier cannabis use onset, male sex, and living in legal states linked to more cannabis-impaired driving
Among adult cannabis users across three U.S. states, earlier age of first use, male sex, and residing in Colorado (where recreational use is legal) were associated with more frequent cannabis use, more driving after use, and more positive perceptions of driving safety after cannabis.
Quick Facts
What This Study Found
Each year of delayed cannabis onset was associated with 0.51 fewer use days/month and a lower proportion of driving-after-use days. Women used cannabis 2.3 fewer days/month and drove after use less often than men. Colorado residents reported the most use days, highest likelihood of driving within 2 hours, and most positive perceptions of safe driving after cannabis.
Key Numbers
Each year of delayed onset: -0.51 days use/month, -0.02 proportion driving-after-use days, -0.06 safety perception score. Female vs. male: -2.3 days/month, -0.06 driving proportion, -0.29 safety perception.
How They Did This
Online survey of adults aged 25-40 from Colorado (recreational legal), Illinois (medical legal at time), and Iowa (limited legal) who reported past-year cannabis use. SAS GLMSELECT procedure used for analysis.
Why This Research Matters
With cannabis legalization expanding across U.S. states, understanding which factors predict cannabis-impaired driving can help target prevention efforts to the highest-risk groups.
The Bigger Picture
The finding that living in a legal state correlates with both more use and more positive perceptions of driving safety after cannabis suggests that normalization may affect risk perception, not just access.
What This Study Doesn't Tell Us
Cross-sectional online survey with self-selected participants. Self-reported driving behavior may be underreported. Cannot determine causation. Only three states compared. Age range limited to 25-40.
Questions This Raises
- ?Does legalization cause more permissive attitudes toward impaired driving, or do states with more permissive attitudes legalize first?
- ?Would targeted public education campaigns change driving-after-use behavior?
Trust & Context
- Key Stat:
- Each year of delayed onset: 0.51 fewer use days/month
- Evidence Grade:
- Multi-state survey with statistical modeling, but cross-sectional design and self-selection limit causal claims.
- Study Age:
- Published in 2022.
- Original Title:
- A study of self-reported personal cannabis use and state legal status and associations with engagement in and perceptions of cannabis-impaired driving.
- Published In:
- Traffic injury prevention, 23(sup1), S183-S186 (2022)
- Authors:
- Brown, Timothy(7), Banz, Barbara, Schmitt, Rose(6), Gaffney, Gary, Milavetz, Gary, Camenga, Deepa, Li, Kaigang, Brooks-Russell, Ashley, Vaca, Federico
- Database ID:
- RTHC-03731
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Do people in legal states drive more after using cannabis?
In this study, Colorado residents (recreational legal) reported the most frequent cannabis use, the highest likelihood of driving within 2 hours of use, and the most positive perceptions of driving safety after cannabis, compared to Illinois and Iowa residents.
Does starting cannabis use later reduce driving risk?
Yes. Each year of delayed first cannabis use was associated with fewer use days per month, a lower proportion of days driving after use, and less positive perceptions of safe driving after cannabis.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-03731APA
Brown, Timothy; Banz, Barbara; Schmitt, Rose; Gaffney, Gary; Milavetz, Gary; Camenga, Deepa; Li, Kaigang; Brooks-Russell, Ashley; Vaca, Federico. (2022). A study of self-reported personal cannabis use and state legal status and associations with engagement in and perceptions of cannabis-impaired driving.. Traffic injury prevention, 23(sup1), S183-S186. https://doi.org/10.1080/15389588.2022.2124803
MLA
Brown, Timothy, et al. "A study of self-reported personal cannabis use and state legal status and associations with engagement in and perceptions of cannabis-impaired driving.." Traffic injury prevention, 2022. https://doi.org/10.1080/15389588.2022.2124803
RethinkTHC
RethinkTHC Research Database. "A study of self-reported personal cannabis use and state leg..." RTHC-03731. Retrieved from https://rethinkthc.com/research/brown-2022-a-study-of-selfreported
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.