Among 17,405 cannabis users, men who used both medically and recreationally had a 40% probability of driving under the influence of cannabis, compared to 20% for women using medically only.
Traffic safety researchers, public health officials, and cannabis policy makers.
40% DUIC probability among male combined medical/recreational users
What the researchers found
Male cannabis users who combined medical and recreational use had the highest probability of DUIC (40%), while female medical-only users had the lowest (20%). Women showed similar DUIC rates regardless of use reason (20-25%), while men varied widely (28-40%). The sex difference was most pronounced among combined medical/recreational users.
Why it matters
As both medical and recreational cannabis expand, understanding who is most likely to drive impaired helps target prevention. Men who use for both purposes emerge as the highest-risk group.
The numbers in context
17,405 cannabis users; 88.1% recreational, 7.8% medical, 4.1% both; DUIC probability: male combined users 40%, female medical-only 20%.
How the study worked
Cross-sectional analysis of 17,405 past-year cannabis users (18+) from the 2016-17 National Survey on Drug Use and Health, using multivariable logistic regression with sex-by-reason interaction.
What this study cannot tell us
Cross-sectional survey with self-reported DUIC; cannot establish that DUIC was actually impaired driving; does not assess actual impairment or crash risk; reasons for use may overlap with other risk factors.
How to read the evidence
Moderate: large nationally representative sample with appropriate statistical methods, but cross-sectional with self-reported outcomes.
When this study was published
Published 2020.
The bigger picture
The finding that medical cannabis users drive impaired at meaningful rates challenges the assumption that medical use is inherently more responsible. Combining medical and recreational use patterns appears to create the highest risk.
Questions still open
- Why do men show more variation in DUIC by reason for use than women? Would targeted interventions for dual-purpose male users reduce cannabis-impaired driving?
Common questions
Who is most likely to drive high?
Do medical cannabis patients drive impaired?
Read the original research
Sex differences in driving under the influence of cannabis: The role of medical and recreational cannabis use.
Addictive behaviors, 110, 106525
Citation
Lloyd, Shawnta L; Lopez-Quintero, Catalina; Striley, Catherine W. (2020). Sex differences in driving under the influence of cannabis: The role of medical and recreational cannabis use.. Addictive behaviors, 110, 106525. https://doi.org/10.1016/j.addbeh.2020.106525