Cannabis was detected in 13% of drivers involved in traffic crashes in southern Brazil
Among 609 traffic crash victims in Porto Alegre, Brazil, 13.3% of drivers tested positive for cannabis, with alcohol abuse or dependence increasing the odds of any substance-related crash 5.2-fold.
Quick Facts
What This Study Found
Emergency room data from two Porto Alegre hospitals over 45 days identified 609 traffic crash victims. Key findings:
Drivers were mostly male (p<0.001) with higher rates of binge drinking (p=0.003) and marijuana use (p=0.005) compared to pedestrians and passengers. Cannabis prevalence was 13.3% among drivers.
Positive blood alcohol was found in 7.8% of drivers and 9.2% of pedestrians. The variables most associated with alcohol-related crashes were binge drinking in the prior year (OR 2.4) and coming from a party or bar (OR 8.7).
Alcohol abuse or dependence increased the odds of an additional substance-related crash by 5.2 times, indicating that alcohol problems substantially increased the risk of polysubstance-impaired driving.
Key Numbers
609 victims, 72% male, median age 29. Cannabis positive: 13.3% of drivers. BAC positive: 7.8% of drivers. Binge drinking: OR 2.4. Coming from party/bar: OR 8.7. Alcohol dependence increased other substance-related crash risk 5.2-fold.
How They Did This
Cross-sectional study with consecutive sampling of non-fatal traffic crash victims at two emergency rooms over 45 days. Structured interview, breathalyzer, and salivary drug testing. Multinomial logistic regression for associated factors.
Why This Research Matters
The 13.3% cannabis prevalence among crash-involved drivers in Brazil highlighted cannabis as a significant traffic safety concern beyond alcohol alone.
The Bigger Picture
This Brazilian data contributed to global evidence that cannabis-impaired driving was a significant public health issue requiring specific policy attention alongside alcohol-impaired driving.
What This Study Doesn't Tell Us
Cross-sectional emergency room sample (no comparison to non-crash drivers). Salivary testing may detect cannabis from days prior. Cannot determine whether cannabis caused or contributed to the crash.
Questions This Raises
- ?What proportion of cannabis-positive drivers were actually impaired at the time of the crash?
- ?How should Brazilian traffic safety policy address cannabis alongside alcohol?
Trust & Context
- Key Stat:
- 13.3% of crash-involved drivers tested positive for cannabis
- Evidence Grade:
- Cross-sectional emergency room study with objective drug testing but no comparison to non-crash drivers.
- Study Age:
- Published in 2011. Traffic safety research on cannabis has expanded globally.
- Original Title:
- Factors associated with alcohol and drug use among traffic crash victims in southern Brazil.
- Published In:
- Accident; analysis and prevention, 43(4), 1408-13 (2011)
- Authors:
- De Boni, Raquel, Bozzetti, Mary Clarisse, Hilgert, Juliana, Sousa, Tanara, Von Diemen, Lisia, Benzano, Daniela, Menegon, Guilherme, Holmer, Barbara, Duarte, Paulina do Carmo Arruda Vieira, Pechansky, Flavio
- Database ID:
- RTHC-00478
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
How common is cannabis-impaired driving?
In this Brazilian study, 13.3% of drivers in traffic crashes tested positive for cannabis. However, positive drug tests do not necessarily mean the driver was impaired at the time of the crash.
Is combining alcohol and drugs worse for driving safety?
This study found that having an alcohol use disorder increased the odds of a substance-related crash 5.2-fold, suggesting that alcohol problems strongly predict polysubstance impairment behind the wheel.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-00478APA
De Boni, Raquel; Bozzetti, Mary Clarisse; Hilgert, Juliana; Sousa, Tanara; Von Diemen, Lisia; Benzano, Daniela; Menegon, Guilherme; Holmer, Barbara; Duarte, Paulina do Carmo Arruda Vieira; Pechansky, Flavio. (2011). Factors associated with alcohol and drug use among traffic crash victims in southern Brazil.. Accident; analysis and prevention, 43(4), 1408-13. https://doi.org/10.1016/j.aap.2011.02.016
MLA
De Boni, Raquel, et al. "Factors associated with alcohol and drug use among traffic crash victims in southern Brazil.." Accident; analysis and prevention, 2011. https://doi.org/10.1016/j.aap.2011.02.016
RethinkTHC
RethinkTHC Research Database. "Factors associated with alcohol and drug use among traffic c..." RTHC-00478. Retrieved from https://rethinkthc.com/research/de-2011-factors-associated-with-alcohol
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.