Background Cannabis use has been linked to impaired driving and fatal accidents. Prior evidence suggests the potential for population-wide effects of the annual cannabis celebration on April 20th (‘4/20’), but evidence to date is limited.
Methods We used data from the Fatal Analysis Reporting System for the years 1975–2016 to estimate the impact of ‘4/20’ on drivers involved in fatal traffic crashes occurring between 16:20 and 23:59 hours in the USA. We compared the effects of 4/20 with those for other major holidays, and evaluated whether the impact of ‘4/20’ had changed in recent years.
Results Between 1992 and 2016, ‘4/20’ was associated with an increase in the number of drivers involved in fatal crashes (IRR 1.12, 95% CI 0.97 to 1.28) relative to control days 1 week before and after, but not when compared with control days 1 and 2 weeks before and after (IRR 1.05, 95% CI 0.92 to 1.28) or all other days of the year (IRR 0.98, 95% CI 0.88 to 1.10). Across all years we found little evidence to distinguish excess drivers involved in fatal crashes on 4/20 from routine daily variations.
Conclusions There is little evidence to suggest population-wide effects of the annual cannabis holiday on the number of drivers involved in fatal traffic crashes.
- public health
- descriptive epidemiology
- Motor vehicle Occupant
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Contributors SH and AP conceptualised and designed the study. SH acquired the data and conducted the analysis. SH and AP interpreted the findings and wrote the paper. Both authors read and approved the final version of the manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval This study used publicly available data and did not require ethics review.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The data and code to replicate our findings are posted in a public repository (https://osf.io/qnrg6/).