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Review
. 2012;34(1):65-72.
doi: 10.1093/epirev/mxr017. Epub 2011 Oct 4.

Marijuana use and motor vehicle crashes

Mu-Chen Li  1 , Joanne E Brady, Charles J DiMaggio, Arielle R Lusardi, Keane Y Tzong, Guohua Li
Affiliations
Review

Marijuana use and motor vehicle crashes

Mu-Chen Li et al. Epidemiol Rev. 2012.

Abstract

Since 1996, 16 states and the District of Columbia in the United States have enacted legislation to decriminalize marijuana for medical use. Although marijuana is the most commonly detected nonalcohol drug in drivers, its role in crash causation remains unsettled. To assess the association between marijuana use and crash risk, the authors performed a meta-analysis of 9 epidemiologic studies published in English in the past 2 decades identified through a systematic search of bibliographic databases. Estimated odds ratios relating marijuana use to crash risk reported in these studies ranged from 0.85 to 7.16. Pooled analysis based on the random-effects model yielded a summary odds ratio of 2.66 (95% confidence interval: 2.07, 3.41). Analysis of individual studies indicated that the heightened risk of crash involvement associated with marijuana use persisted after adjustment for confounding variables and that the risk of crash involvement increased in a dose-response fashion with the concentration of 11-nor-9-carboxy-delta-9-tetrahydrocannabinol detected in the urine and the frequency of self-reported marijuana use. The results of this meta-analysis suggest that marijuana use by drivers is associated with a significantly increased risk of being involved in motor vehicle crashes.

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Figures

Figure 1.
Figure 1.
Identification, review, and selection of articles included in the meta-analysis of marijuana use and motor vehicle crashes. AMED, Allied and Complementary Medicine Database; APA Psych Info, American Psychological Association Psych Info; CINAHL, Cumulative Index to Nursing and Allied Health Literature.
Figure 2.
Figure 2.
Forest plot of study level, summary odds ratio, and 95% confidence interval (CI) of crash involvement associated with marijuana use. The size of each square is proportional to the relative weight that each study contributed to the summary odds ratio. The summary odds ratio is indicated by the diamond. Horizontal bars indicate the 95% confidence interval. Heterogeneity: Q = 38.21; P < 0.0001; I2 = 79.1.
See this image and copyright information in PMC

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