A potential unintended consequence of legalizing recreational marijuana is increased marijuana-related driving impairment. Some states where recreational marijuana is legal have begun implementing interventions to mitigate driving under the influence (DUI) of marijuana, including media campaigns to increase knowledge about DUI laws. However, little is known about the associations between knowledge of DUI laws and marijuana DUI behavior. In this study, we provide new data from a survey of marijuana users in Colorado and Washington to examine associations between marijuana drugged driving and two potential behavioral precursors of marijuana DUI. We also explore other factors that may influence marijuana DUI.
Data are from an online survey of marijuana users in Colorado and Washington. Respondents who reported any marijuana use in the past 30 days (n = 865) served as the analytic sample. We examined prevalence of two behavioral outcomes: (1) any driving of a motor vehicle while high in the past year and (2) driving a motor vehicle within 1 hour of using marijuana 5 or more times in the past month. Additional outcomes measuring willingness to drive while high were also assessed. Logistic regressions were used to estimate each outcome as a function of two multi-item scales measuring knowledge of the legal consequences of driving high and perceptions that driving while high is not safe. Additional covariates for potential confounders were included in each model.
Prevalence of past-year driving while under the influence of marijuana was 43.6% among respondents. The prevalence of driving within 1 hour of using marijuana at least 5 times in the past month was 23.9%. Increased perception that driving high is unsafe was associated with lower odds of past-year marijuana DUI (OR = 0.31, P < 0.01) and lower past-month odds of driving 5 or more times within 1 hour of using marijuana (OR = 0.26, P < 0.01). Increased knowledge of marijuana DUI laws was also associated with lower odds of each of these outcomes (OR = 0.63, P < 0.01, OR = 0.69, P = 0.02, respectively). Post-estimation Wald tests confirmed the negative associations with marijuana DUI were greater in magnitude for safety perceptions than knowledge of DUI laws. Increased perceptions that driving while high is unsafe was associated with significantly lower willingness to drive after using marijuana while increased knowledge of marijuana DUI laws was not associated with these outcomes.
Despite recent interventions targeting public awareness of the legal consequences of marijuana DUI, our results suggest that knowledge of these laws is a weaker predictor of DUI behavior than perceptions that driving high is unsafe. In addition, safety perceptions predict decreased openness to driving high while knowledge of DUI laws was not associated with openness. These findings suggest that interventions for reducing the incidence of marijuana DUI are likely to be more successful by targeting safety perceptions related to marijuana DUI rather than knowledge of DUI laws. We caution that because these data are limited to an online convenience sample, results may not be generalizable beyond our sample.
|Sample Characteristic||Proportion (n = 865)|
|18 to 24||8.7%|
|25 to 34||21.2%|
|35 to 54||38.4%|
|55 or older||31.8%|
|Did not graduate high school||1.6%|
|High school or GED||13.6%|
|Some college, no degree||29.4%|
|College degree or higher||55.4%|
|Behavior and Openness Outcome||Past 30-daymarijuana users(n = 865)|
|Percentage of marijuana users who report driving a car or other motor vehicle while high or feeling the effect of marijuana or hashish in past year||43.6% [40.3–47.0]|
|Percentage of marijuana users who report 5 or more times in the past 30 days driving a motor vehicle within 1 hour of consuming marijuana or hashish||23.9% [20.3–27.6]|
|Percentage of marijuana users who agree or strongly agree that “I might drive high even though I know I shouldn’t.”||52.7% [49.3–56.1]|
|Percentage of marijuana users who agree or strongly agree that “In certain situations, I might drive high.”||41.3% [37.9–44.6]|
Full article at: http://goo.gl/1xbERp
By: Kevin C. Davis,* Jane Allen, Jennifer Duke, James Nonnemaker, Brian Bradfield, Matthew C. Farrelly, Paul Shafer, andScott Novak
Giuseppe Remuzzi, Editor
RTI International, Research Triangle Park, NC, United States of America
Mario Negri Institute for Pharmacological Research and Azienda Ospedaliera Ospedali Riuniti di Bergamo, ITALY
Competing Interests: The authors have declared that no competing interests exist.
Analyzed the data: BB PS. Wrote the paper: KCD JA JD JN BB MCF PS SN.
* E-mail: gro.itr@sivadck
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