Cannabis use and self-reported collisions in a representative sample of adult drivers

ArticleinJournal of Safety Research 38(6):669-74 · February 2007with12 Reads
DOI: 10.1016/j.jsr.2007.09.004 · Source: PubMed
This study examines the relationships between collision involvement and several measures of cannabis use, including driving after using cannabis, among drivers, based on a population survey of Ontario adults in 2002 and 2003. Logistic regression analyses examined self-reported collision involvement in the last 12 months by lifetime use of cannabis, past year use of cannabis, and past year driving after using cannabis, while controlling for demographic characteristics. We found that the odds of reporting collision involvement was significantly higher among cannabis users, and among those who reported driving after cannabis use. Some evidence for a dose-response relationship was seen as well. Cannabis users and people who report driving after cannabis use are also more likely to report being involved in a collision in the past year. These observations suggest that collision prevention efforts could be aimed at these groups. Additional work to determine the causal pathways involved in the relationships observed here is needed. None.
    • "However, the effect of cannabis on driving performance is less well established. Research generally shows that recent cannabis use impairs some measures of simulated and on-road driving performance151617181920 and increases the risk of crash involvement [11,21222324 in a doserelated manner [15,25] but others found no statistically significant effect2526272829303132. One potential reason for this discrepancy may be that drivers impaired by cannabis are often aware of their impairment and employ behavioral strategies to compensate, such as driving more slowly and increasing their following distance14151620]. "
    [Show abstract] [Hide abstract] ABSTRACT: Background/objectives: Driving under the influence of alcohol or cannabis alone is associated with increased crash risk. This study explores the combined influence of low levels of alcohol (BAC≤0.08) and cannabis on crash risk. Materials and methods: Drivers aged 20 years or older who had been tested for both drugs and alcohol after involvement in a fatal crash in the United States (1991-2008) were examined using a case-control design. Cases were drivers with at least one potentially unsafe driving action (UDA) recorded in relation to the crash (e.g., weaving); controls had none recorded. We examined the prevalence of driving under the influence of alcohol, cannabis, and both agents, for drivers involved in a fatal crash. Adjusted odds ratios of committing an UDA for alcohol alone, THC alone, and their combined effect were computed via logistic regression and adjusted for a number of potential confounders. Results: Over the past two decades, the prevalence of THC and alcohol in car drivers involved in a fatal crash has increased approximately five-fold from below 2% in 1991 to above 10% in 2008. Each 0.01 BAC unit increased the odds of an UDA by approximately 9-11%. Drivers who were positive for THC alone had 16% increased odds of an UDA. When alcohol and THC were combined the odds of an UDA increased by approximately 8-10% for each 0.01 BAC unit increase over alcohol or THC alone. Conclusion: Drivers positive for both agents had greater odds of making an error than drivers positive for either alcohol or cannabis only. Further research is needed to better examine the interaction between cannabis concentration levels, alcohol, and driving. This research would support enforcement agencies and public health educators by highlighting the combined effect of cannabis at low BAC levels.
    Article · Dec 2014
    • "While the importance of the role of economic evaluations in such a systematic assessment has been recognised, to date there has been no quantification of the significant costs and benefits of one legal option over the status quo. Past research has examined selected outcomes of a policy change; for example, the cost impacts on the criminal justice system [9], [16], [17], [18]; gains in taxation income [9], [16]; impacts on use [16], [19], [20]; on educational attainment [21], [22], [23]; and on driving [24], [25]. However, to our knowledge no previous research has combined and valued the wide range of costs and benefits of cannabis policies, nor included individuals’ costs and benefits. "
    [Show abstract] [Hide abstract] ABSTRACT: To date there has been limited analysis of the economic costs and benefits associated with cannabis legalisation. This study redresses this gap. A cost benefit analysis of two cannabis policy options the status quo (where cannabis use is illegal) and a legalised-regulated option was conducted. A cost benefit analysis was used to value the costs and benefits of the two policies in monetary terms. Costs and benefits of each policy option were classified into five categories (direct intervention costs, costs or cost savings to other agencies, benefits or lost benefits to the individual or the family, other impacts on third parties, and adverse or spill over events). The results are expressed as a net social benefit (NSB). The mean NSB per annum from Monte Carlo simulations (with the 5 and 95 percentiles) for the status quo was $294.6 million AUD ($201.1 to $392.7 million) not substantially different from the $234.2 million AUD ($136.4 to $331.1 million) for the legalised-regulated model which excludes government revenue as a benefit. When government revenue is included, the NSB for legalised-regulated is higher than for status quo. Sensitivity analyses demonstrate the significant impact of educational attainment and wellbeing as drivers for the NSB result. Examining the percentiles around the two policy options, there appears to be no difference between the NSB for these two policy options. Economic analyses are essential for good public policy, providing information about the extent to which one policy is substantially economically favourable over another. In cannabis policy, for these two options this does not appear to be the case.
    Full-text · Article · Apr 2014
    • "Examining cannabis consumption rather than DUIC has generally produced nonsignificant or lower odds ratios (ORs) than targeting DUIC. More frequent cannabis exposure (addiction patients; more than once a week, 4 days/week) was associated with a significantly increased MVA risk (risk ratio, 1.49; OR, 2.76 and 2.5, respectively) (27, 30, 31 ). A crude 11.4 OR for MVA injury within 3 h of cannabis smoking dropped to a nonsignificant OR of 0.8 after adjusting for confounders (28 ), whereas DUIC after smoking during the previous hour almost doubled crash risk [ORs, 1.84 (21 ) and 2.61 (27 )], a finding that withstood adjustment for demographic characteristics (21, 27 ) and self-reported driving under the influence of alcohol (21 ). "
    [Show abstract] [Hide abstract] ABSTRACT: Background: Cannabis is the most prevalent illicit drug identified in impaired drivers. The effects of cannabis on driving continue to be debated, making prosecution and legislation difficult. Historically, delays in sample collection, evaluating the inactive Δ(9)-tetrahydrocannabinol (THC) metabolite 11-nor-9-carboxy-THC, and polydrug use have complicated epidemiologic evaluations of driver impairment after cannabis use. Content: We review and evaluate the current literature on cannabis' effects on driving, highlighting the epidemiologic and experimental data. Epidemiologic data show that the risk of involvement in a motor vehicle accident (MVA) increases approximately 2-fold after cannabis smoking. The adjusted risk of driver culpability also increases substantially, particularly with increased blood THC concentrations. Studies that have used urine as the biological matrix have not shown an association between cannabis and crash risk. Experimental data show that drivers attempt to compensate by driving more slowly after smoking cannabis, but control deteriorates with increasing task complexity. Cannabis smoking increases lane weaving and impaired cognitive function. Critical-tracking tests, reaction times, divided-attention tasks, and lane-position variability all show cannabis-induced impairment. Despite purported tolerance in frequent smokers, complex tasks still show impairment. Combining cannabis with alcohol enhances impairment, especially lane weaving. Summary: Differences in study designs frequently account for inconsistencies in results between studies. Participant-selection bias and confounding factors attenuate ostensible cannabis effects, but the association with MVA often retains significance. Evidence suggests recent smoking and/or blood THC concentrations 2-5 ng/mL are associated with substantial driving impairment, particularly in occasional smokers. Future cannabis-and-driving research should emphasize challenging tasks, such as divided attention, and include occasional and chronic daily cannabis smokers.
    Full-text · Article · Dec 2012
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