"The estimated odds ratios of fatal motor vehicle crashes associated with different drugs reported in this population-based case-control analysis are generally consistent with previous studies (Bedard et al., 2007; Brault et al., 2004; Laumon et al., 2005; Mathijssen and Houwing, 2005; Movig et al., 2004; Mura et al., 2003). For instance, in a case-control study conducted in the Netherlands, Movig et al. (2004) found that 11.8% of the drivers who were seriously injured in crashes and 6.0% of the drivers who were not involved in crashes tested positive for marijuana, yielding an odds ratio of 2.1 (95% CI: 1.1, 4.0). A study of drivers aged 18 to 69 years of age in Norway revealed that the incidence of crashes was more than two times higher for individuals the week after benzodiazepine-like hypnotics were dispensed compared to unexposed person time (Gustavsen et al., 2008). A meta-analysis of epidemiological studies showed that motor vehicle crash risk for benzodiazepine users was 60–80% higher than for nonusers (Dassanayake et al., 2011). It is also evident that crash risk in drivers with depression is particularly high at the initiation of antidepressant treatment and when antidepressant treatment regimen changes (Orriols et al., 2012)."

Source

Guohua Li, Joanne E. Brady, and Qixuan Chen. Drug use and fatal motor vehicle crashes: A case-control study. Accident Analysis and Prevention 60 (2013) 205–210. http://dx.doi.org/10.1016/j.a….
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