Cannabis, alcohol and fatal road accidents . An increased risk linked to opiate use has also been found to be significant, but with low. Most cannabis use is intermittent and Risk factors for having a fatal. But then pro-legalization advocates retort that alcohol is also legal and causes many more traffic accidents than marijuana, and that's
and increases THC fatal alcohol accidents of risk
They are thus considered too sensitive to be publicly available. Following the consortium agreement, data are available upon request to interested researchers, provided that they specify the objectives pursued and that the consortium agrees to make data available. To apply for data access, interested researchers may contact Jean-Louis Martin rf.
This research aims to estimate the relative risks of responsibility for a fatal accident linked to driving under the influence of cannabis or alcohol, the prevalence of these influences among drivers and the corresponding attributable risk ratios. A secondary goal is to estimate the same items for three other groups of illicit drugs amphetamines, cocaine and opiates , and to compare the results to a similar study carried out in France between and Police procedures for fatal accidents in Metropolitan France during were analyzed and characteristics encoded to provide a database of 4, drivers.
Information on alcohol and four groups of illicit drugs derived from tests for positivity and potential confirmation through blood analysis. The study compares drivers responsible for causing the accident, that is to say having directly contributed to its occurrence, to drivers involved in an accident for which they were not responsible, and who can be assimilated to drivers in general.
The proportion of persons driving under the influence of alcohol is estimated at 2. Drivers under the influence of alcohol are Drivers under the influence of cannabis multiply their risk of being responsible for causing a fatal accident by 1. An increased risk linked to opiate use has also been found to be significant, but with low prevalence, requiring caution in interpreting this finding. Other groups of narcotics have even lower prevalence, and the associated extra risks cannot be assessed.
Almost a decade separates the present study from a similar one previously conducted in France, and there have been numerous developments in the intervening years. Even so, the prevalence of drivers responsible for causing fatal accidents under the influence of alcohol or narcotics has stayed remarkably stable, as have the proportion of fatal accidents which could in theory be prevented if no drivers ever exceeded the legal limits. Alcohol remains the main problem in France.
It is just as important to note that one in two drivers considered to be under the influence of cannabis was also under the influence of alcohol. With risks cumulating between the two, it is particularly important to point out the danger of consuming them together.
Ever since the Grand Rapids study [ 1 ], all published research, whether experimental or observational, has shown a higher accident risk for drivers under the influence of alcohol [ 2 — 5 ].
This strongly increased risk can chiefly be explained by greatly reduced attentional and cognitive capacities, a delay in taking actions that could avoid an accident, and a higher degree of risk-taking [ 6 ], in particular, driving at high speed. In recent years, there have also been numerous studies into driving under the influence of illicit drugs, notably cannabis. A number of experimental investigations have shown a decreased capacity of drivers under the influence of cannabis [ 7 — 9 ], in particular a decrease in attention, increased reaction time and reduced ability to control direction [ 10 ].
Individual variations are considerable, but there is an overall diminution in cognitive and motor functions related to driving. A further dose-dependent effect has been demonstrated in certain aspects of vehicle control, such as steering, keeping distance from the vehicle ahead, driving speed, reaction time and keeping on the right side of the road [ 11 ].
These experimental studies are indispensable for knowing how consumption of a given substance affects driving, and the intensity of its effect.
On the other hand, for obvious ethical reasons, the doses to which the consumers are experimentally subjected are limited to reasonable levels, which in real life are often widely exceeded, for illegal drugs as well as alcohol. Moreover, in spite of constant technical progress in driving simulators, it is difficult for drivers to forget they are not on a real road, and that an error would not pose a danger as it would in real-life conditions.
Driving on a test track is closer to reality, but still does not completely avoid the same criticism, given that courses are pre-established and drivers know they are being supervised. Finally, under controlled conditions, it is not certain that drivers adapt to their perceived capacities in the same way as in a real-life driving situation. For all of these reasons, real-life observation studies are essential.
Furthermore, they can estimate the prevalence of driving under the influence of alcohol or illegal drugs. Hitherto published research essentially falls into two categories: In a recent study, Hartman differentiated the design of epidemiological studies in a review of the literature [ 12 ].
Ten case-control studies were examined, in which the control subjects were drivers not involved in any accident. Six of these case-control studies relied on self-report to determine use of cannabis. According to the authors, this would tend to minimize the odds ratio associated with driving under the influence when it comes to use of an illegal substance.
For all of these case-control studies, the reliability of the results depends on the comparability of cases and controls. Studies based on determining responsibility, and assessing the increased risk of being responsible for an accident while under the influence, have the advantage of directly measuring the substances consumed in the two groups.
They involve, however, an estimate of responsibility that requires knowledge of numerous elements of the circumstances of the accident.
This was the method selected for the present study. Three recent reviews [ 13 — 15 ] in particular confirmed the order of magnitude of increased risk associated with driving under the influence of cannabis, estimated in France at 1. The odds ratio OR connected to cannabis is estimated at 1. Another review of the literature [ 13 ] recalculated the crude risks for road users who had not consumed alcohol, so as to isolate the effect of cannabis in all the studies, which were selected according to quality standards specified in the article.
In this way, the OR was re-estimated at 1. Finally, the review by Li [ 14 ] estimated the crude OR at 2. Five of the nine studies used self-reporting to estimate cannabis consumption.
The advantage of estimates derived from meta-analyses lies in their quantitative synthesis of numerous and sometimes contradictory results. One of the issues is however that the results are often weighted from crude relative measures, or from measures adjusted for very different factors. In particular, it appears difficult for the risk linked to cannabis use not to take into account the consumption of alcohol with which it is often associated [ 17 ].
In France during —, almost half of drivers involved in fatal crashes and found to be under the influence of cannabis were also under the influence of alcohol. As alcohol is associated with a higher OR, the risk associated with cannabis in the presence of alcohol is multiplied by this OR even in the absence of any positive interaction. It has further been shown in experimental conditions that drivers under the influence of alcohol tend to drive faster [ 18 ], which goes hand in hand with an overestimation of their own capacities [ 10 ], whereas drivers under the influence of cannabis tend to drive more cautiously [ 19 , 20 ].
Therefore, priority should be given to studies on the influence of using cannabis while driving that concomitantly assess the influence of alcohol. The main objective of this research was to estimate the relative risks of responsibility for a fatal accident linked to driving under the influence of cannabis or alcohol, the prevalence of these influences when driving, and the attributable risk fractions to which they correspond.
Two secondary objectives were to estimate the same items for three other families of illegal narcotics amphetamines. As the need arose, data collection services provided important elements that were missing, such as accident diagrams, photographs of the vehicles involved, and injury assessments. The collected data concerned all fatal accidents with at least one people dead on the spot or within the 30 days following the road accident occurring in Metropolitan France in the year The database therefore included 3, accidents described through more than variables.
Also encoded were the configuration and situation of accidents, human dysfunction, maneuvers of road users prior to the accident, collisions during the accident as well as any conflicts identified as playing a role in the occurrence of the accident. Conversely, information about driver health status was rarely reported by the police, nor possible confounding factors such as cell phone use or other driver distraction factors. With regard to narcotics, information was available on cannabis, opiates, amphetamines and cocaine.
The method of data collection was indicated, and the drug concentration was measured, when possible, for all drivers killed as well as survivors found positive on detection tests.
Fig 1 shows the numbers of drivers under influence or not or unknown status for alcohol and THC. The process is described separately for drivers killed within 30 days after the crash or alive in the same period, as the screening was most of the time impossible for the formers. Numbers of drivers with known alcohol and drug are indicated in parenthesis. The final work sample includes drivers. Numbers of drivers assessed positive, negative or with unknown status for alcohol and THC.
Estimating the degree of intoxication for cannabis and other narcotics is a trickier task than for alcohol. As far as cannabis is concerned, the effects vary rapidly with time. There is a rapid rise in the first fifteen minutes after consumption, followed by a fairly rapid decline [ 7 ]. The variety of substances and their means of consumption can also pose problems of measurement. However, the active ingredient behind most of the effects of cannabis that impair driving ability is THC.
Metabolites such as THC-COOH are present and detectable for a significant time after consumption, but lack any proven psychoactive effects capable of impairing driving ability [ 21 ]. Cannabis intake is initially assessed either by urine or saliva test; confirmation and blood concentration are obtained through blood sampling.
Only the result of the blood sample is deemed proof of positivity. In order to determine the narcotic status of the driver, the following rule is therefore applied:. The minimum regulatory for detection thresholds in urinary and salivary tests for the different families of narcotics are as follows:. Any driver whose blood tests above or equal to the prescribed level for one or other of the classified narcotic substances is deemed positive for narcotics. Blood positivity levels are shown in the results tables.
For cannabis, THC is screened. To determine alcohol status, the driver must first submit to an alcohol screening test. The responsibility of a road user is not defined here in a legal sense. Rather, a person who contributes to or causes an accident is considered responsible, perhaps by an inappropriate maneuver wrong-way driving, ignoring a traffic light, evident loss of control, etc.
Otherwise, the effects of these factors on the risk of responsibility would be greatly overestimated. Responsibility was determined by a team of experts, drawing on all the facts at their disposal, including plans of the accident, and the comments of those involved and of the police.
Responsibility was ranked in 5 categories: The responsible group included drivers whose responsibility was ranked 1, 2 or 3. Put another way, the accident would not have taken place if one or other of the drivers had not done something that leads an expert to assign them all or part of the responsibility.
With this approach, it is possible to have several responsible parties to the same accident. The group of non-responsible parties includes drivers whose responsibility was ranked 4 or 5. These drivers are deemed fortuitously involved in the accident, through the misfortune of being in the wrong place at the wrong time. From the concept of responsibility, this study may be considered from an epidemiological standpoint as a case-control study.
The source population comprised all drivers who use public roads or private roads open to public traffic, and the two groups were drawn from this population since they had been involved in an accident that satisfied this inclusion criterion.
Factors positively linked to responsibility can be interpreted as factors facilitating occurrence of the accident [ 24 , 25 ], on condition that they satisfy certain criteria, besides significant statistical association [ 26 ]. In practice, the significance of a risk factor for an accident fatal or physical injuries is gauged, as for a classic case-control study, by an odds ratio OR and an attributable risk AR.
The OR is a good approximation of the corresponding relative risk RR , provided that the control group can be considered as representative of drivers. More precisely, we apply a model logistic regression to estimate the effect of each variable, either by itself crude OR or adjusted to fit the other variables retained in the model adjusted OR. An OR is deemed significantly different to 1 if its confidence interval does not include the value 1.
The calculations are made using SAS software, version 9. The prevalence among the population of driving under the influence of alcohol and cannabis is estimated from the control population always assuming that drivers have a very weak probability of having an accident when traveling. By definition, it is the proportion of accidents that would be avoided in the hypothetical complete absence of considered exposure E driving under the influence of alcohol or drugs:.
Strictly speaking, the interpretation of this attributable risk depends on two hypotheses:. In the absence of overlooked confounding variables, an AR formula [ 27 , 28 ] allows us to consider at the same time the approximation of RR by OR, multi-level exposure, the adjustment on confounding factors, and possible interaction between these factors:.
An analysis was made of 2, accidents out of 3, fatal accidents occurring in Metropolitan France in and of the corresponding 4, drivers tested for alcohol and narcotics, and of expert-determined responsibility. Among the included drivers, there was a slightly higher proportion of males and young people than in the total population of drivers involved in fatal accidents.
Factors influencing inclusion did not significantly differ between responsible and non-responsible parties. As indicated in the Materials and Methods section, the risk of being responsible for causing a fatal accident for a driver under compared to a driver not under the influence was estimated by comparing ORs between responsible cases and non-responsible drivers controls.
Table 1 shows estimated crude ORs according to detected substance. With these crude ORs, it appears that the risk of being responsible for causing a fatal accident is much increased for drivers under the influence of alcohol x It is multiplied by 3.
The risks associated with drivers under the influence of amphetamines or cocaine are increased but are not significantly different from 1: For cannabis and alcohol, it is possible to provide detailed results by measured dose Table 2. As expected, the risk increases with the measured amount of alcohol. Table 3 shows the prevalence of cannabis and alcohol according to adjustment factors to be introduced in the model.
The prevalences of cannabis and alcohol appear lower for women. The prevalence of cannabis was clearly lower for those aged 35 and above, which was not observed for alcohol. As far as the user categories are concerned, moped riders had the strongest prevalence of cannabis and alcohol, followed by motorcyclists. Finally, prevalence was clearly greater at night, and greater still at night during weekends. Table 4 details the ORs for factors of interest according to measured dose, adjusted for the four preceding factors.
The effects of cannabis, alcohol and opiates remained significant after adjusting for all of the co-factors likely to have an influence on responsibility. All first-order 1 interactions were tested. Table 5 shows estimated attributable risks calculated from the above adjusted estimates. The risk fraction attributable to driving under the influence of alcohol appears very high, How Do Drug Overdoses Happen? State and Federal Drug Laws. Red Ribbon Week Oct. National Take Back Day is April Upcoming DEA Events.
WAFB , July 12 We are all aware of the dangers of drinking alcohol and driving, but marijuana use before driving also increases your risk of being involved in a deadly car accident, according to a new study. Researchers from the Columbia University Mailman School of Public Health looked at more than 14, drivers who were at fault in accidents, and the same number of drivers who were not at fault for the crash.
They found that 28 percent of at-fault motorists tested positive for alcohol, 10 percent tested positive for marijuana, and four percent had both in their systems. Also, according to the numbers: People who tested positive for both alcohol and marijuana were six times more likely to die in an accident; testing positive for marijuana makes someone 62 percent more likely to be responsible for a car crash.
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Cannabis, alcohol and fatal road accidents
People commonly combine marijuana and alcohol, and as marijuana An overdose on alcohol is very serious and can obviously be fatal. or engage in behaviors that can lead to accidents and serious consequences. of drug abuse of any type include increased risk to develop cardiovascular issues. While decades of research have shown that alcohol increases the risk of vehicle crashes, marijuana research is mixed. Still, it's clear enough. Combining marijuana with alcohol raises your risk of causing a fatal car within the past few hours can increase your risk of causing a crash.