Study: Prevalence Of Illicit Drugs In Fatal Crashes Is Low Compared To Alcohol

Study: Prevalence Of Illicit Drugs In Fatal Crashes Is Low Compared To Alcohol

Linkoping, Sweden: Alcohol is far more likely to be detected in the blood of fatally injured drivers than is the presence of either illicit substances or prescription drugs, according to data published online in the Scandanavian Journal of Public Health.

Investigators from the University of Linkoping, Department of Forensic Toxicology, evaluated the concentrations of alcohol and other drugs in blood samples from Swedish drivers killed in road-traffic crashes over a four-year period (2008-2011).

Researchers stated: "Not surprisingly, the legal drug alcohol topped the list of psychoactive substances identified in blood samples from fatally injured drivers, which confirms results and surveys done in other nations. … Indeed, in 76 percent of fatalities the autopsy BAC was over 1.0 g/L, which gives convincing evidence that these drivers were impaired at the time of the crash."

By contrast, investigators acknowledged that the presence of an illicit drug alone was only present in 2.5 percent of fatal crashes. The presence of prescription drugs was identified in nearly 8 percent of all fatal traffic accidents.

The results of the study are similar to those published in the journal Accident Analysis and Prevention in 2012, which reported that cannabis and several other illicit substances appear to be associated with only a "small or moderate increase in accident risk."

In that study, which reviewed findings from over 60 previous papers evaluating the use of illicit or prescribed drugs on accident risk, it was concluded that cannabis was associated with minor, but not dramatically increased odds of traffic injury (1.06) or fatal accident (1.25). Anti-histamines (1.12) and penicillin (1.12) were associated with comparable odds to cannabis. "Compared to the huge increase in accident risk associated with alcohol, as well as the high accident rate among young drivers, the increases in risk associated with the use of drugs are surprisingly small," the author of the study concluded.

Similarly, authors of the Swedish study reported, "Compared with alcohol, the prevalence of illicit and psychoactive prescription drugs was fairly low despite a dramatic increase in the number of drug-impaired drivers arrested by the police after a zero-tolerance law was introduced in 1999."

Under Swedish law, it is a per se traffic safety violation to operate a motor vehicle if the driver has any detectable level of an illicit drug in his or her blood. Studies assessing the imposition of Sweden’s zero tolerance per se law report that its passage has been associated with a 10-fold increase in the number of cases submitted by the police for toxicological analysis, but that the "zero-concentration limit has done nothing to reduce DUID [driving under the influence of drugs] or deter the typical offender."

A 2012 analysis of the impact of zero tolerance per se and/or per se drug laws in US states similarly found "no evidence that per se drugged driving laws reduce traffic fatalities."

Eleven US states – Arizona, Delaware, Georgia, Illinois, Indiana, Iowa, Michigan, Oklahoma, Rhode Island, Utah, and Wisconsin – impose zero tolerance per se thresholds for the presence of cannabinoids and/or their metabolites. Five states impose non-zero-tolerant per se thresholds for cannabinoids in blood: Montana (5ng/ml), Pennsylvania (1ng/ml), Ohio (2ng/ml), Nevada (2ng/ml) and Washington (5ng/ml). In Colorado, the presence of THC/blood levels above 5ng/ml "gives rise to permissible inference that the defendant was under the influence."

According to the website of the US National Highway Traffic Safety Administration (NHTSA): "It is difficult to establish a relationship between a person’s THC blood or plasma concentration and performance impairing effects. … It is inadvisable to try and predict effects based on blood THC concentrations alone."

NORML’s peer-reviewed paper critiquing the imposition of per se levels for cannabinoids is available here:

For more information, please contact Paul Armentano, NORML Deputy Director, at: Full text of the study, Prevalence of alcohol and other drugs and the concentrations in blood of drivers killed in road traffic crashes in Sweden, appears in the Scandanavian Journal of Public Health.