Nearly a third of drivers in fatal car crashes have drugs in system

Nearly one-third of drivers involved in fatal car accidents are found to have at least one non-alcohol drug in their system, and those with such drugs in their system are three times more likely to be involved in a fatal crash than those without, according to a new study.

Driving under the influence of drugs – "drugged driving" – has long been seen as a problem for public health officials in the U.S., but according to the authors of the new study, conducted by Columbia University's Mailman School of Public Health, the negative impact of drugs in fatal car crashes is a more urgent public health issue than scant existing literature previously indicated.

The findings also looked at the impact that drugs and alcohol have when used in tandem, showing that drivers who take them together have an even greater likelihood of being in a fatal crash than if they are under the influence of one or the other.

While heightened alcohol levels were found in more than 50 percent of fatal crashes, more than 20 percent involved a driver with alcohol and at least one drug in the system.

Compared to someone who had neither drugs nor alcohol in their system, drivers with alcohol were only 13 times more likely to be involved in a fatal crash, while those with both alcohol and drugs in their system were 23 times more likely.

"The possible interaction of drugs in combination with alcohol on driving safety has long been a concern," said Dr. Guohua Li, one of the study's authors, in a press release on the Columbia website.

"While alcohol-impaired driving remains the greatest threat to traffic safety, these findings about drugged driving are particularly salient in light of the increases in the availability of prescription stimulants and opioids over the past decade," she said.

Despite the findings, the authors of the study nonetheless admitted the difficulty of assessing the impact of various drugs on a person's ability to operate a vehicle. For one, the study includes people with drugs in their systems, but not necessarily a person that was proven to be impaired by said drug.

Part of the difficulty in determining drug impairment, moreover, is a result of pharmacological differences between various drugs and the varied tolerances that individuals have to them. Unlike alcohol, which is easy to measure in real time through levels in the blood, no uniform measures exists to determine drug impairment, the study's authors said.

Among the drugs looked at by the study, depressants were found to be the leading culprit in drug-related crashes, followed by stimulants, narcotics and finally marijuana.

Data for the findings was provided by two separate national databases compiled by the National Highway Traffic Safety Administration.

The study findings are published in the journal, Accident Analysis and Prevention.