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Drugs: Their Use is Tied to Fatal Car Crashes


A new study, reported in the July issue of the Journal of Studies on Alcohol and Drugs, suggests that alcohol is not the only drug that can result in fatal car crashes.

While common sense would suggest drugs like marijuana or amphetamines would impair drivers and lead to crashes, few studies have actually looked specifically at the impact of other drugs on traffic deaths.

In the United States, the 2007 National Roadside Survey found that the percentage of drivers who were using drugs (14%) was greater than the percentage who were using alcohol (12%). This led the White House Office of National Drug Control Policy (2010) to call for states to pass drug per se laws in 2010. Currently, 17 U.S. states have drugged-driving per se laws, of which 15 specify zero tolerance for any measureable amount of an illicit drug.

Eduardo Romano, Ph.D. and Robert B. Voas, Ph.D., of the Pacific Institute for Research and Evaluation in Calverton, Maryland, analyzed data from the Fatality Analysis Reporting System (FARS), which is a census of all crashes on U.S. public roads that result in a death within 30 days.

FARS contains an estimate of the blood alcohol concentration (BAC) of every driver involved in a fatal crash based on an actual measurement, but drug information is more limited. Only 20 of the 50 states have provided drug use information on at least 80% of their fatally injured drivers.

Romano and Voas found that of U.S. drivers who died in a crash, about 25% tested positive for drugs. The most common drugs were marijuana and stimulants, including cocaine and amphetamines, which each accounted for almost one quarter of the positive tests.

It’s not clear whether the drugs were to blame for the crashes, the researchers say. Some people who use illegal drugs may simply be reckless drivers in general, for instance.

On the other hand, a recent government study found that of U.S. drivers who were randomly pulled over, 14% tested positive for drugs. The fact that drug use was almost twice as high among drivers in fatal crashes suggests that drugs do contribute to road deaths.

“The suspicion is there, because when you look at drivers who’ve been in fatal crashes, the percentage using drugs is a good deal higher,” said study co-author Robert B. Voas, Ph.D., of the Pacific Institute for Research and Evaluation in Calverton, Maryland.

For the general public, the message is simple.

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“Don’t drink or don’t consume drugs when you’re going to drive,” said Eduardo Romano, Ph.D., the lead author on the study.

Between 1998 and 2009, there were more than 44,000 fatally injured drivers with drug-test information—one quarter of whom tested positive for drugs. Marijuana and stimulant drugs including cocaine and methamphetamine were the most commonly implicated.

It turned it out that stimulants were linked to all types of crash fatalities—whether from speeding, failure to obey other traffic laws, inattention, or forgoing seatbelts. Marijuana, on the other hand, was tied only to speeding and seatbelt non-use. That lays out the possibility that stimulants are particularly impairing, but that’s not yet clear, the researchers say.

Whatever the effects of different drugs, alcohol still appears to be the biggest roadway hazard.

This study found that, in general, other drugs seemed to be key only when drivers had not been drinking as well. That is, when someone drinks and does drugs, the alcohol is the main reason for impaired driving.

“Alcohol is still the largest contributor to fatal crashes,” Romano said.

It is important, Romano and Voas say, for researchers to keep studying how various drugs might impair drivers.

The above story is relies on materials provided by Pacific Institute for Research and Evaluation (with editorial adaptations by Ramona Bates, MD)

Drug and Alcohol Involvement in Four Types of Fatal Crashes; Romano, E, & Voas, R. B.; Journal of Studies on Alcohol and Drugs, July 2011, available online as of June 23, 2011

Centers for Disease Control and Prevention: Impaired Driving

Stop Drugged Driving