Driving After Marijuana Use

July 10, 2014

By Eric Sarlin, M.Ed., M.A.,
NIDA Notes Contributing Writer
National Institute on Drug Abuse
The Science of Drug Abuse & Addiction

Nearly 1 in 6 high school seniors who responded to a 2011 survey reported that, within the past 2 weeks, they had driven a motor vehicle after using an illicit drug or drinking heavily. Nearly 1 in 4 said they had recently ridden in a car with such a driver. Altogether 28% had put themselves at risk, within that short time frame, by being in a vehicle whose driver had been using marijuana or another illicit drug, or had consumed 5 or more alcoholic drinks. These rates had all risen nearly 20% in only 4 years, due almost entirely to an increase in driving after smoking marijuana.

The students’ responses also disclosed that, among 12th graders, driving after marijuana use has become more common than drinking and driving. About 1 in 8 (12.4%) reported that within the past 2 weeks they had driven after using marijuana, whereas 1 in 11 (8.7%) had driven after drinking alcohol. The prevalence of high school seniors driving after using marijuana had risen sharply from 10.4% in the 2008 iteration of the survey, while that of drinking and driving had declined from a peak of 16% in 2002. These changes parallel overall trends in students’ use of marijuana and alcohol.

Alcohol’s detrimental effects on road safety are well known, but it has been less clear whether marijuana produces similarly dangerous effects. Although the survey did not capture whether the teens were under the influence of alcohol or marijuana at the of any traffic incidents they reported being involved in, two of its findings underscore that marijuana use is associated with key indicators of dangerous driving. The high school seniors who drove after marijuana use and after heavy drinking were similarly likely to have had accidents (26.9% and 30.2%, respectively) and to have received traffic tickets or warnings (42.1% and 43.2 %, respectively) during the 12 months prior to taking the survey. The rates for these misadventures were about twice those of high school seniors who did not use these substances (16.3% for accidents; 20.2% for tickets or warnings).

Further analysis of the data revealed that 12th graders who were female, with two parents in the home, good grades, or strong religious commitments, were less likely to drive after using marijuana or alcohol. Those who reported above-average truancy, spent more evenings out for recreation, worked more hours, or drove more miles were more likely to engage in drugged driving.

African American students were more likely to drive after using marijuana than students of other races, but were not more likely to drive after drinking alcohol. Parental education, geographical region, and population density had no significant bearing on students’ attitudes toward drunk or drugged driving.

Vehicle accidents remain the number one cause of death among young Americans, and substance-impaired driving is one of the main culprits. Citing the data in their report, Dr. O’Malley and Dr. Johnston conclude that drunk and drugged driving is widespread among adolescents across schools and regions, and call for measures to reduce such risky behaviors.

Such efforts are already underway. A recent report prepared at NIDA’s request by experts in research, policy, and law enforcement under the auspices of the Institute for Behavior and Health has recommended to evaluate and improve drugged-driving laws, data collection, and educational programs, and to develop and standardize methods for drug testing in drivers. The goal of these proposed measures is to meet the target of the National Drug Control Strategy of the White House Office of National Drug Control Policy to reduce drugged driving by 10% by 2015.

Source

O’Malley, P.M.; Johnston, L.D. Driving after drug or alcohol use by U.S. high school seniors, 2001-2011. American Journal of Public Health 103(11): 2027-2034, 2013.

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