College students drive, ride after marijuana, alcohol use

May 12, 2014

Bottom Line: Underage college students are likely to drive after using marijuana or drinking alcohol, and they also are likely to ride as passengers in the car of a driver who has used marijuana or been drinking.

Author: Jennifer M. Whitehill, Ph.D., of the University of Massachusetts, Amherst, and colleagues.

Background: Impaired driving is of great concern. College students are a population at increased risk of substance-related risk behavior, such as impaired driving. The authors examined underage college students' driving after using marijuana, driving after drinking or riding with a driver who used those substances.

How the Study Was Conducted: A telephone survey of 315 first-year college students (ages 18 to 20 years) from two large universities. The group of students was 56.2 percent female and 75.6 percent white.

Results: In the prior month, 20.3 percent of students had used marijuana. Among those using marijuana, 43.9 percent of male and 8.7 percent of female students drove after using the drug, while 51.2 percent of male and 34.8 percent of females rode as a passenger with a marijuana-using driver. Most of the students surveyed drank alcohol (65.1 percent), and of this group 12 percent of male and 2.7 percent of female students drove after drinking, while 20.7 percent of males and 11.5 percent of females reported riding in a car with a driver who drank. The authors found that driving after substance use was associated with at least a two-fold increase in the risk of being a passenger in a car with another user.

Conclusion: "Despite the limitations of our study, our findings are an important and timely contribution to the literature on older adolescents driving after drug use. They supplement our knowledge that marijuana use increases the risk of motor vehicle crashes by estimating how common it is for underage students to have taken this risk within the past 28 days."

(JAMA Pediatr. Published online May 12, 2014. doi:10.1001/jamapediatrics.2013.5300. Available pre-embargo to the media at

Editor's Note: This study was supported by a grant from the National Institutes of Health Common Fund and the National Institute of Child Health and Human Development. Please see article for additional information, including other authors, author contributions and affiliations, etc.

Editorial: Driving After Marijuana Use

In a related editorial, Mark Asbridge, Ph.D., of Dalhousie University, Nova Scotia, Canada, writes: "Of particular interest, although a higher proportion of students had drunk alcohol in the past month, rates of driving were much lower after drinking than after marijuana use. Study findings speak to the changing nature of impaired driving and bring needed attention to the issue of marijuana use before getting behind the wheel."

"Besides legislation, much work remains to be done to change social norms regarding the acceptability of using marijuana in the context of driving. Key to this goal is the increased education and awareness of varying stakeholders in public health, transportation and justice, as well as the general public, particularly young persons, among whom misconceptions about the impairing effects of marijuana on driving are common."

(JAMA Pediatr. Published online May 12, 2014. doi:10.1001/jamapediatrics.2014.83. Available pre-embargo to the media at

Editor's Note: Please see article for additional information, including other authors, author contributions and affiliations, etc.
Media Advisory: To contact author Jennifer M. Whitehill, Ph.D., call Janet Lathrop at 413-545-2989 or email To contact editorial author Mark Asbridge, Ph.D., call Allison Gerrard at 902-494-1789 or email

The JAMA Network Journals

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