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NIDA InfoFacts: Drugged Driving

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What is Drugged Driving?

"Have one [drink] for the road" was, until recently, a commonly used phrase in American culture. It has only been within the past 20 years that as a Nation, we have begun to recognize the dangers associated with drunk driving. Through a multipronged and concerted effort involving many stakeholders, including educators, media, legislators, law enforcement, and community organizations such as Mothers Against Drunk Driving, the Nation has seen a decline in the numbers of people killed or injured as a result of drunk driving. It is now time that we recognize and address the similar dangers that can occur with drugged driving.

In 15 states (Arizona, Georgia, Indiana, Illinois, Iowa, Michigan, Minnesota, Nevada, North Carolina, Ohio, Pennsylvania, Rhode Island, Utah, Virginia, and Wisconsin), it is illegal to operate a motor vehicle if there is any detectable level of a prohibited drug, or its metabolites, in the driver's blood. Other state laws define "drugged driving" as driving when a drug "renders the driver incapable of driving safely" or "causes the driver to be impaired."

The principal concern regarding drugged driving is that driving under the influence of any drug that acts on the brain could impair one's motor skills, reaction time, and judgment. Drugged driving is a public health concern because it puts not only the driver at risk, but also passengers and others who share the road.

How Many People Take Drugs and Drive?

The National Highway Traffic Safety Administration (NHTSA) reports that more than 17,000 people were killed in alcohol-related crashes in 2006.1 Studies also have found that drugs are used by 10 to 22 percent of drivers involved in crashes, often in combination with alcohol.

According to the 2006 National Survey on Drug Use and Health, an estimated 10.2 million people age 12 and older reported driving under the influence of illicit drugs during the year prior to being surveyed.2 This corresponds to 4.2 percent of the population age 12 and older, similar to the rate in 2005 (4.3 percent), but lower than the rate in 2002 (4.7 percent). In 2006, the rate was highest among young adults age 18 to 25 (13.0 percent).2 In addition:

  • In 2006, an estimated 13.3 percent of persons age 12 and older drove under the influence of an illicit drug or alcohol at least once in the past year. This percentage has dropped since 2005, when it was 14.1 percent. The 2006 estimate corresponds to 32.8 million persons.2
  • Driving under the influence of an illicit drug or alcohol was associated with age. In 2006, an estimated 7.3 percent of youth age 16 drove under the influence. This percentage steadily increased with age to reach a peak of 31.8 percent among young adults age 22. Beyond the age of 22, these rates showed a general decline with increasing age.2
  • Also in 2006, among persons age 12 and older, males were nearly twice as likely as females (17.6 percent versus 9.3 percent) to drive under the influence of an illicit drug or alcohol in the past year.2

In recent years, drugs other than alcohol that act on the brain have increasingly been recognized as hazards to road traffic safety. Some of this research has been done in other countries or in specific regions within the United States, and the prevalence rates for different drugs vary accordingly. Overall, the research indicates that marijuana is the most prevalent illegal drug detected in impaired drivers, fatally injured drivers, and motor vehicle crash victims. Other drugs also implicated include benzodiazepines, cocaine, opiates, and amphetamines.3

A number of studies have examined illicit drug use in drivers involved in motor vehicle crashes, reckless driving, or fatal accidents. For example:

  • One study found that about 34 percent of motor vehicle crash victims admitted to a Maryland trauma center tested positive for “drugs only”; about 16 percent tested positive for “alcohol only.” Approximately 9.9 percent (or 1 in 10) tested positive for alcohol and drugs, and within this group, 50 percent were younger than age 18.4  Although it is interesting that more people in this study tested positive for “drugs only” compared with “alcohol only,” it should be noted that this represents one geographic location, so findings cannot be generalized. In fact, many studies among similar populations have found higher prevalence rates of alcohol compared with drug use.5
  • Studies conducted in several localities have found that approximately 4 to 14 percent of drivers who sustained injury or died in traffic accidents tested positive for delta-9-tetrahydrocannabinol (THC), the active ingredient in marijuana.6
  • In a large study of almost 3,400 fatally injured drivers from three Australian states (Victoria, New South Wales, and Western Australia) between 1990 and 1999, drugs other than alcohol were present in 26.7 percent of the cases.7 These included cannabis (13.5 percent), opioids (4.9 percent), stimulants (4.1 percent), benzodiazepines (4.1 percent), and other psychotropic drugs (2.7 percent). Almost 10 percent of the cases involved both alcohol and drugs.

Teens and Drugged Driving

  • According to the NHTSA, vehicle accidents are the leading cause of death among young people age 16 to 20.1 It is generally accepted that because teens are the least experienced drivers as a group, they have a higher risk of being involved in an accident compared with more experienced drivers. When this lack of experience is combined with the use of marijuana or other substances that impact cognitive and motor abilities, the results can be tragic.
  • Results from NIDA's Monitoring the Future survey indicate that, in 2006, more than 13 percent of high school seniors admitted to driving under the influence of marijuana in the 2 weeks prior to the survey.8
  • The 2004 State of Maryland Adolescent Survey indicates that 13.5 percent of the State’s licensed adolescent drivers reported driving under the influence of marijuana on three or more occasions.9

Why is Drugged Driving Hazardous?

Drugs act on the brain and can alter perception, cognition, attention, balance, coordination, reaction time, and other faculties required for safe driving. The effects of specific drugs of abuse differ depending on their mechanisms of action, the amount consumed, the history of the user, and other factors.


THC affects areas of the brain that control the body’s movements, balance, coordination, memory, and judgment, as well as sensations. Because these effects are multifaceted, more research is required to understand marijuana's impact on the ability of drivers to react to complex and unpredictable situations. However, we do know that:

  • A meta-analysis of approximately 60 experimental studies, including laboratory, driving simulator, and on-road experiments, found that behavioral and cognitive skills related to driving performance were impaired in a dose-dependent fashion with increasing THC blood levels.10
  • Evidence from both real and simulated driving studies indicates that marijuana can negatively affect a driver's attentiveness, perception of time and speed, and the ability to draw on information obtained from past experiences.
  • Research shows that impairment increases significantly when marijuana use is combined with alcohol.11
  • Studies have found that many drivers who test positive for alcohol also test positive for THC, making it clear that drinking and drugged driving are often linked behaviors.1

Other Drugs

  • Prescription drugs: Many medications (e.g., benzodiazepines and opiate analgesics) act on systems in the brain that could impair driving ability. In fact, many prescription drugs come with warnings against the operation of machinery—including motor vehicles—for a specified period of time after use. When prescription drugs are taken without medical supervision (i.e., when abused), impaired driving and other harmful reactions can also result.

In short, drugged driving is a dangerous activity that puts us all at risk.

1.  National Highway Traffic Safety Administration. Traffic Safety Facts Research Note. Washington, DC, 2007. U.S. Department of Transportation Report No. DOT HS 810 821.

2.  Substance Abuse and Mental Health Services Administration. 2006 National Survey on Drug Use and Health. Rockville, MD, 2007.

3.  Soderstrom CA, Dischinger PC, Kerns TJ, Kufera JA, Scalea TM. Epidemic increases in cocaine and opiate use by trauma center patients: Documentation with a large clinical toxicology database. J Trauma 51:557–564, 2001.

4. Walsh JM, Flegel R, Cangianelli LA, Atkins R, Soderstrom CA, Kerns TJ. Epidemiology of alcohol and other drug use among motor vehicle crash victims admitted to a trauma center. Traffic Inj Prev 5(3):254–260, 2004.

5.  Kelly E, Darke S, Ross J. A review of drug use and driving: Epidemiology, impairment, risk factors, and risk perceptions. Drug Alcohol Rev 23(3):319–344, 2004.

6.  Ramaekers JG, Berghaus G, van Laar M, Drummer OH. Dose related risk of motor vehicle crashes after cannabis use. Drug Alcohol Depend 73(2):109–119, 2004.

7.  Drummer OH, Gerostamoulos J, Batziris H, et al. The incidence of drugs in drivers killed in Australian road traffic crashes. Forensic Sci Int 134:154–162, 2003.

8.  O’Malley PM, Johnston LD. Drugs and driving by American high school seniors, 2001–2006. J Studies Alcohol Drugs 68(6):834–842, 2007.

9.  Maryland State Department of Education. 2004 Maryland Adolescent Survey. Available at:

10.  Berghaus G, Sheer N, Schmidt P. Effects of Cannabis on Psychomotor Skills and Driving Performance–A Meta-Analysis of Experimental Studies. In: Kloeden CN and McLean AJ, eds. Proceedings of the 13th International Conference on Alcohol, Drugs and Traffic Safety. Adelaide, Australia: The University of Adelaide, NHMRC Road Accident Research Unit, pp. 403–409, 1995.

11.  National Highway Traffic Safety Administration. Marijuana and alcohol combined severely impede driving performance. Ann Emer Med 35(4):398–399, 2000.

Revised 4/08
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