Marijuana Fuels Increase in Drugged Driving

Marijuana Fuels Increase in Drugged Driving

Marijuana Fuels Increase in Drugged Driving

Marijuana Fuels Increase in Drugged Driving Most adults are aware that significant numbers of people drive a motor vehicle while under the influence of alcohol. However, public awareness does not typically focus as much on the numbers of people who drive while under the influence of various illegal or illicit drugs. Current evidence indicates that drugged driving does not occur as often as drunk driving. Still, drugged driving is just as dangerous (and illegal) as drunk driving, and a study published in January 2014 in the American Journal of Epidemiology indicates that the rate of drug-related motor vehicle fatalities rose substantially in the first decade of the 21st century.

The Basics

Broadly speaking, illegal and illicit drugs achieve their effects by altering the chemical balance inside the central nervous system, which includes both the brain and the spinal cord. As a rule, this alteration interferes considerably with a number of functions that are essential to maintaining awareness of one’s surroundings and properly controlling a car, truck, motorcycle or other vehicle. Examples of these essential functions include the ability to accurately coordinate muscle movements, the ability to respond appropriately to changing circumstances, the ability to focus and pay attention, the ability to make judgments and decisions, and the ability to process visual information. Drugs and medications specifically noted for their ability to interfere with the driving process include marijuana, cocaine, amphetamine, methamphetamine, opioid narcotics and sedative-hypnotics such as benzodiazepines.

Some states try to reduce drugged driving rates by imposing a legal standard for drug-related intoxication and impairment that roughly mirrors the standard used to identify people driving under the influence of alcohol. In addition, since the 1980s, many other states have adopted a much tougher definition of drugged driving that makes it illegal to drive with any amount of an illegal drug in your system, or any amount of the breakdown products that illegal drugs produce in the body over time.

How Many People?

The federal government tracks participation in drugged driving in a couple of ways. Each year, the Substance Abuse and Mental Health Services Administration sponsors a project called the National Survey on Drug Use and Health, which (among many other things) asks a nationwide sample of people age 12 and older to report whether they’ve driven under the influence of drugs in the last 12 months. In the latest year for which data is available (2012), just under 4 percent of all teenagers and adults admitted to participating in drugged driving at least once a year. This number represents a slight increase over the figures from 2011, but falls well below the 4.7 percent rate of drugged driving participation reported in the peak year of 2002.

Periodically, the National Highway Traffic Safety Administration conducts a project called the National Roadside Survey, which is designed (in part) to estimate the number of people in the U.S. who drive at night or on the weekends under the influence of drugs. According to the results of the most recent version of this survey (completed in 2007), over 16 percent of all weekend and nighttime drivers have a potentially impairing drug, prescription medication or non-prescription medication in their systems. People under the influence of illegal drugs make up almost two-thirds of this total.

Role in Fatal Accidents

In the study published in the American Journal of Epidemiology, researchers from Columbia University Medical Center used information gathered from six U.S. states to estimate the number of drivers nationwide who had drugs in their systems at the time of a fatal motor vehicle accident from 1999 to 2010. These states (West Virginia, New Hampshire, Illinois, Rhode Island, Hawaii and California) were chosen because they routinely perform blood tests on motor vehicle accident victims. All told, the researchers gathered data on 23,591 drivers. Over the entire period under study, 24.8 percent of these drivers died with some sort of drug in their systems. Significantly, the annual rate of drugged driving-related fatalities rose from a low of 16.6 percent in 1999 to a peak of 28.3 percent in 2010. The drug detected most frequently in fatal car crashes was THC, the active ingredient in marijuana.


The authors of the study published in the American Journal of Epidemiology note that the increase in drugged driving-related fatalities occurred among people of both genders, as well as among people of all ages. However, they also note that, in any given case, they could not fully determine whether the presence of drugs actually contributed to the events that led to a fatal crash.

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