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How Does Marijuana Affect Driving?


Updated June 23, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Smoking Weed/Driving
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Question: How Does Marijuana Affect Driving?
Answer: Using marijuana can impair your judgment, motor coordination, ability to concentrate and slow your reaction time, and therefore can impair your driving skills. Anytime the skills needed to drive safely are impaired, even slightly, the chances of having a auto crash increase.

Research from the National Highway Traffic Safety Administration indicates that when drivers are killed in motor vehicle crashes, drugs other than alcohol are involved about 18% of the time. That means that one in six drivers killed in traffic mishaps are under the influence of drugs.

Another study found that of all drivers involved in auto crashes, 6.8% tested positive for THC, the active ingredient in marijuana. The same survey found that 21% of those drivers were above the legal level for blood alcohol content.

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Back to: Marijuana FAQ for Teens


National Institute on Drug Abuse. "Marijuana." DrugFacts Updated January 2014

National Institute on Drug Abuse. "Want to Know More?- Some FAQs about Marijuana." Marijuana: Facts for Teens Updated October 2013

National Institute on Drug Abuse. "Marijuana." Research Report Series Updated July 2012

The Partnership at DrugFree.org. "Marijuana." Drug Guide. Accessed April 2014.

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