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Marijuana Use Doubles Risk of Car Crash, Study Says

Cannabis is the most widely used illicit substance globally and recent statistics have shown a significant increase in use across the world. Rates of driving under influence have also increased, the paper said.

  • Feb 13, 2012

Drivers who consume marijuana within three hours of driving are nearly twice as likely to cause a vehicle collision as those who are not under the influence of drugs or alcohol, according to a paper published recently in the British Medical Journal.

The paper's authors reviewed nine studies with a total sample of 49,411 people to determine whether the consumption of cannabis increases the risk of a motor vehicle collision.

This is the first review to look at various observational studies concerned with the risk of vehicle collision after the consumption of cannabis. Previous studies have failed to separate the effects of alcohol and other substances from the use of cannabis, resulting in a lack of agreement, according to BMJ.

Cannabis is the most widely used illicit substance globally and recent statistics have shown a significant increase in use across the world. Rates of driving under influence have also increased, the paper said. A roadside survey carried out in Scotland in 2007 showed that out of 537 drivers tested, 15 percent aged 17-39 admitted to having consumed cannabis within 12 hours of driving.

All motor vehicle collisions involved in the study took place on a public road and involved one or more moving vehicles such as cars, vans, sport utility vehicles, trucks, buses, and motorcycles. Results were taken through blood samples or direct self-report.

Results showed that if cannabis is consumed before driving a motor vehicle, the risk of collision is nearly doubled. Previous results have also found that there is a substantially higher chance of collision if the driver is aged 35 or younger.

The authors concluded that the consumption of cannabis impairs motor tasks important to safe driving, increasing the chance of collisions, and that future reviews should assess less severe collisions from a general driving population.

Comments

Mon, Apr 9, 2012

The vast majority of commenters seem to defend the use of a mood and perception altering substance in conjunction with or shortly prior to sitting at the controls of a 3000-5000 pound vehicle. Some even claim to be EH&S professionals. I find this disturbing to say the least! I thought after a 35-year EH&S career I could no longer be amazed at the self-justification capability of the human mind. Guess I was wrong!

Thu, Apr 5, 2012 Ricardo

Just the first paragraph of this article is so stupid that I won't even bother reading the rest of it. To say that you are more likely to be in an accident if you smoke marihuana than if you drink alcohol or use other drugs (like heroin?)is ridiculous. What a coincidence, now that many states are moving to legalize pot all of a sudden a bunch of studies against it come out. Leave it to special interests to continue this attack. Not only can pot help with many medical conditions now treated with pharmadrugs with no serious side effect, but the hemp can compete with many synthetic products. No wonder the attack!

Tue, Feb 14, 2012

Sorry Barbarian you are so out of touch with the real world. I know more people who smoke or have smoked marijuana than people who haven't. I also don't believe I'm a "burned out pot head" as you put it. Marijuana does not affect your life long term. Only if that is what you choose to do. I am The Maintenance Director, Safety Director, and Safety Committee Chairman with multiple certificates and degrees. I work for a multi- million dollar company. If that sounds like a burned out pot head to you then you must be smoking right now. Furthermore I haven't smoked for over 5yrs and you shouldn't be judging other people. You seem to not really know what marijuana is or it's effects.

Mon, Feb 13, 2012 Barbarian Maryland

To Bill and the un-named medical marijuana patient - to claim that statistics gleaned from nine studies involving 49,411 people are “so not true” or “bunk” because they aren’t compatible with your personal experience is incredibly ignorant. You make yourself sound like burned out pot heads. And Joe, it may make you more cautious, (again with the personal experience) but it slows down your reaction time which is undesirable when operating a vehicle.

I have nothing against marijuana use and think we would all be better off if the government would get out of the business of policing it, with the exception of the prohibition of driving while impaired, which should apply equally to any substance.

Mon, Feb 13, 2012

I quote the author: "In seven of the nine studies the risk of a crash went up when drivers had smoked marijuana within a few hours of the accident. The other two studies found that the risk of having a collision while under the influence was lower than that of sober drivers."

Mon, Feb 13, 2012

A recent survey has determined that 67% of the people driving on American highways have smoked marijuana in the prior 24 hour period. A further 52% of that 67% "waked and baked" and yet another 73% of the 67% of the 52% are smoking marijuana as they are driving now......... (a full 87% of the people that quote statistics just make them up as they go along...the other 13% are full of themselves

Mon, Feb 13, 2012

My study shows that people who consume dairy products before operating a motor vehicle are just as likely to be in an accident as those subjects who did not consume dairy products before operating a motor vehicle.

Mon, Feb 13, 2012 Charles Wilson Seattle

This issue begs for general system type studies. Back when I lived in Texas, alcohol sales silliness forced folks to drink in "clubs" and drive home for inability to buy their beverages and use it at home AND there was no open container law -- it was legal to drink and drive. If marijuana use doubles the accident rate of smokers who drive BUT keeps 95% of users out of the car (until the snack supply is exhausted), highway deaths may be avoided by subsidy of home pizza delivery and marijuana use. What if marijuana kept folks from drinking?? Probably a lousy theory but there is a point to make. Brain-liquifying ear buds and digestion aiding woofers might be a MUCH greater public safety hazard but this may reveal my prejudice to music choices more than anything else. Measurements of hazard and success must be done carefully to be valid in issuing restrictions.

Mon, Feb 13, 2012 Bill Suncook NH

This article is so not true. I've smoked marijuana constantly for over 30yrs and never had an accident because of it. I can't even name one person that I've smoked with in all that time whom have had an accident because of marijuana. Alcohol yes, weed no. The real problem is talking/texting on a cell phone.

Mon, Feb 13, 2012 Brother Rog

This is still a safety issue. Twice as likely to have a collision is something to be concerned about and needs further evaluation. I am interested, however, if the study includes users of Marijuana that also had a alcoholic beverage. What are the effects then? As one goes with the other more than not. Or does it? Something to look into I believe. Remember this is the first review, and is not in any way conclusive, or grounds for rules laws, or regulation. This needs to be studied out. And then the study needs to be repeated by a peer organization to comfirm the results. Only then, should we be printing articles and thumping our chest. Otherwise, the article is viewed as "some filler for a slow safety news day". OH&S news needs to be more than "forwarding an email." Safety takes effort and work. Be Safe.

Mon, Feb 13, 2012 Need More Info

I appreciate Joe's comments above but I'd like OH&S to check these figures. I also want to know why the first metric mentioned is 3 hours and the second is 12. Finally, I want to know about pot's involvement in industrial accidents.

Mon, Feb 13, 2012

I am a medical marijuana patient and I can say that the study is bunk. I have a perfect driving record and no accidents. First, the effects of THC do not last beyond 3-4 hours (if even that), so the 12-hour reference has no practical meaning or useful application here. Moreover, because marijuana is the most widely used drug in the world today (other than alcohol), the study's findings are fundamentally flawed. We are fighting the wrong beast here.

Mon, Feb 13, 2012 Joe Earth

To put this in perspective: Driving at the legal intoxication limit of .07% BAC, you are over 10 times more likely to be involved in an accident. If driving while texting you are 8 times more likely to be in an accident. If driving while talking on a cell phone or to passengers you are 4 times more likely to have a accident. If using marijuana you are 2 times more likely to be in an accident, about the same as if you were listening to the radio. Marijuana doesn't remove your inhibitions like alcohol, it makes you more cautious.

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