Marijuana nearly doubles risk of collisions
February 9th, 2012
06:30 PM ET

Marijuana nearly doubles risk of collisions

We hear a lot about the hazards of drunk driving, but here's something else to put on your radar: A study in the British Medical Journal found that marijuana nearly doubles the risk of vehicle collisions.

Researchers conducted a systematic review of nine studies on the subject of marijuana and driving accidents, which incorporated almost 50,000 participants.

Alcohol impairs drivers' speed and reaction time, while cannabis affects spatial location, said Mark Asbridge, associate professor in the Department of Community Health and Epidemiology at Dalhousie University in Halifax, Nova Scotia.

Among impaired drivers, fatally injured drivers, and motor vehicle crash victims, marijuana is the most prevalent illegal drug that has been detected, according to the U.S. National Institute on Drug Abuse.

Drivers who have recently smoked marijuana may follow cars too closely, and swerve in and out of lanes, Asbridge said.

People who are impaired by alcohol often recognize that they're impaired by alcohol, but "people under the influence of cannabis often deny feeling impaired in any way," Asbridge noted.

It's not unusual for young people to go to a party and give the "designated driver" responsibility to the person who uses marijuana, Asbridge said.

"There clearly is a lot of misconception about the extent to which cannabis impairs performance," he said. "People just don't believe it."

As with alcohol, cannabis has different effects on different people. People metabolize cannabis in different ways.  Some inhale more than others.

The effects of cannabis tend to wear off within three to four hours, whereas alcohol can mess your thinking up longer. Depending on how much you drank, you may not be able to drive for up to 12 hours after you finish drinking.

If the driver is 35 or younger, there's a higher likelihood of marijuana consumption leading to collisions, previous research has found.

There's not enough information known about the effects of marijuana doses on collisions - in other words, what level of cannabis in a person's system correlates most with crashes.

And Asbridge's conclusions are based on observational studies, meaning there were no controlled conditions imposed to look at the effects of marijuana.

One problem in some of the existing research is that there was no measurement of cannabis within two to three hours of driving. Inactive metabolites of THC, a chemical found in marijuana,  can be present in urine for weeks or even a month after usage; marijuana usage so long ago would not affect driving performance or collisions. So Asbridge's group looked only at studies where there was a recent measurement. They also looked at studies that looked at both drivers who used marijuana and those who did not to compare the collision rate.

To deter marijuana usage just before driving, there is roadside testing for cannabis in Australia, western Europe and the United States, Wayne Hall of the University of Queensland in Australia said in an accompanying editorial.

Hall called for further research to evaluating the impact of roadside drug testing on preventing driver deaths connected to vehicle accidents and cannabis use.

soundoff (910 Responses)
  1. orlando italian restaurants

    Keep this going please, great job!


    April 7, 2021 at 11:49 | Report abuse | Reply
  2. best Italian Orlando

    Keep this going please, great job!


    April 7, 2021 at 12:33 | Report abuse | Reply
  3. Jake Barney Medwell

    908145 823549In the event you are interested in picture a alter in distinct llife, starting up usually the Los angeles Surgical procedures fat reduction method is a large movement so that you can accomplishing which normally concept. shed belly fat 64261

    April 8, 2021 at 02:36 | Report abuse | Reply
  4. fine dining Orlando

    thanks for sharing!


    April 8, 2021 at 05:30 | Report abuse | Reply
  5. best italian restaurants in orlando

    carry on, dont stop


    April 8, 2021 at 06:05 | Report abuse | Reply
  6. orlando italian restaurants

    such a great information for blogger i am a professional blogger thanks


    April 8, 2021 at 07:56 | Report abuse | Reply
  7. italian restaurants orlando

    very interesting , good job and thanks for sharing such a good blog.


    April 8, 2021 at 08:33 | Report abuse | Reply
  8. orlando italian restaurants

    Keep this going please, great job!


    April 8, 2021 at 09:15 | Report abuse | Reply
  9. fine dining Orlando

    This blog is great check it out


    April 8, 2021 at 11:08 | Report abuse | Reply
  10. best Italian Orlando

    A great read. I'll definitely be back.


    April 8, 2021 at 11:46 | Report abuse | Reply
  11. Window Washing Service Jefferson Park, Denver, CO

    Thank you, I've just been looking for information approximately this topic for a long time and yours is the greatest I have discovered so far. But, what in regards to the conclusion? Are you certain concerning the supply?


    April 8, 2021 at 13:06 | Report abuse | Reply
  12. Window Cleaning Service Barnum West, Denver, CO

    Usually I never comment on blogs but your article is so convincing that I never stop myself to say something about it. You're doing a great job Man,Keep it up.


    April 9, 2021 at 06:14 | Report abuse | Reply
  13. Best Window Washing Service Near Me Southmoor Park, Denver, CO

    Thank You for your information


    April 9, 2021 at 07:11 | Report abuse | Reply
  14. Window Washing Service Lower Highlands, Denver, CO

    thanks for sharing!


    April 9, 2021 at 07:40 | Report abuse | Reply
  15. Window Cleaning Service Montclair, Denver, CO

    Wow this blog is very nice!


    April 9, 2021 at 08:04 | Report abuse | Reply
  16. Best Window Washing Service Near Me Cheesman Park, Denver, CO

    Commenting on a blog is an art. Good comments create relations. You're doing great work. Keep it up.


    April 9, 2021 at 08:34 | Report abuse | Reply
  17. Window Cleaning Service Golden Triangle, Denver, CO

    Thanks for the information.


    April 9, 2021 at 09:28 | Report abuse | Reply
  18. Window Washing Service Platt Park, Denver, CO

    I'm not sure where you are getting your information, but great topic.


    April 9, 2021 at 10:10 | Report abuse | Reply
  19. Window Washing Service Southmoor Park, Denver, CO

    very interesting , good job and thanks for sharing such a good blog.


    April 9, 2021 at 12:36 | Report abuse | Reply
  20. Window Cleaning Service Cheesman Park, Denver, CO

    This is a very interesting article. Please, share more like this!


    April 9, 2021 at 13:39 | Report abuse | Reply
  21. Best Window Washing Service Near Me Barnum West, Denver, CO

    this is very informative and intersting for those who are interested in blogging field.


    April 9, 2021 at 14:32 | Report abuse | Reply
  22. Window Washing Service City Park, Denver, CO

    This blog is great check it out


    April 10, 2021 at 02:03 | Report abuse | Reply
  23. Window Cleaning Service East Colfax, Denver, CO

    Commenting on a blog is an art. Good comments create relations. You're doing great work. Keep it up.


    April 10, 2021 at 03:35 | Report abuse | Reply
  24. Window Washing Service Washington Park, Denver, CO

    Thanks for wonderful information I used to be in search of this info for my mission.


    April 10, 2021 at 05:28 | Report abuse | Reply
  25. Best Window Cleaning Service Near Me Five Points, Denver, CO

    This is a very interesting article. Please, share more like this!


    April 10, 2021 at 07:55 | Report abuse | Reply
  26. Window Washing Service River North Art District, Denver, CO

    A great read. I'll definitely be back.


    April 11, 2021 at 05:40 | Report abuse | Reply
  27. Best Window Cleaning Service Near Me Five Points, Denver, CO

    very interesting , good job and thanks for sharing such a good blog.


    April 11, 2021 at 06:39 | Report abuse | Reply
  28. Best Window Cleaning Service Near Me Capitol Hill, Denver, CO

    Your writing style has been surprised me. Thank you, quite great article.


    April 11, 2021 at 07:09 | Report abuse | Reply
  29. Best Window Cleaning Service Near Me Barnum West, Denver, CO

    nice information for a new blogger. it is really helpful


    April 11, 2021 at 07:37 | Report abuse | Reply
  30. Best Window Cleaning Service Near Me Lower Highlands, Denver, CO

    very interesting , good job and thanks for sharing such a good blog.


    April 11, 2021 at 08:06 | Report abuse | Reply
  31. vardenafil generic

    does canada sell generic vardenafil https://vegavardenafil.com/ generic levitra vardenafil 20mg

    April 12, 2021 at 02:52 | Report abuse | Reply
  32. sildenafil prescription discount

    buy sildenafil canada https://eunicesildenafilcitrate.com/ generic sildenafil 20 mg cost

    April 12, 2021 at 09:39 | Report abuse | Reply
  33. canadian weight loss pills

    canadian weight loss pills https://canadapillstorex.com/ canadian pills pharmacy

    April 12, 2021 at 11:47 | Report abuse | Reply
  34. where can i buy zithromax online

    azithromycin drug class https://zithromaxes.com/ zipak

    April 13, 2021 at 19:16 | Report abuse | Reply
  35. signature window washing

    carry on, dont stop


    April 15, 2021 at 11:15 | Report abuse | Reply
  36. 40 mg tadalafil

    tadalafil pills https://elitadalafill.com/ tadalafil gel

    April 16, 2021 at 23:08 | Report abuse | Reply
  37. zithromax for sale

    uses for zithromax https://zithromaxes.com/ z pak strength

    April 17, 2021 at 16:52 | Report abuse | Reply
  38. tadalafil 40 mg daily

    buy tadalafil us https://elitadalafill.com/ generic tadalafil united states

    April 17, 2021 at 19:51 | Report abuse | Reply
  39. vardenafil 40 mg

    us prices on vardenafil https://vegavardenafil.com/ vardenafil 20mg dosage

    April 18, 2021 at 06:03 | Report abuse | Reply
  40. parkinson and alprostadil

    alprostadil dosage https://alprostadildrugs.com/ alprostadil generic prices

    April 19, 2021 at 14:44 | Report abuse | Reply
  41. where can i buy alprostadil suppositories

    alprostadil injection instructions https://alprostadildrugs.com/ alprostadil gel online

    April 20, 2021 at 20:42 | Report abuse | Reply
  42. cialis canadian

    cialis, sale, canadian pharm. https://canadacialisstore.com/ canadian generic cialis 20mg

    April 23, 2021 at 05:10 | Report abuse | Reply
  43. viagra without a doctor prescription in canada

    ordering viagra from canada https://canadaviagrastore.com/ what is the brand name for the generic drug for viagra in canada

    April 23, 2021 at 09:56 | Report abuse | Reply
  44. do you need a prescription for viagra in canada

    generic viagra shipping from canada https://canadaviagrastore.com/ viagra sin recetas en farmacias de canada

    April 23, 2021 at 15:42 | Report abuse | Reply
  45. Forklift Cylinders Near Me

    When I initially commented I seem to have clicked the -Notify me when new comments are added- checkbox and now each time a comment is added I recieve four emails with the exact same comment. There has to be an easy method you can remove me from that service? Thanks!


    April 23, 2021 at 19:31 | Report abuse | Reply
  46. homes for sale fernan lake


    April 23, 2021 at 19:31 | Report abuse | Reply
  47. RV AC California

    Spot on with this write-up, I absolutely believe this amazing site needs much more attention. I’ll probably be back again to see more, thanks for the information!


    April 23, 2021 at 19:31 | Report abuse | Reply
  48. AC Repair Orlando

    Commenting on a blog is an art. Good comments create relations. You're doing great work. Keep it up.


    April 24, 2021 at 15:19 | Report abuse | Reply
  49. rv body repair

    I used to be able to find good info from your content.


    April 24, 2021 at 17:30 | Report abuse | Reply
  50. RV Collision Repair Near Me


    April 24, 2021 at 17:49 | Report abuse | Reply
1 2 3 4 5 6 7 8 9 10 11 12 13

Post a comment


CNN welcomes a lively and courteous discussion as long as you follow the Rules of Conduct set forth in our Terms of Service. Comments are not pre-screened before they post. You agree that anything you post may be used, along with your name and profile picture, in accordance with our Privacy Policy and the license you have granted pursuant to our Terms of Service.

About this blog

Get a behind-the-scenes look at the latest stories from CNN Chief Medical Correspondent, Dr. Sanjay Gupta, Senior Medical Correspondent Elizabeth Cohen and the CNN Medical Unit producers. They'll share news and views on health and medical trends - info that will help you take better care of yourself and the people you love.