- Canadian researchers have concluded that people who smoke marijuana within three hours of driving are nearly twice as likely to get in a serious car crash.
- The research included nine observational studies, with a sample size of nearly 50,000 accident victims.
- It was published in the February 9 issue of the British Medical Journal.
LONDON — Medicinal marijuana users might want to stay away from their car keys after indulging. Canadian researchers have found that people who smoke marijuana within three hours of driving are twice as likely to have a serious car accident.
The study, published in the February 9 issue of the British Medical Journal, was led by associate professor Mark Asbridge from Halifax's Dalhousie University. Asbridge and his research team analyzed nine observational studies with a sample size of nearly 50,000 accident victims, concluding that the pooled risk of vehicle collision under the influence of cannabis is 1.92 times the risk of crashing while driving unimpaired. The researchers concluded that marijuana impairs performance of the cognitive and motor tasks necessary for safe driving.
The research shows that there is a relationship between the presence of tetrahydrocannabinol (THC) in the blood and motor vehicle accidents, although the exact level of danger is unknown due to the fact that many of the studies simply measured for the presence of the THC, not its concentration.
Only three of the studies actually measured precise levels of THC in the blood, and a correlation between crash risk and THC concentrations was supported.
"Although we did not examine dose effects on the risk and severity of collisions, studies of fatally injured drivers found higher amounts of tetrahydrocannabinol in the blood. [THC] concentrations might also be important, with minor collisions more likely than fatal collisions to involve drivers with lower concentrations of cannabis," the experts reported.
Hartford Hospital and the University of Iowa Carver College of Medicine published a study back in 2010 with the opposite results, albeit with a smaller sample size of just 85 drivers.
Read the latest study here.
Inside Line says: A fascinating study that is one of the largest of its kind.
Add A Comment »
travai says:
08:27 AM, 02/22/2012
Newsflash: Marijuana Smokers Claim Unflattering Study of Marijuana Usage Is Biased
agentorange says:
11:34 AM, 02/21/2012
"...and next on Obvious TV, reaction to the controversial study that says water is wet."
rats says:
08:54 PM, 02/20/2012
@ lmbvette
Althought streetmoney21 is a bit annoying he does have a point.
Research is about isolating the relevant variables and finding evidence to back them up. But this study seems like it's susceptible to confusing causation vs. correlation due to not having a pretty important variable... the THC concentration levels.
The other major problem is that it's not a controlled experiment, they just went through accident data.
The reason I find this study suspect is because all the other studies which controlled environments I've read came up with much different results. The impairments were smaller, much more than alcohol and sleepiness to the point where it was deemed borderline safe.
jeremy0818 says:
07:53 PM, 02/20/2012
"people who smoke marijuana within three hours of driving are nearly twice as likely to get in a serious car crash"
shouldn't it be
"people who drive within three hours of smoking marijuana are twice as likely to have a serious car crash"?
Otherwise that means they either stopped driving and went to smoke, then sometime after smoking they have higher chance of getting hit by a car as a pedestrian
or
Somehow smoking marijuana within three hours (thus before or after) of driving is some sort of magical formula which curses the person to have higher chance of car crash, regardless of being a driver or a pedestrian
Or is this how they say things in Canada?
theinsurgent says:
06:05 PM, 02/20/2012
Stooopid Canadians.
urbanxj says:
04:13 PM, 02/20/2012
Legalize it. Tax it. Prosecute driver's to the same degree as drunks.
There, problem solved. I just made the world a better place.
93aero says:
03:40 PM, 02/20/2012
Im not surprised. But its not like alcohol is doing any better in the "you can drive when you do it" category. Besides, you have to be smart enough to get around this problem, so overt its covert, is not something you'd wanna do.
calspecial68 says:
02:27 PM, 02/20/2012
One of the best drivers I've met smokes all day every day. Granted he's no professional driver, but he always takes care when driving on the street. He pays way more attention than all those distracted drivers with their phones ablaze. The worst thing he does IMO when driving is do so without proper maintenance or expired stickers, which is no reflection of driving performance merely poor vehicle ownership and not being affluent enough to keep up with his car. I know, I know; Statistics mean nothing to the individual, but this is just my personal experience.
streetmoney21 says:
01:01 PM, 02/20/2012
@lmbvette lol typical of a rim-jobber to think people are not educated because they disagree with research. How many times do other studies come out to refute what was previous thought of as truth? You & travai should try to read more instead of using your heads as a butt-plugs for your favorite zoo animal. I know plenty of people who have smoked weed for years on a regular bases and have never had an accident to this very day.
The problem with the study is that THC remains in fat cells of the body for long periods of time so who's to say that a particular amount will cause you to have an accident. I guess if you eat to many Mc Doubles from Mac Donald's you could have an accident because you could fall asleep at the wheel from eating too much.
Accidents are caused by poor judgement period. That's not to say your judgment cannot be affected by outside forces like a cell phone, too much prescription medication, mixing medication, looking at you ipod for a song, digging for coins in an ash tray while driving down the street, or day dreaming while driving.
The only thing this study concludes is that poor judgement is in fact the leading cause of an auto accident and people like you need to read more before you come up with a lame ass response with no facts to back just to make yourself feel important.
erik25 says:
11:55 AM, 02/20/2012
Know someone who drives already 25 years smoking pot and no accident,1 day 1/4 inch of snow in North Carolina and saw already 5 accidents on my way to work,they better can see at the yearly inspection that people wear some good tires under there car than taxpayers have to pay for this study on drugs.There are more accidents happening because of the "legal" drug use as alcohol and use of precription drugs.Don't need a study for this and this one is for free! Lol.