Stoned Driving Nearly Doubles the Risk of a Fatal Crash

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People who drive within three hours of smoking marijuana are at nearly twice the risk of being in an accident that leads to serious injury or death, compared with sober drivers, according to a new review of the research.

About 4% of the American adult population — nearly 11 million people — report having driven under the influence of a drug other than alcohol, overwhelmingly marijuana.

Prior research on the risks of stoned driving has been mixed, with about half of the studies finding that marijuana raises the chance of crashing and the rest showing either no effect or a slight decrease in risk. Driving simulation studies with experienced marijuana users suggest that when people have consumed high doses of the drug, there’s an increased risk of accident, but that, unlike with alcohol, users are aware of their impairment and tend to drive more cautiously, rather than with greater recklessness.

MORE: Why Pot Smokers Are Paranoid

For the new review, published in BMJ, Canadian researchers pooled the results of nine well-designed, high-quality studies that included nearly 50,000 drivers involved in crashes in multiple countries. They found that recent marijuana use was associated with a 92% increased risk of fatal or near-fatal accidents. The better the quality of the study, the more likely it was to show an increase in marijuana-related risk.

The risk for minor collisions, however, was not raised significantly — possibly reflecting the fact that many stoned drivers attempt to be more cautious and can therefore compensate for some risks. That compensation may fail, however, when quick reflexes are most needed.

While driving stoned is clearly risky — and combining marijuana with alcohol is even more dangerous — drunk driving remains a bigger hazard on the road. Driving with a blood alcohol concentration of .08 — the legal limit — nearly triples the risk of crashing; a blood alcohol concentration of .10 almost quintuples it. Although drunk driving deaths have dropped by more than half since 1982, they still represent about one-third of all auto fatalities and kill about 11,000 people annually.

MORE: How Medical Marijuana Laws May Cut Traffic Deaths

Determining the precise role of marijuana in traffic deaths is more complicated than studying alcohol because blood levels of marijuana’s active ingredient, THC, are not always directly linked with levels of impairment the way blood alcohol levels are.

Interestingly, researchers have also found that states that legalize medical marijuana have fewer fatal car crashes, largely because of a decline in drunk driving. In other words, people may be substituting marijuana for alcohol — and while it’s not advisable to drive under the influence of either — the net result, when it comes to traffic deaths, could be a reduction in harm because smoking pot raises the crash risk less than drinking does.

Maia Szalavitz is a health writer at TIME.com. Find her on Twitter at @maiasz. You can also continue the discussion on TIME Healthland’s Facebook page and on Twitter at @TIMEHealthland.

6 comments
regularjoe
regularjoe

Blood tests are performed on crash fatalities to determine use of alcohol and other drugs.  Marijuana metabolites are stored in fat cells and you can test positive a month or more after your last smoke.  It does not determine whether or not marijuana was a cause of the crash.

Anecdotal evidence says that Stoned drivers drive slower if at all(glued to couch, delivery pizza).  There are saliva tests in development but I think that regular road side sobriety tests should be sufficient.  After all, there is no roadside test for the plethora of opiates that are prescribed daily.

JohnSmith9
JohnSmith9

@regularjoe Couple of things you missed there, buddy. The article cites researchers as saying that "recent marijuana use was associated with a 92% increased risk of fatal or near-fatal accidents." So clearly they are able distinguish time frames here, and we're not talking metabolites stored in fatty tissues from months ago. Also, driving slower is not necessarily safer. As the article states "The risk for minor collisions, however, was not raised significantly — possibly reflecting the fact that many stoned drivers attempt to be more cautious and can therefore compensate for some risks. That compensation may fail, however, when quick reflexes are most needed." In other words, not reacting fast enough in critical situations can be deadly.

HempShare
HempShare

@JohnSmith9 @regularjoe  John "buddy" you forgot to do your research rather than just reading the copy edited by the CIA information officer who works at the Times.

http://hempshare.org/wp-content/uploads/2012/10/DOT-HS-808-078.pdf

The NTHSA found that "High Driving" at its worst is equivalent to 0.8% BAC.

The NTHSA has attempted this study on U.S. soil twice since this time (presumably because they didn't get the negative results they planned on), and apparently they just can't get people stoned enough to make them dangerous drivers.

I would gladly get hit by a stoner in his Subaru rather than some alcoholic in a Hummer - ANY DAY!

JohnSmith9
JohnSmith9

@@HempShare

So what it comes down to for you is that stoners drive around in Subaru's whereas alcoholics typically drive Hummers? lol Have you seen Entourage? Apparently stoners can drive big SUVs too.  

A BAC of 0.08% is very high, and under federal law a person with a blood alcohol level that high is deemed to be driving under the influence. Some states, and many countries, have limits that are lower than 0.08%. And for good reason: a BAC that high drastically increases your risk of getting involved in an accident.

I honestly don't care what poison people prefer, be it alcohol, cannabis or cocaine, so you can spare me your paranoid conspiracy theories, but what I do take issue with is when they endanger other people's lives by taking it out on the road. And I don't care what you drive: Subarus can still kill.