Federal Study: THC-Positive Drivers Not More Likely To Be Involved In Motor Vehicle Crashes

  • by Paul Armentano, NORML Deputy Director February 9, 2015

    Federal Study: THC-Positive Drivers Not More Likely To Be Involved In Motor Vehicle Crashes Drivers who test positive for the presence of THC in blood are no more likely to be involved in motor vehicle crashes than are drug-free drivers, according to a federally sponsored case-control study involving some 9,000 participants. The study, published Friday by the United States National Highway Traffic Safety Administration (NHTSA), is the first large-scale case-control study ever conducted in the United States to assess the crash risk associated with both drugs and alcohol use by drivers.

    Authors reported that drivers who tested positive for any amount of THC possessed an unadjusted, elevated risk of accident of 25 percent (Odds Ratio=1.25) compared to controls (drivers who tested negative for any drug or alcohol). However, this elevated risk became insignificant (OR=1.05) after investigators adjusted for demographic variables, such as the drivers’ age and gender. After researchers controlled for both demographic variables and the presence of alcohol, THC-positive drivers’ elevated risk of accident was zero (OR=1).

    By contrast, researchers reported that drivers who tested positive for low levels of alcohol possessed a statistically significant risk of accident, even after controlling for demographic variables (e.g., Drivers with a BAC of 0.03 possessed a 20 percent greater risk of motor vehicle accident [OR=1.20] compared to controls). Drivers with BAC levels of 0.05 possessed a greater than two-fold risk of accident (OR=2.07) while motorists with BAC levels of 0.08 possessed a nearly four-fold risk of accident (OR=3.93).

    Researchers did not analyze drivers’ THC levels to similarly estimate whether higher or lower THC levels may impact crash risk in a dose-dependent manner, as has been previously reported in some separate analyses of fatal crash data.

    Authors concluded, “This finding indicates that these other variables (age, gender, ethnicity, and alcohol use) were highly correlated with drug use and account for much of the increased (crash) risk associated with the use of illegal drugs and THC.”

    The study’s finding contradict allegations by NIDA and others that “marijuana use more than doubles a driver’s risk of being in an accident,” but are largely consistent with those of a 2013 literature review published in the journal Accident Analysis and Prevention which reported that cannabis-positive drivers did not possess a statistically significant risk of a either fatal accident or a motor vehicle accident causing injury.

    See NORML’s white paper on cannabis and psychomotor performance here.

    19 responses to “Federal Study: THC-Positive Drivers Not More Likely To Be Involved In Motor Vehicle Crashes”

    1. Mark Lee BSHA/HM cannabis specialist and activist. says:

      I am glad you posted this as the Colorado Marijuana Authority report was just released to the public. The accompanying article is something for the opposition to run with like there is no tomorrow!!!
      As a published author, I am writing a rebuttal to the study the Colorado Authority admits uses research from illegal times, from NIDA, and assumptions of auto injury when they have no idea of other drug involvement especially fatigue or alcohol.
      My wife is a DHS Administrator who could gather far better data if a quick visit were required. Then they could have accurate, 100% verified, and reliable data rather than the 3,974 that returned survey’s. I do not know Colorado’s exact population, but I know at least that lived in my immediate area when I lived in SE Denver.
      As other states will be using this model, let’s get my cannabis supporting wife involved and kick federal public health workers out of their program, as they stated this administration was responsible for a great deal of the information they were forced into publishing. If they are going to allow the publication of despotic dis-information, I think Colorado should spend some of that tax money into people who could give them 100% accuracy, as part of a team that will make real contacts with 100% of consumers and be an advocate they can call without fear of reprisals. Something they should have had from day one with the Nation looking toward them for a future for cannabis!!!

    2. Dave Evans says:

      Why do we need “science” to show us what our eyes already are telling us? Marijuana’ed drivers are not more dangerous. Just fucking stop with the non-logical comparisons to alcohol already!!!!!!!! The only fucking connection, which again you can see with you own eyes, is people at parties like to drink alcoholic beverages and smoke weed. People crash their cars after partying because they drank alcohol which shuts down you nervous system. The marijuana does not shut down the nervous system and it cannot contribute to crashes. Modifying you consiousness is not the same thing as turning it off. Marijuana slightly modifies while alcohol turns off. These are two completely different effects.

      It is all just a stupid association with drunks crashing their cars and sometimes those drunks also smoked weed. It has nothing to do with the marijuana!!!!!!! It is not able to produce effects on a human counter to its own chemistry!!!!!

      At this point, it isn’t just an “association” it is an “over association”. Fiction as fact.

    3. shawn kearney says:

      While I am a bit skeptical, and find stoned driving a very terrifying experience, I’ve never been in an accident while stoned either.

    4. Miles says:

      “marijuana use more than doubles a driver’s risk of being in an accident,” according to the prohibitionist organization known as NIDA.

      First, I have never believed this BS!

      Secondly, even if it is true, then if my risk of being in an accident is doubled or even quadrupled it is not a reason to be concerned if your risk is close to zero to begin with! Basic math shows us that zero times anything is zero.

      Third, my practical experience tells me that driving under the influence of cannabis is completely safe as long as you’re a good driver to begin with. I’ve driven under the influence of cannabis more than a thousand times and have a perfectly clean driving record!!! Well, except for one minor fender bender. I hit someone from behind after they suddenly slammed on their brakes. The interesting thing is, I was completely straight when it happened. That was about 20 years ago and no one was hurt.

    5. Fireweed says:

      I keep saying this but:
      1) back “in the day” I had a car for 13 years that I put almost 300,000 miles on, and a huge percentage of that was stoned. Not one accident until I was driving in downtown Columbus and another car changed lanes and pushed me out of my lane, up on the sidewalk. I narrowly missed a bus stop with people in it.

      can’t remember if I was high in that incident (though I definitely had metabolites in my system) but on three other occasions when I WAS driving stoned, I missed a head-on crash when an oncoming driver swerved into MY lane and it was ME that avoided an accident. ONe car had actually lost control and bounced across the grass median into my lane, another was coming around a blind curve, and the other was because it was icy and that car swerved to avoid the car in front of it that had braked. bad drivers abound but I’m not one of them.

    6. Timothy Overedowd says:

      @shawn kearney:
      February 10, 2015 at 2:25 am
      – –

      the fact that you find stoned driving
      a “terrifying experience”,
      (I’m also apprehensive to drive when high),
      demonstrates that the cannabis high ITSELF
      is its own DUI deterrent, (UNLIKE alcohol).
      “I don’t want to drive anywhere, I feel too baked!!!”
      vs. alcohol:
      “I’m okay to drive, I’ve only had a few drinks!”].

    7. Galileo Galilei says:

      People on THC are aware of their impairment and compensate for it. People on ethyl alcohol endanger us all.

      Bars with parking lots – think about it.
      Marijuana ‘coffeeshops’ appear to be a much safer alternative.

    8. Drummer Man says:

      People, this article refers to THC in the system, not driving stoned, I believe.

      I personally think we shouldn’t drive stoned, period, simply out of respect for others’ fears. Because the more we can demonstrate that cannabis consumers ARE responsible adults who respect their fellow citizens and use cannabis safely in whatever capacity they choose (be it medicinal or recreational), the better it is for the cause.

      Personal experience or ability to drive stoned aside, this small concession will go a long way towards assuaging the fears of those who don’t have a strong opinion on legalization one way or the other. Don’t be the prohibitionists’ ‘example’ of why pot is ‘bad’. Prove them wrong, instead. It’s much more gratifying.

      That’s just my 2 cents. Have an awesome day everyone!

    9. Julian says:

      Awww Maaaan! Now how are law enforcement suppose to artificially line city budgets? I know!; Meth outbreak! Zombie Apocalypse! (Lol) What will they think of next? Prohibitionists are running out of false justifications for unconstitutional enforcement of marijuana policy faster than the DEA can raid the wrong house. It appears as though the ONDCP is no longer in tight control of our domestic federal research of marijuana anymore.

    10. chrissy says:

      Well I have road with both drunk & someone stoned. Would feel a hell alot safer with the stoner. It would be a lot more comical. Instead of the drunk that wants to fight, steal something.