Everybody remembers their first car like it was yesterday.
Mine was a used 2006 Honda Civic. The maroon paint job complimented the taco grease stain in the passenger seat quite well. And since I couldn’t afford any upgrades, I was stuck with a busted A/C and windshield wipers that seemed to work more like sandpaper than they did water repellant.
Although she wasn’t glamorous, she did her job – which was getting me to and from school safely. That was my mother’s biggest concern at the time. Not how cool I looked doing it, unfortunately.
But I’m glad she was concerned because a few years later my car ended up totaled on the westbound side of I-20. I was okay, thankfully, but my car was smashed.
No, not a drunk driver. Not a texter. It was in fact a stoned driver. Some guy behind me didn’t notice that the flow of traffic had slowed and ended up slamming right into my bumper, causing a pretty big wreck.
The sad part is no one believes me when I tell this story. People roll their eyes when I say I got hit by a driver under the influence of marijuana, not thinking it’s possible that pot can impair your ability to operate a vehicle. And that baffles me.
“So, he wasn’t drunk?” they say, truly believing that only drunk drivers cause accidents.
“Nope, just high,” I reply and roll my eyes.
To them, marijuana is harmless. Thinking that marijuana might negatively impact your health is blasphemy to them. It’s God’s medicine for Christ’s sake! No one’s ever died from it so what’s the harm, right?
But that couldn’t be further from the truth.
Smoking while driving is, in fact, dangerous. Whether you like it or not, drivers who have recently used marijuana do get into car accidents and their motor functions are distorted compared to sober reference groups.
I’m happy to argue the degree to which marijuana impairs your ability to drive a car. And I’d love to discuss its effects relative to alcohol because their effects on motor function are unique. However, that’s a different argument.
But saying marijuana has zero effects on your driving performance is just flat out wrong. And frankly, it’s kind of naïve.
In the following article I will discuss how common driving under the influence of cannabis is, the role it plays in car accidents, as well as how it specifically impacts driving performance for things like speed, reaction time, and swerving.
How Common Is Driving Under The Influence of Cannabis?
Currently, marijuana is one of the most commonly used illicit substances in the U.S., and based on recent numbers, its popularity is only rising. More states than ever are granting medical marijuana cards to users, and some are on the path to outright legalization. Yet, as more people are gaining access to marijuana, more people are hitting the roads and possibly endangering the lives of other drivers.
Recent data suggests that fewer people are driving after drinking thanks to widespread education and the creation of services like Uber and Lyft. Unfortunately, the same can’t be said for marijuana.
According to a survey of high school seniors, more students are driving after smoking marijuana than they are after drinking alcohol. And with questions about the potency of newer strains, this statistic is frightening for road travelers.
Just look at the stats…
For instance, the prevalence of driving under the influence of cannabis (DUIC) is highest in younger people (e.g. aged 16-25) and those who tend to drive at nighttime on the weekend. But don’t think this behavior is limited to those who illegally use the substance. More than half of medical cannabis patients drive while feeling a “little high,” or within 2 hours of use.
And since there is no standard recommended dose for medical marijuana, sober drivers are often at the mercy of stoned drivers to make the right decision about their ability to operate a motor vehicle.
Fortunately, data suggests that medical cannabis users who experience high levels of chronic pain tend not to drive as frequently as those who experience only moderate levels of pain. The reason why is still unclear because pain itself is still related to poor driving performance.
But how common is it for people testing positive for THC to be involved in car accidents? And what do these numbers mean?
In Washington, the amount of people involved in fatal crashes who tested positive for marijuana more than doubled since it legalized recreational use. And in states like Colorado and Oregon, crash rates increased by 6% since legalization back in 2012.
Yet, according to Johannes Ramaekers and Gunter Berghaus, this correlation doesn’t mean causation. Cannabis could just be overrepresented in these pro-legalization populations and doesn’t necessarily indicate that THC is at fault. In order to find out whether drivers who smoke marijuana are truly responsible for car accidents, one must conduct a culpability study.
Are Marijuana Users Truly At Fault for Car Accidents?
If you want to know this answer, you need to know about culpability studies. They’re important because they help assign blame to drivers and conclude whether or not substances like marijuana are at fault.
For instance, if you’re high and get rear ended by someone speeding around the corner are you responsible for that accident? Pro-marijuana advocates say no, and frankly, they’re right. Although I’d argue that they’re being reckless, we can’t blame marijuana for causing that accident.
Yet, accountability goes both ways. If someone fails to yield to another car because they recently smoked pot and are too distracted to follow road signs, then unfortunately yes, they are 100% at fault. And marijuana is to blame for that accident.
Well, researchers took note of this concept and decided to see if those testing positive for marijuana were truly responsible for increased crash rates in states like Colorado.
Initial studies done in the late 1990s and early 2000s suggested that cannabis alone didn’t increase crash culpability. In other words, they determined that marijuana users didn’t cause a spike in car accidents as predicted. Unfortunately, the issue with these studies was that they identified cannabis use among drivers by measuring THC-COOH levels instead of THC.
For those who didn’t major in Chemistry…
When you smoke marijuana, THC is converted into THC-COOH, which is then excreted through your sweat, urine, or other metabolic processes. And it’s this inactive metabolite (aka THC-COOH) that the majority of urine drug screens test for.
The issue with this approach is that THC-COOH can last in your system for weeks or months at a time. And as any avid smoker will point out, the presence of this metabolite doesn’t necessarily imply that you’ve smoked recently or that you were driving impaired. It could simply mean that you smoked once a couple weeks ago, and the drug is still floating around in your system.
But modern-day scientists aren’t concerned with whether you smoked a couple weeks ago. They’re only interested in studying the effects of drivers who are high right now (i.e. smoked within the past two hours). To do so, they needed to look at active THC levels in drivers in order to see if there’s any relationship between smoking pot and vehicular accidents.
And luckily, we have that data.
Source: Ramaekers, J G et al. “Dose related risk of motor vehicle crashes after cannabis use.” Drug and alcohol dependence vol. 73,2 (2004): 109-19. doi:10.1016/j.drugalcdep.2003.10.008
In those culpability studies, drivers with elevated THC levels in their system have increased crash culpability. That means people who smoked within the past hour or two were more likely to be responsible for traffic accidents than the sober reference group. What’s also interesting is that the more users smoked – in other words the higher their THC levels – the higher their Odds Ratio (OR) of causing an accident.
Stick with me! I’ll explain.
A drug free user has an OR of 1.0, whereas smokers with more than 2 ng/ml of THC in their system had ORs ranging from 1.74 and up to 6.6. And that’s a huge difference! This, too, is confirmed in another study by Dr. J. G. Ramaekers, in which participants who drove after smoking marijuana at least 6 times per month were more than 2.4x more likely to be involved in some form of traffic accident.
Other surveys say that number is too low, and more realistically, it’s around 3 to 7x more likely to occur.
Now, before you cry wolf, these studies did take into account the effect of alcohol and controlled for it in their approach. Interestingly enough, although alcohol alone results in a higher crash culpability ratio when compared with marijuana, the effect of combining the two is much worse.
Basically, when users combine both marijuana and alcohol, they have the highest risk of getting into a car accident based on the data. This shows that marijuana enhances the negative effects of alcohol, causing drivers to be more reckless than they would have been if they just drove drunk.
Let’s be clear about the comparison between alcohol and marijuana though as this is one of the pillars that pro-marijuana advocates often harp on. Cannabis use is associated with less severe traffic accidents (e.g. minor injuries, light vehicle damage, etc.) rather than deaths or serious injuries often seen at the hands of drunk drivers. So, no, the two substances don’t have similar consequences.
However, cannabis use isn’t free from guilt because it is directly associated with an increase in the risk of traffic crashes. That’s undeniable. And we came to that conclusion thanks to a plethora of in-depth meta-analyses over the past decade.
So, to be clear, if you smoke pot and step into a car within several hours of ingesting it, you are increasing the chances that you will cause a traffic accident.
And notice the words I used. You are increasing the chances of causing an accident, not just innocently being involved in one. And if your insurance company finds out that marijuana was to blame for the accident or that you smoked within the past several hours, you could be looking at a hefty bill or even jail time.
But heck, don’t take my word for it. Look at what the World Health Organization (WHO) published after a convention with the Expert Working Group on the Health Effects of Cannabis Use:
“There is sufficient consistency and coherence in the evidence from experimental studies and studies of cannabinoid levels among accident victims to conclude that there is an increased risk of motor vehicle accidents among persons who drive when intoxicated with cannabis.”
Marijuana Improves Driving Performance in Some Areas, but Harms it in a Majority of Others
Experimental and epidemiological research conducted over the years suggests that marijuana and driver impairment is dose related. In other words, studies show that the more you smoke, the worse your performance is behind the wheel.
The biggest concern with marijuana is that it increases something called standard deviation of lateral position (SDLP). This is scientific jargon for “weaving” or “swerving.”
SDLP is different from other metrics like driving distance and speed since it is classified as an automative behavior, and thus, operates outside of your brain’s conscious control. Because of this, it is more susceptible to the effects of drugs and alcohol and is something that the National Transportation Safety Board (NTSB) takes very seriously.
As well, marijuana users (a) find it difficult to maintain a given speed, (b) exhibit poor emergency response behavior, and (c) take increased time to respond to changing traffic light signals. Although the severity of the cannabis-induced behavior depends on THC concentration, most studies found maximal impairment around the 20 to 40-minute mark – with side-effects lasting up to 3 hours.
Now, let’s give marijuana users credit when it’s due.
Stoned drivers are better than drunk drivers at recognizing their impairment. And because of this, they do tend to drive slower and give longer headways between cars.
But does the small increase in driving performance in some areas justify the drop-off in others? Unfortunately, not.
As rudimentary as it seems to operate a vehicle, it’s an extremely complex task that involves many regions of the brain. So, an improvement to one area doesn’t mean you’re a better overall driver. In fact, substantial decreases in speed on an interstate can be quite dangerous.
So, yes, you may be right in thinking that cannabis-intoxicated drivers are less risk-averse when it comes to some issues. But a recent report by the NHTSA suggests that cannabis users aren’t as risk-averse as you think.
In their publication, they found that drivers testing positive for THC were less likely to wear seatbelts than sober reference groups, causing them to sustain unnecessary injuries to themselves and other intoxicated passengers. So, no, cannabis users aren’t free from guilt.
Yet, it’s this mix of data that makes stoned driving a controversial issue. Additionally, tolerances to drugs, differences in smoking techniques, and different absorptions of THC all complicate the matter at hand.
But overall, the consensus is pretty clear: Marijuana makes you a worse driver. And the more you smoke, the worse you are.
In sum, it appears that cannabis use impairs some driving skills, especially the ones controlled by automatic brain function like road-tracking, at low doses. For instance, participants smoking as little as 1/3rd of a joint (e.g. 6.25mg) showed decreased driving performance. And that right there is what highway safety experts have issue with.
On the other hand, driving skills that require more conscious control like speed and overtaking attempts were not as affected at lower doses. It was only until participants smoked ample amounts of marijuana that their driving performance was hindered. Regardless, there was still a negative effect of THC on their driving ability at higher doses.
It’s this dose-impairment curve that cannot be ignored. Scientists and highway traffic organizations alike are exploring this relationship in order get a better grasp on stoned driving and to establish legal limits for the drug – something I hope we can all get behind.
Whereas you might get away with smoking a little, at some point it does become irresponsible for you to step into a car and endanger other people’s lives. And personally, I believe that if you drive stoned, you should be punished, jailed, or fined since you are endangering my life as well as others on the highway.
Frankly, I don’t really care what you do at home…
I don’t think you should smoke, but I’m not going to come to your house and stop you. But once your smoking behavior threatens my safety on the road, I start to take issue. It stops being a private matter at that time and starts becoming a public safety issue.
But whatever you do and whatever your opinion, don’t mix alcohol and marijuana. The effect of the two substances together is much worse than for either alone.
YES! Marijuana Abuse is a Real Thing
If you or a loved one is struggling with marijuana abuse, we’re here to help. In fact, studies by the National Institute of Drug Abuse show that 17% of all admissions to state-funded treatment centers were for people struggling with marijuana addiction.
We know that pro-marijuana advocates often overlook that data and may judge you in reaching out, claiming that marijuana never harmed them; therefore, it shouldn’t harm you. Unfortunately, cannabis effects everyone differently, and real people have issues with it.
For my peers with cannabis use disorder (CUD) or for those who tend to drive while under the influence of cannabis (DUIC), give us a call if you’re looking to get sober. Our Admissions Specialists can be reached by phone at (817) 993-9733 or by email at firstname.lastname@example.org.
Our program lasts a minimum of 45-days and up to 90-days depending on your medical acuity. As well, we accept the majority of commercial health insurance providers like Blue Cross Blue Shield (BCBS), Aetna, Cigna, Magellan, Ambetter, PHCS Multiplan, and HealthChoice of Oklahoma. For a free and transparent quote, give us a call or submit this insurance verification form and our team will process your inquiry!
We have helped people who struggle with marijuana dependence and are happy to help you as well. For men, we offer Stonegate Center Creekside, a drug and alcohol addiction treatment center just west of Fort Worth, Texas. And for our women, we offer Stonegate Center Hilltop, a brand new treatment facility for substance use disorders in Azle, Texas.
We look forward to having you on campus and getting you back on track in your sobriety.
John Eckelbarger is a Business Development Representative for Stonegate Center. With a BSA in Chemistry from the University of Texas at Austin, he has an interest in the neurobiology of addiction & pharmacology of drugs. He hopes to bolster Stonegate Center to the forefront of addiction medicine through bold, innovative content. He is currently pursuing his MBA in Finance from Texas Christian University.