[WARNING] The legal DUI deadlier than drunk driving

As a former forensic pathologist and Florida State Medical Examiner, I know that the vast majority of drunk drivers involved in automobile accidents consumed way beyond the proverbial “one too many.” Very often they had 10 to 12 drinks too many. 

And since 1954, law enforcement officers have had a test—called a breathalyzer—to estimate alcohol intoxication and to help keep our roadways safe.  

By comparison, new research shows that even just a very small dose of marijuana significantly impairs driving ability. Yet, we still don’t have a test to measure marijuana intoxication, even though many states have already legalized use of the drug. 

Let’s take a closer look at why this is such a big problem 

Researchers study effects of cannabis on driving ability 

Researchers in The Netherlands recently studied the effects of marijuana on driving ability in 26 healthy volunteers who had occasionally used the drug in the past.  

The researchers designed the study as a within-participant cross-over trial, which means that each participant acted as their own control. And they divided the study into four phaseswhere the participants would take four separate driving tests after inhaling four different substances via vape pen:  

  • Test 1: Placebo 
  • Test 2: 13.75 mg of tetrahydrocannabinol (THC) 
  • Test 3: 13.75 mg cannabidiol (CBD) 
  • Test 4: 13.75 mg 50:50 of THC and CBD 

THC and CBD are two active compounds found in Cannabis(marijuana) plants. However, they act very differently in the body…  

THC is the major, psychoactive chemical that produces the “high” sensation. On the other hand, CBD activates different cannabinoid receptors in the brain and doesn’t produce the “high” sensation, even though it’s also psychoactive. (This helps explain why some people report improvements in anxiety and depression when using CBD alone.)  

The researchers also included the 50:50 administration of THC and CBD to test some claims that CBD may somehow decrease the effects of THC. 

Well, here’s what they found… 

Road hazard at very low doses 

After administering each test, the participants drove 100 kilometers (km) on real roadways around Maastricht in The Netherlands(There was also an instructor in the car with an independent set of controls if it got too dangerous.)  

Specifically, for the driving test, the researchers looked at something called standard deviation of lateral position (SDLP)—which measures how much the driver swerves. A camera mounted on top of the car measured how the car deviated from the center and outside lines, every four seconds.  

From past experiments, we know that sober people given a placebo typically keep about 50 cm (20 inches) away from the lines when driving. And people with a blood alcohol content of 0.05 percent (which is under the legal limit of 0.08 in most U.S. states) have a SDLP of about 2.4 cm (or about 5 percent higher than sober drivers). 

When the participants in this study took their driving tests, here’s what happened in the first 100 minutes: 

  • CBD alone didn’t cause much swerving compared to placebo. 
  • THC alone caused increased swerving by 2.3 cm over placebo (which is about the same as having a blood alcohol level of 0.05). 
  • THC plus CBD caused the most swerving (2.8 cm) compared to placebo. 

So, clearly, CBD alone doesn’t cause much intoxication…whereas THC does. Andunlike what some had theorizedTHC plus CBD impaired driving ability the most! In fact, it impaired driving more than what occurs when an average-sized man has about two drinks in an hour.  

Plus, I’m sure the effects of smoking marijuana are actually much worse when people do it in the real-world. Here’s why…  

Since participants were driving on real public roads, the researchers intentionally administered very small doses of THC (just 13.75 mg). But a typical marijuana cigarette (a “joint”) contains about 10 times more THC than that measly amount! 

By this standard, the typical marijuana joint is 10 times more intoxicating than alcohol when it comes to operating an automobile.  

Plus, this study only analyzed swerving while driving. But swerving isnt the only result of marijuana intoxication. It can also cause impairments in judgment, visual perception, response time, wakefulness, and much more. Which helps explain why states that have legalized marijuana have seen a 200 percent increase in DUI accidents and fatalities. And why drugged driving” now surpasses drunk driving! 

So, it boggles the mind (like marijuana itself) that politically correct politicians keep ratcheting down blood alcohol limits to ridiculously low levels. Yet, meanwhile, they push to further expand the acceptance of marijuanawhich clearly already poses a far greater threat to the safety of our roads in reality. 

Find safer ways to reduce stress and pain  

On top of all thattheres been a huge uptick in marijuana use since the beginning of the coronavirus pandemic. And that increase relates directly to the nationwide lockdowns that limited or cut off access to safe, effective, non-drug approaches to deal with stress, anxiety, and pain. All in the midst of a very real opioid drug epidemic. 

As always, I urge you to find ways to improve your mood, ease anxiety, and reduce painwithout resorting to marijuana or any other harmful drug. Instead, I suggest trying out some relaxing, mind-body approaches—such as acupuncture, bodywork, massage, and yoga—that support your overall well-being. (See my books Your Emotional Type and Overcoming Acute and Chronic Pain: Keys to Treatment Based on Your Emotional Type for more about using these approaches that will work best for you personally). 

Lastly, if you reside in, or near, one of many states where they now have legalized marijuana, be extra wary. Not all roads are as straight and flat as in The Netherlands! 


“Effect of Cannabidiol and Δ9-Tetrahydrocannabinol on Driving Performance: A Randomized Clinical Trial.” JAMA, 2020;324(21):2177–2186. doi:10.1001/jama.2020.21218