Any substance that alters one’s mental states raises concerns over the safety of using said substance behind the wheel. Can CBD or THC — two active ingredients found in marijuana — impair your ability to drive, and increase the likelihood of accidents? Many studies have examined this problem, including a recent 2019 study, which looked specifically into how the combination of CBD and THC affects drivers.

The basics of these two substances

Both THC and CBD are found in cannabis plants. However, the two have very different effects on your body.

THC is a natural stimulant that leaves you feeling intoxicated and may cloud your senses and your judgments. Its effects vary depending on the user and on the concentration utilized, but THC may heighten your senses, distort your sense of time, reduce your motor skills, reduce your inhibitions, and make it harder for you to focus.

CBD, on the other hand, is generally understood to be a non-intoxicating substance. It’s a downer which brings about feelings of calm and relaxation. It also contains anti-inflammatory and analgesic properties, which make it valuable in the treatment of several conditions, including cancer pain, arthritis, and some skin conditions.

Both substances are sold in isolation in the form of CBD oil, cannabis oil, CBD isolates, and THC isolates. They may also be found as part of many products, including edibles and vaping liquids. However, those smoking marijuana will often take in both cannabinoids at once, which raises concerns over how the combination may affect your driving skills. Especially for those who use medical marijuana as part of an ongoing treatment.

The details of the study

The literature on THC and driving is quite clear. The substance leaves drivers intoxicating and impairs their abilities to drive by a significant amount. Being stoned is still overall safer than being drunk, but neither is ideal when behind the wheel. It’s for good reason that many countries make it illegal to drive after smoking marijuana. At least 18 US states have zero-tolerance laws against the use of marijuana behind the wheel.

What interested researchers of this study, however, was understanding whether a higher concentration of CBD could make it safer to drive under the influence of THC. It has long been speculated that CBD may help mitigate the negative effects of THC, which is true in some cases. As a natural anxiolytic, CBD helps prevent many negative effects of THC, including helping cut back on the paranoia that may be induced by the substance.

The methodology of the study was simple. Participants took part in simulated driving exercises after being dosed with 125 mg of three different mixtures:

1 – A THC-dominant mixture, containing 11% THC and less 1% CBD;

2 – A THC/CBD equivalent mixture, containing 11% THC and 11% CBD;

3 – A placebo, containing less than 1% of both CBD and THC.

The result was that CBD appears to have no impact on one’s ability to drive under the influence of THC. To make matters worse, the researchers found that “peak plasma THC concentrations were higher following THC/CBD equivalent cannabis relative to THC-dominant cannabis.” It appears that, for unclear reasons, mixing CBD and THC increases the amount of THC that  participant’s bloodstream.

If you are a medical marijuana user who’s been driving under the influence because it’s legal where you live, this study is worth reading in full. While THC does impair your ability to drive, researchers pointed out that the impact is minimal. It may only become apparent if you are required to perform complex driving tasks.

As for the effects of CBD alone in relation to your ability to drive, the researchers noted that they did not look into it because “vaporization of CBD alone is uncommon in the real world and because acute administration of CBD in previous human laboratory studies has not produced notable drug effects that are suggestive of intoxication or impairment.” If you haven’t tried CBD yourself, this Cibdol guide will help you understand the substance a little better.


Arkell, T.R., Lintzeris, N., Kevin, R.C. et al. Cannabidiol (CBD) content in vaporized cannabis does not prevent tetrahydrocannabinol (THC)-induced impairment of driving and cognition. Psychopharmacology 236, 2713–2724 (2019).