In a recent dutch experiment, researchers showed that inhaling vaporized cannabis containing much more cannabidiol than Δ9-tetrahydrocannabinol does not affect driving performance more than inhaling a placebo.
Cannabis consists of chemical substances called cannabinoids, two of which are well known and studied: tetrahydrocannabinol or THC, the psychotropic substance of cannabis, used in recreational use, and cannabidiol or CBD, used in the treatment of anxiety, psychosis, epilepsy, and neurological disorders. An experiment to determine the different effects of CBD and THC was conducted by researchers from the Maastricht University School of Psychology and Neuroscience in the Netherlands, where the use of cannabis is legal.
Why such an experiment?
Epidemiological studies have found serious links between cannabis use and an increase in traffic accidents. An important effect is indeed the increase of the SDLP (a measure of lane weaving, swerving, and overcorrecting), which measures the deviation and overcorrection when driving on a road. This measuring instrument has been validated and is used in particular for driving disorders associated with alcohol and other drugs.
In analyzing the literature, the researchers found that the different effects of the two substances on cognitive and psychomotor abilities were not very clear, although CDB still appeared harmless for these variables, unlike its counterpart, THC. So they wanted to be sure and set up an experiment to answer their questions.
The researchers behind this study examined the influence of CDB on the intensity and duration of the impairment of driving behavior caused by cannabis vaping, by varying the amount of the two main active substances THC and CDB. They conducted a randomized, double-blind, placebo-controlled cross-experiment among 26 healthy, occasional cannabis users. The participants used cannabis consisting mainly of THC, CBD, THC/CBD equivalent, or a placebo of cannabis containing neither. The goal of the experiment is to test the effects of cannabis on SLDP.
Before each test, all participants alternately inhaled THC-dominant, CBD-dominant, THC/CBD-equivalent cannabis, and placebo cannabis. The driving evaluation consisted of driving 100 km at a constant speed on a circuit for 40 minutes and four hours after inhaling cannabis or synthetic cannabinoids.
CBD does not affect driving more than a placebo
The results showed that inhaling THC-dominant cannabis and THC/CBD-equivalent cannabis permanently alters the SDLP (a measure of lane weaving, swerving, and overcorrecting) compared to placebo cannabis. On the other hand, using CBD-dominant cannabis has no more effect on SDLP than placebo cannabis. In their analysis, the researchers also measured other parameters suggesting that the subjective feeling of driving quality is significantly impaired with THC-dominant and THC/CBD-equivalent cannabis. However, with THC/CBD-equivalent cannabis, the duration of action was much shorter. This is consistent with what is already known about the interaction between these molecules in the body, with CDB sometimes being used to accelerate the elimination of THC from the blood.
Limitations of the study
This study is innovative and its design meets the highest standards of clinical trials. However, it has some weaknesses, such as the sample size, sample composition, and doses used, which do not correspond to the doses frequently consumed in reality. Consequently, the results of the experiment are only valid for this experiment.
If extrapolation is attempted, it can only be done for occasional, healthy users and not for more regular users. Similarly, extrapolation cannot be made for other doses and other plant varieties. The participants in the study were also young. As a result, their driving experience is limited, which may have influenced the results. Finally, the design of the study was such that an effect of THC on driving behavior could be established. It cannot be ruled out that the test lacked the statistical power to detect the minimal effects of CBD use.