Cannabidiol in the context of first-time road traffic medical fitness testing in Switzerland: Retrospective study on the significance and influence on the assessment outcome

Abstract

Background: In addition to tetrahydrocannabinol (THC), cannabidiol (CBD) is an important component of cannabis plants (C. sativa and C. indica). While CBD itself has not been shown to cause important psychoactive effects and is not listed as a narcotic, clinical trials have proven sedative and relaxing effects. Since 2014 tobacco substitute products containing CBD and <1% THC are legally sold in Switzerland. Objective: It is unclear if, and at which concentration CBD has an effect on the (short-term) fitness to drive. More importantly, consumption of tobacco substitute products with a THC content <1% can cause the level of THC in blood to exceed the existing legal limit for driving (in Switzerland 1.5 µg/L), which is automatically classified as driving under the influence of drugs (DUID). This study examined the role of CBD in obligatory traffic medicine examinations after a first-time cannabis DUID. Methods: A retrospective keyword-based search and analysis of the database of the department for traffic medicine at the Institute for Legal Medicine of the University of Zurich were carried out. A descriptive statistical analysis of the results. Inclusion criteria: closed traffic medicine case after first time DUID (cannabis) with exclusion of any other narcotic substances. The investigation covered the time period 1 January 2016–31 December 2019. The analysis also included age, sex and the legal verdict. Results: In the period analyzed there were a total of 62,997 cases, 1082 of which were first-time DUID under cannabinoids. No cases prior to 1 January 2016 but then a continual increase up to 15.17% of all cannabis reports in 2019. (Co)consumption of CBD: 62 cases (5.7%). Most consumers were male (91.9%). Different age distribution between consumers of CBD and THC with a conspicuous accumulation in subjects 30–40 years old. Very small differences in the assessment of driving ability. Conclusion: In this sample set CBD played a minor but increasing role in determining the outcome of assessments after a first-time DUID (cannabis). Therefore, an influence of CBD on the fitness to drive cannot be deduced. As there are also no other published data on this issue, the authors are of the opinion that there is a need for clinical prospective research projects to clarify the effect of CBD on the subjective perception of the fitness to drive and deficits in the ability to drive.