Cannabidiol (CBD) content in vaporized cannabis does not prevent tetrahydrocannabinol (THC)-induced impairment of driving and cognition.
Does medical cannabis differ from recreational cannabis with respect to driving?
Defining medical cannabis.
Medical cannabis can refer to a wide variety of products and methods of preparation including herbal cannabis (the dried
flowers of the cannabis plant) and cannabis extracts (e.g., oils, tinctures). In general, these products contain either THC or
CBD as the primary active ingredient, or some combination of the two compounds. There is an ever-growing number of
cannabis strains (varieties of the plant) which can vary substantially with respect to concentrations of THC, CBD, and other
plant compounds. There are also several medical products with market authorization, such as Dronabinol and Sativex® (an
oromucosal spray containing a 1:1 ratio of THC and CBD which is used to treat spasticity associated with multiple sclerosis).
An important issue in the provision of cannabis preparations for medical use is how it is consumed. Smoking is a common
route of administration (and the traditional mode of consumption for recreational consumers) because it produces a rapid
onset of drug effects. Safer and more precise methods of administration are available, however, such as vaporizing below the
point of combustion (vaping) or ingesting oils or extracts. Smoking is not recommended as a route of administration because
of its adverse health effects.
Should patients who are prescribed medical cannabis be given a medical designation for
driving?
Those who use cannabis medically should do so under the supervision of a qualified medical professional. They are advised
to titrate doses upward slowly as needed and as approved by a medical professional. They should refrain from driving in the
first two weeks after initiation of cannabis use and after each increase in dose. They should also be made aware of legislation
pertaining to medical use of cannabis in their jurisdiction.
Does CBD affect driving performance and can it counteract the effects of THC?
A recent on-road driving study showed CBD-dominant cannabis did not produce any driving impairment compared to
placebo,13 although at least one study suggested CBD might be associated with impairment.14 Further, it seems that when
consumed with alcohol, CBD can increase impairment and more research on this topic is needed. Cannabis containing mainly
THC or a combination of THC and CBD, did cause driving impairment for up to four hours after inhalation. From this and
another study,15 it can be concluded that CBD when consumed alone, does not impair driving performance nor does CBD reduce
the impairing effects of THC.
Do novel synthetic cannabinoids (SCs) pose a risk to traffic safety?
Yes, novel SCs potentially pose a serious traffic safety risk.
While some medical cannabinoids have been synthetically manufactured for decades, novel SCs represent a large group of
new psychoactive substances with 209 identified in the European Union (EU) over the 13 years between 1 January 2008
and 31 December 2020, including 11 identified for the first time in 2020.16 SCs are often sold as herbal smoking blends with
names such as Spice, K2 and Kronic. SCs bind to the same receptors as tetrahydrocannabinol (THC) but often have far higher
potency and efficacy.17 Controlled administration laboratory studies using low doses of one of the earliest SCs (JWH-018)
demonstrated acute impairment of motor coordination, attention, response speed, and memory.18,19 It is expected that effects
on psychomotor performance in consumers who use large amounts or overdose on SCs pose an even greater road safety risk
than demonstrated in these studies.