A study into the ‘next day’ performance of people given an oil containing THC and CBD has found that cannabis has no significant impact on safety-sensitive tasks such as driving a vehicle.
Cannabis, specifically the THC contained within, is well known to produce an effect on cognitive function in the period following consumption, but, some patients fear this will restrict their ability to drive or operate machinery the morning after use.
In a study published in the journal Psychopharmacology, researchers examined data produced by a study that examined the effects of TNC and CBD on insomnia disorder.
Participants in the New Zealand-based study were all light or very light users of cannabis, “Most participants (75%) were either cannabis-naïve or had < 10-lifetime exposures to cannabis while 5 participants (25%) had > 10-lifetime exposures. None had used cannabis or cannabinoid products in the last three months; as confirmed by a urinary drug screen.”
The cohort was asked to attend two 24-hour sessions with researchers who administered a currently available medical cannabis oil, or a placebo, to the participants who had previously been diagnosed with insomnia.
The 20:1 (200mg CBD and 10mg THC) cannabis oil product, or the placebo was given to participants in the evening, the following morning they partook in a series of cognitive and psychomotor function tasks, including a simulated driving session.
Participants underwent tests within 2 hours of waking, these included, “Digit Symbol Substitution Task (attention, working memory, and visuospatial function), Divided Attention Task (working memory), Paced Serial Addition Task (working memory, attention, and simple arithmetic problem-solving), Word Pairs Task (declarative memory), Finger Tapping Task (procedural memory), Stroop Test (executive function), and N-Back Task (working memory and information processing)”
Driving performance was measured 10 hours after administration of cannabis or placebo by a simulator designed specifically to assess drivers who use THC, “… using a fixed-base driving simulator (Hyperdrive, Adelaide, Australia) equipped with standard vehicle controls and a custom-built 30-minute scenario that has previously demonstrated sensitivity to the acute effects of THC in healthy volunteers” the study author’s explained.
The results showed “no significant” differences in test outcomes between those in the placebo group and those who had been administered the 20:1 cannabis oil. The one test the data showed to be different was the Stroop Test, which examines executive function.
Driving simulator results were consistent with the cognitive test results in that they showed no significant differences between the two groups.
“There was a small reduction in percentage accuracy on the Stoop-Colour test for THC/CBD relative to placebo. No other significant differences were observed for any of the cognitive performance tasks.” wrote the researchers.
Outcome measures for the simulated driving task are presented in Table 3. None of the simulated driving outcome measures were significantly different between THC/CBD and placebo.” the study authors wrote.
In their conclusion, the authors advise that more research is required, but seem confident in stating that a single dose of cannabis oil in the evening does not impair safety-sensitive tasks the following morning.
”The use of cannabis by night as a sleep aid is highly prevalent and there are legitimate concerns that this may lead to impaired daytime (‘next day’) function, particularly on safety-sensitive tasks such as driving. The results of this study indicate that a single oral dose of 10 mg THC (in combination with 200 mg CBD) does not notably impair ‘next day’ cognitive function or driving performance relative to placebo in adults with insomnia disorder who infrequently use cannabis. Larger studies in patient populations are required to determine the effects of repeated dosing with THC (with or without CBD), and at higher doses of THC, on ‘next day’ function.”
