Cannabis Effects on Driving Performance

(ADCUF Trial)

Overseen By Gina Stoduto

Age: 18 - 65

Sex: Any

Trial Phase: Academic

Sponsor: Centre for Addiction and Mental Health

Must not be taking: Sedatives, Psychoactive drugs, Antihypertensives

Disqualifiers: Therapeutic cannabis, Psychiatric conditions, Substance use disorder, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Compensation: Varies

Number of Visits: 2

128 Participants Needed

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial aims to explore how cannabis affects driving performance using a simulator. Researchers will compare young drivers (ages 19-25) with middle-aged drivers (ages 35-45) and examine whether occasional versus frequent cannabis use influences results. Participants will test drive after smoking either a placebo or active cannabis (also known as marijuana or Cannabis sativa). Individuals who have used cannabis at least once in the past six months, primarily for recreation, may be suitable candidates. As an unphased trial, this study allows participants to contribute to important research on cannabis use and driving safety.

Will I have to stop taking my current medications?

The trial requires participants to stop using any drugs not prescribed for medical purposes for 48 hours before practice and test sessions. If you are a regular user of medications that affect brain function, you may not be eligible to participate.

What prior data suggests that cannabis is safe for use in driving simulations?

Research shows that cannabis use can increase the risk of car accidents, especially immediately after use. THC, the main ingredient in cannabis, causes most of its mind-altering effects. This can impair focus and reaction time, both crucial for safe driving.

Some studies found that frequent cannabis users had no driving problems after a two-day break from cannabis. However, effects can vary based on usage frequency and THC content. In this study, participants will smoke cannabis with about 15% THC, considered a strong dose.

This study uses both a placebo (a fake treatment) and real cannabis to compare effects. Similar studies have not shown clear evidence of serious safety concerns, but cannabis can affect individuals differently. Prospective participants should consider their own health and driving habits before joining the trial. ^{1 2 3 4 5}

Why are researchers excited about this trial?

Researchers are excited about this trial because it aims to understand how cannabis affects driving performance, which is crucial for public safety. Unlike traditional intoxicants like alcohol, cannabis has a different impact on motor skills and cognitive function, which this study seeks to explore in depth. By comparing the effects of a placebo and an active cannabis cigarette with 15% THC, researchers hope to pinpoint specific impairments linked to cannabis use. This knowledge could lead to better guidelines and policies for cannabis consumption and driving, ultimately enhancing road safety.

What evidence suggests that cannabis affects driving performance?

This trial will assess the effects of cannabis on driving performance. Participants will complete two sessions: one involving a simulator drive before and after smoking a placebo cannabis cigarette, and another involving a simulator drive before and after smoking an active cannabis cigarette. Research has shown that cannabis use can seriously impair driving ability. Regular users might not appear as impaired as occasional users, but both groups still experience impairment. Studies have found that cannabis can slow reaction times, increase accident risk, and worsen overall driving skills. Mixing cannabis with even small amounts of alcohol significantly worsens the negative impact on driving. Young drivers are especially affected by these impairments. ^{6 7 8 9 10}

Who Is on the Research Team?

Christine Wickens, PhD

Principal Investigator

Centre for Addiction and Mental Health

Are You a Good Fit for This Trial?

This trial is for occasional or frequent cannabis users aged 19-25 or 35-45 with a valid driver's license. Participants must not use alcohol or drugs other than prescribed ones before sessions and live in the Toronto area. Pregnant women, those with certain health conditions, and regular users of brain-affecting meds cannot join.

Inclusion Criteria

I use smoked cannabis recreationally, up to 2 times a week or 5+ times but not every day.

Willing to abstain from all other drugs not prescribed for medical purposes for the duration of the study

I have had a full driver's license for at least 12 months.

Exclusion Criteria

I am not pregnant or breastfeeding.

I have a mental health condition that makes cannabis use unsafe for me.

Urine toxicology screens negative for cannabis upon Eligibility Assessment

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Test Sessions

Participants attend two test sessions where they drive a simulator before and after smoking a cannabis or placebo cigarette. Blood samples and cognitive tasks are conducted.

2 sessions

2 visits (in-person)

Follow-up

Participants are monitored for safety and effectiveness after the test sessions, including cognitive and physiological assessments.

4 weeks

What Are the Treatments Tested in This Trial?

Interventions

• Cannabis
• Placebos

Trial Overview

The study examines how cannabis affects simulated driving performance in young versus middle-aged drivers. It compares the effects between occasional and frequent cannabis users using placebos as controls to understand age-related differences in impairment.

How Is the Trial Designed?

Group I: Age group 35 to 45 Experimental Treatment 2 Interventions

Participants will complete two sessions: one where they drive the simulator before and after smoking a placebo cannabis cigarette (\<1% THC), the other where they drive the simulator before and after smoking an active cannabis cigarette (15% ± 5% THC).

Group II: Age group 19 to 25 Experimental Treatment 2 Interventions

Participants will complete two sessions: one where they drive the simulator before and after smoking a placebo cannabis cigarette (\<1% THC), the other where they drive the simulator before and after smoking an active cannabis cigarette (15% ± 5% THC).

Who Is Running the Clinical Trial?

Centre for Addiction and Mental Health

Lead Sponsor

Trials

388

Recruited

84,200+

Published Research Related to This Trial

Vaporized THC-dominant and THC/CBD-equivalent cannabis significantly impaired driving performance, as indicated by increased lane weaving (measured by standard deviation of lateral position) compared to placebo, particularly 40 to 100 minutes after consumption.

CBD-dominant cannabis did not show significant impairment compared to placebo, suggesting it may not affect driving ability; however, the study notes that the tested doses may not reflect typical usage patterns.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effect of Cannabidiol and Δ9-Tetrahydrocannabinol on Driving Performance: A Randomized Clinical Trial. Arkell, TR., Vinckenbosch, F., Kevin, RC., et al.[2021]

This study will assess the effects of both oral and vaporized cannabis on driving performance, cognitive abilities, and field sobriety in healthy adults, involving 64 participants across two double-blind, placebo-controlled trials.

By examining the impact of cannabis alone and in combination with alcohol, the research aims to enhance understanding of impairment levels, which could influence public policy and law enforcement standards regarding cannabis and alcohol use.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The effects of oral and vaporized cannabis alone, and in combination with alcohol, on driving performance using the STISIM driving simulator: A two-part, double-blind, double-dummy, placebo-controlled, randomized crossover clinical laboratory protocol. Zamarripa, CA., Novak, MD., Weerts, EM., et al.[2023]

High doses of cannabis significantly impaired driving performance more than lower doses, while alcohol had minimal effects and did not enhance impairment when combined with cannabis.

Both substances increased speed and variability in driving, but high-dose cannabis led to decreased mean speed and longer reaction times, highlighting the need for further research on their individual effects on driving safety.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The effects of cannabis and alcohol on simulated arterial driving: Influences of driving experience and task demand. Lenné, MG., Dietze, PM., Triggs, TJ., et al.[2022]

This study will assess the effects of cannabidiol (CBD) on driving performance and cognitive function in 30 healthy individuals, using a randomized, double-blind, placebo-controlled design to ensure reliable results.

The research aims to determine if CBD causes any impairment in driving, comparing its effects to a placebo, and will also investigate whether CBD could lead to false-positive drug tests for Δ9-THC, ensuring safety for drivers using CBD.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The effect of cannabidiol on simulated car driving performance: A randomised, double-blind, placebo-controlled, crossover, dose-ranging clinical trial protocol. McCartney, D., Benson, MJ., Suraev, AS., et al.[2021]

Acute use of tetrahydrocannabinol (THC) significantly impairs certain driving abilities, although the effects are generally modest, as shown by simulator and road course studies.

Factors such as dose, delivery method, and individual tolerance influence the level of impairment, while the role of cannabidiol in mitigating THC-induced impairment remains unclear and requires further research.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Cannabis and driving ability. Sevigny, EL.[2022]

In a study with 14 healthy volunteers, both THC-dominant and THC/CBD equivalent cannabis impaired driving performance, particularly increasing lane weaving, indicating that both types can negatively affect driving safety.

Interestingly, the THC/CBD equivalent cannabis led to higher peak plasma THC levels and caused greater impairment on certain cognitive tasks compared to THC-dominant cannabis, suggesting that CBD may not mitigate THC's adverse effects and could potentially worsen them.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Cannabidiol (CBD) content in vaporized cannabis does not prevent tetrahydrocannabinol (THC)-induced impairment of driving and cognition. Arkell, TR., Lintzeris, N., Kevin, RC., et al.[2022]

Medical marijuana can impair driving performance and increase the risk of motor vehicle collisions, similar to other medications that affect psychomotor function, highlighting the need for healthcare providers to inform patients about these risks before prescribing it.

Patients using medical marijuana should avoid driving for at least 8 hours after feeling a 'high' and be cautious of the combined effects with alcohol and other psychoactive substances, emphasizing the importance of public safety in the context of increasing medical marijuana use.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Medical marijuana and driving: a review. Neavyn, MJ., Blohm, E., Babu, KM., et al.[2022]

In a study involving 74 healthy adult volunteers, vaporization of low-THC, CBD-rich cannabis products did not significantly impair driving-related abilities compared to a placebo, suggesting that these products may be safe for driving.

THC levels in the blood peaked shortly after consumption but dropped below detectable levels within 1.5 hours for most participants, although some still had detectable THC up to 5 hours later, which could have legal implications for drivers.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effect of vaporizing cannabis rich in cannabidiol on cannabinoid levels in blood and on driving ability - a randomized clinical trial. Egloff, L., Frei, P., Gerlach, K., et al.[2023]

Cannabis use has significantly increased over the past 15 years, and it is the most commonly detected substance in drivers suspected of drug impairment, highlighting a public safety concern.

Experimental studies confirm that cannabis impairs psychomotor performance, especially at high doses or when combined with alcohol, necessitating better models to interpret blood cannabinoid levels in relation to driving impairment.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

[Cannabis and automobile driving]. Ménétrey, A., Augsburger, M., Giroud, C., et al.[2008]

A study using a driving simulator and real driving conditions found that THC significantly impairs driving performance, causing increased drowsiness and instability in vehicle control.

The driving simulator was more sensitive in detecting THC's effects on driving, suggesting it can effectively predict driving safety after drug use.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Cannabis smoking impairs driving performance on the simulator and real driving: a randomized, double-blind, placebo-controlled, crossover trial. Micallef, J., Dupouey, J., Jouve, E., et al.[2019]

Citations

1.

pmc.ncbi.nlm.nih.gov

pmc.ncbi.nlm.nih.gov/articles/PMC3836260/

Cannabis Effects on Driving Skills - PMC - PubMed Central

Drivers claiming regular cannabis consumption (177 of 456) were significantly less often (32% vs 55%) to be judged as impaired by CTI than occasional smokers, ...

2.

pmc.ncbi.nlm.nih.gov

pmc.ncbi.nlm.nih.gov/articles/PMC9949874/

The Effects of Cannabidiol on the Driving Performance ...

CBD may cause drowsiness and slight detriments to driving performance, including more collisions, slower brake reaction times, and slightly higher lateral ...

3.

sciencedirect.com

sciencedirect.com/science/article/pii/S1369847824002043

Attitudes toward driving after cannabis use: A systematic ...

Attitudes toward driving after cannabis use are predominantly unfavorable. There is variability in attitudes towards driving after cannabis use across studies.

4.

ccsa.ca

ccsa.ca/sites/default/files/2022-12/CCSA-Cannabis-Use-Driving-Report-2022-en.pdf

Cannabis Use and Driving

Combining cannabis with even small amounts of alcohol greatly increased the negative effects on driving skills. (Downey et al., 2013; Hartman et al., 2015 ...

5.

clinicaltrials.gov

clinicaltrials.gov/study/NCT01592409?term=AREA%5BConditionSearch%5D(%22Psychomotor%20Disorders%22)&rank=8

Cannabis Effects on Driving-related Skills of Young Drivers

This study will test the prediction that residual effects of an acute dose of cannabis on driving-related skills will be observed in a group of young drivers 48 ...

6.

pmc.ncbi.nlm.nih.gov

pmc.ncbi.nlm.nih.gov/articles/PMC9940647/

Cannabis Effects on Driving Performance

Although several studies have concluded there is moderate increased crash risk associated with acute cannabis use, few studies have explored the ...

7.

cdc.gov

cdc.gov/cannabis/health-effects/driving.html

Cannabis and Driving

If you intend to drive, the safest option is not to use any alcohol or drugs, including cannabis. Here are steps you can take to help prevent ...

8.

aaafoundation.org

aaafoundation.org/wp-content/uploads/2024/12/202412-AAAFTS-Cannabis-Fact-Sheet-Traffic-Safety.pdf

202412_Cannabis Fact Sheet_Traffic Safety

Overall, THC is accepted as responsible for the intoxicating effects of cannabis, while there is little or no evidence that CBD impairs driving (Arkell et al., ...

9.

today.ucsd.edu

today.ucsd.edu/story/frequent-cannabis-users-show-no-driving-impairment-after-two-day-break

Frequent Cannabis Users Show No Driving Impairment After ...

After at least 48 hours of abstinence, frequent cannabis users showed no impartments in driving performance in a driving simulator study ...

10.

jamanetwork.com

jamanetwork.com/journals/jamapsychiatry/fullarticle/2788264

Driving Performance and Cannabis Users' Perception of ...

This randomized clinical trial studies the magnitude and time course of effects of cannabis on driving, effect of cannabis with different.