THC for Driving Performance

Overseen By Heather Barkholtz, PhD

Age: 18 - 65

Sex: Any

Trial Phase: Phase < 1

Sponsor: University of Wisconsin, Madison

Must not be taking: Mood stabilizers, sedatives

Disqualifiers: Substance use disorder, pregnancy, others

Compensation: Varies

Number of Visits: Unknown

Duration: 9 months

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial tests how different types of THC, the main active ingredient in cannabis, affect driving. Researchers aim to determine if Delta-8-THC and Delta-9-THC impact driving abilities compared to a placebo. The trial seeks to understand how these substances are processed in the body and their potential effects on driving. It suits individuals who have used cannabis in the past two years, hold a driver's license, and maintain good mental health. As an Early Phase 1 trial, this research focuses on understanding how these THC variants work in people, offering participants a chance to contribute to groundbreaking insights.

Will I have to stop taking my current medications?

The trial requires that you do not use medications that may impact driving ability, such as mood stabilizers or sedatives.

Is there any evidence suggesting that this trial's treatments are likely to be safe?

Research shows that both Delta-8-THC and Delta-9-THC can impair driving and cognitive abilities. Studies comparing these substances reveal that Delta-9-THC can impair driving skills for several hours after use, with most individuals regaining normal driving abilities about five hours later.

The effects of Delta-8-THC are less well-known. Some studies suggest it might impair driving similarly to Delta-9-THC, but more research is needed to understand its full impact. Delta-8-THC is often used in areas where marijuana is restricted, leading to use without full awareness of its effects.

Researchers are studying both substances to learn more about their safety and impact on activities like driving. Participants in these studies have reported feeling impaired, emphasizing the need for caution when using these substances, especially before driving. ^{1 2 3 4 5}

Why are researchers excited about this trial's treatments?

Researchers are excited about using Delta-8-THC and Delta-9-THC for assessing driving performance because these compounds are derived from cannabis and may affect cognitive and motor functions differently than traditional substances like alcohol or prescription medications. Unlike other substances that impair driving, Delta-8-THC and Delta-9-THC each have unique chemical structures, potentially leading to varied effects on reaction time and decision-making. This trial aims to clarify how these specific forms of THC influence driving abilities, which could inform future guidelines and safety measures for cannabis use related to driving.

What evidence suggests that this trial's treatments could be effective for driving performance?

This trial will compare the effects of Delta-8-THC and Delta-9-THC on driving performance. Research has shown that both Delta-8-THC, which participants may receive, and Delta-9-THC, another treatment option, can impair safe driving. Delta-8-THC can hinder clear thinking and quick reactions, crucial for safe driving, making it harder to respond to sudden changes on the road. Similarly, Delta-9-THC affects thinking and driving skills. Studies indicate that driving ability can be impaired for several hours after using Delta-9-THC. Both substances can reduce driving safety by slowing reaction time and affecting judgment. ^{1 6 7 8 9}

Who Is on the Research Team?

Heather Barkholtz, PhD

Principal Investigator

University of Wisconsin, Madison

Are You a Good Fit for This Trial?

This trial is for people aged 18-49 who have used cannabis in the last two years, are in good mental health, don't have major medical issues, speak English, and can drive (with a valid license and at least two years of experience).

Inclusion Criteria

Recent cannabis use (within past two years)

Good mental health as determined by self-reported responses to the Psychopathology Screener

Absence of any major medical, cardiovascular, endocrine, and neurological condition as determined by self-reported responses to the Medical History Screener

Exclusion Criteria

Any serious prior adverse response to cannabis

History of or current substance use disorder as determined by self-reported responses to the Internalizing, Externalizing, and Substance Use Disorder Screener

Pregnancy or lactation (pregnancy test, if needed)

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Treatment

Participants receive Δ9-THC and Δ8-THC isolates or placebo to evaluate pharmacokinetics and driving impairment

9 months

Follow-up

Participants are monitored for safety and effectiveness after treatment

4 weeks

What Are the Treatments Tested in This Trial?

Interventions

• Delta-8-THC
• Delta-9-THC

Trial Overview The study tests how Δ9-THC and Δ8-THC affect driving. Participants will receive either one of these cannabis compounds or a placebo to see how it impacts their driving skills using standardized dosing and impairment detection methods.

How Is the Trial Designed?

Group I: delta-9-THC Experimental Treatment 1 Intervention

Group II: delta-8-THC Experimental Treatment 1 Intervention

Group III: Placebo Placebo Group 1 Intervention

Delta-8-THC is already approved in United States for the following indications:

Approved in United States as Delta-8-THC for:

• None officially approved; widely available due to hemp legalization but lacks formal approval for specific indications

Who Is Running the Clinical Trial?

University of Wisconsin, Madison

Lead Sponsor

Trials

1,249

Recruited

3,255,000+

Published Research Related to This Trial

A study involving 21 healthy adults found that tetrahydrocannabivarin (THCV) has a favorable safety profile, with most adverse events being mild and euphoric mood being the most common side effect.

Preliminary results suggest that certain doses of THCV (specifically 12.5, 25, and 200 mg) may improve sustained attention, although the effects were not consistently dose-dependent and higher doses led to THC-like effects, which could result in positive urine drug screens.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

A Two-Phase, Dose-Ranging, Placebo-Controlled Study of the Safety and Preliminary Test of Acute Effects of Oral &#916;8-Tetrahydrocannabivarin in Healthy Participants. Peters, EN., MacNair, L., Harrison, A., et al.[2023]

A survey of delta-8-THC consumers revealed that over half (51%) use it to treat various health conditions, with anxiety and stress being the most common, suggesting potential therapeutic benefits.

Participants reported favorably comparing delta-8-THC to delta-9-THC and pharmaceutical drugs, indicating it may have similar efficacy with potentially fewer adverse effects, although knowledge about safe dosages and medical integration remains low.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Consumer Experiences with Delta-8-THC: Medical Use, Pharmaceutical Substitution, and Comparisons with Delta-9-THC. Kruger, DJ., Kruger, JS.[2023]

Delta-8-tetrahydrocannabinol (Δ8-THC) is widely available over-the-counter in the U.S. despite being classified as a Schedule I drug, leading to concerns about its legal status and safety due to unregulated sales.

The lack of regulation for Δ8-THC products has resulted in health risks, including medical emergencies from high-dose exposure, particularly in children, highlighting the urgent need for legislative action to ensure product safety and accurate labeling.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

&#916;8-THC: Legal Status, Widespread Availability, and Safety Concerns. Babalonis, S., Raup-Konsavage, WM., Akpunonu, PD., et al.[2022]

In a study involving 10 experienced marijuana smokers, oral Delta-9-tetrahydrocannabinol (Delta(9)-THC) was found to be chosen more often than a placebo, indicating some reinforcing effects, although participants selected it less than 50% of the time.

Both doses of Delta(9)-THC (10 mg and 20 mg) led to significant increases in positive subjective effects, impaired psychomotor performance, and increased heart rate, suggesting potential safety concerns alongside its therapeutic use.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Reinforcing effects of oral Delta9-THC in male marijuana smokers in a laboratory choice procedure. Hart, CL., Haney, M., Vosburg, SK., et al.[2022]

A controlled study found that both medium (16.5 mg) and high doses (45.7 mg) of THC from hemp milk significantly impaired driving skills, with participants showing marked intoxication and reduced willingness to drive after consuming the highest dose.

The study revealed that the combined blood levels of THC and its active metabolite, 11-OH-THC, provided a better estimate of driving impairment than THC alone, indicating that both compounds should be considered when assessing the effects of cannabis on driving ability.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Assessment of driving capability through the use of clinical and psychomotor tests in relation to blood cannabinoids levels following oral administration of 20 mg dronabinol or of a cannabis decoction made with 20 or 60 mg Delta9-THC. Ménétrey, A., Augsburger, M., Favrat, B., et al.[2019]

Delta(9)-tetrahydrocannabinol (Delta(9)-THC) has well-documented therapeutic benefits, including reducing nausea from chemotherapy, increasing appetite, alleviating pain, and relieving symptoms of multiple sclerosis, supported by extensive research over the past 30 years.

While Delta(9)-THC can impair cognitive functions such as memory and perception, and may induce negative psychological effects like panic and hallucinations, the long-term impacts are still unknown, leading to a proposal by WHO to reschedule it as a low-risk substance.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The good and the bad effects of (-) trans-delta-9-tetrahydrocannabinol (Delta 9-THC) on humans. Carlini, EA.[2013]

Dronabinol (medicinal THC) significantly impairs driving performance in both occasional and heavy cannabis users, with measurable increases in weaving (SDLP) and reaction time (TSA) after administration, indicating a dose-dependent effect.

Heavy users exhibited less driving impairment compared to occasional users, likely due to tolerance, while the Standard Field Sobriety Test failed to effectively identify clinically relevant impairment caused by dronabinol.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Medicinal Δ(9) -tetrahydrocannabinol (dronabinol) impairs on-the-road driving performance of occasional and heavy cannabis users but is not detected in Standard Field Sobriety Tests. Bosker, WM., Kuypers, KP., Theunissen, EL., et al.[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]

In a pilot study of 58 subjects, delta 9-THC levels in hemolyzed blood peaked shortly after smoking and stabilized within an hour, reaching levels similar to those found in impaired drivers, indicating significant impairment potential.

Subjects exhibited an 'adaptation' effect, where their self-perception of impairment did not align with their actual performance on sobriety tests, suggesting that THC's effects may persist beyond measurable blood levels due to metabolites affecting the central nervous system.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Hemolyzed blood and serum levels of delta 9-THC: effects on the performance of roadside sobriety tests. Reeve, VC., Robertson, WB., Grant, J., et al.[2013]

A standardized dose of CannEpil, a medicinal cannabis oil, did not significantly impair overall driving performance but did lead to increased variability in speed and weaving during a simulated drive, particularly noticeable between 20 and 30 minutes after administration.

Changes in eye behavior, such as increased fixation duration and altered blink patterns, suggest that eye tracking could be a useful tool for assessing cannabis-related driver impairment.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effect of CannEpil&#174; on simulated driving performance and co-monitoring of ocular activity: A randomised controlled trial. Manning, B., Hayley, AC., Catchlove, S., et al.[2023]

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]

A review of 36 studies indicates that THC, the main psychoactive component of cannabis, significantly impairs psychomotor skills and cognitive functions, negatively affecting driving ability.

Drivers under the influence of cannabis are at a much higher risk of accidents, with studies showing that cannabis use can double or triple the likelihood of a crash, particularly when combined with alcohol.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Neurocognitive Correlates in Driving Under the Influence of Cannabis. Busardò, FP., Pellegrini, M., Klein, J., et al.[2018]

Citations

1. clinicaltrials.gov clinicaltrials.gov/study/NCT06218550

Delta-8-THC vs. Delta-9-THC on Simulated Driving ... The present study will evaluate the dose effects of delta-8-THC, compared with delta-9-THC, on simulated driving performance, field sobriety tests, cognitive ...

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

Cannabis Effects on Driving Performance Cannabis may affect driving performance acutely (in the short-term) or over the long-term if a person is using sufficient quantities of cannabis for a ...

3. researchgate.net researchgate.net/publication/379691690_Driving_Under_the_Influence_of_Alcohol_Cannabis_and_Delta-8_THC_Perceived_Likelihood_Risk_Perceptions_and_Behaviors

Perceived Likelihood, Risk Perceptions, and Behaviors Pairwise t tests compared delta-8-THC effect rating items; one-sample t tests examined responses to delta-9-THC comparison items. Results: Most delta-8-THC ...

4. withpower.com withpower.com/trial/early-phase-1-confusion-2-2024-ae3bd

THC for Driving Performance · Info for Participants THC, specifically Delta-8-THC and Delta-9-THC, is unique in its ability to impair driving performance by affecting cognitive and psychomotor skills, which are ...

5. aaafoundation.org aaafoundation.org/wp-content/uploads/2025/02/202503-AAAFTS-Cannabis-Driving-Messaging.pdf

Examination of Cannabis Users' Perceptions and Self- ... One common myth reported by SMEs is that cannabis improves driving ability or enhances focus, making users believe they are safer drivers. Another ...

6. ajpmonline.org ajpmonline.org/article/S0749-3797(25)00504-5/fulltext

U.S. State Marijuana and Delta-8-Tetrahydrocannabinol ... The results of this study suggest that delta-8-THC use is highest in environments that restrict marijuana use and lower in states that ...

7. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC8792796/

Driving Performance and Cannabis Users' Perception ... This randomized clinical trial studies the magnitude and time course of effects of cannabis on driving, effect of cannabis with different tetrahydrocannabinol ...

8. reddit.com reddit.com/r/madisonwi/comments/1gqdewg/uwmadison_researchers_are_testing_the_influence/

UW-Madison researchers are testing the influence of delta ... Driving on delta-8-THC is currently legal in Wisconsin. Let's study it and change that if we can find evidence of impairment comparable to other regulated ...

9. clinicaltrial.be clinicaltrial.be/fr/details/422567?per_page=100&only_recruiting=1&only_eligible=0&only_active=0

Delta-8-THC vs. Delta-9-THC on Simulated Driving ... The present study will characterize the acute effects of oral and inhaled ∆8-THC, compared with a positive control dose of ∆9-THC and placebo, ...