Cannabis Driving Research

Detection of Δ9-Tetrahydrocannabinol Impairment Using Resting-State Functional Near-Infrared Spectroscopy: A Randomized Clinical Trial.

Berchansky, Moshe · 2026

Resting-state fNIRS achieved ROC-AUC=0.87, accuracy=0.90, and false-positive rate=0.05 for THC impairment detection vs.

Recent Advances in the Science of Cannabis-Impaired Driving.

Metrik, Jane · 2026

THC acutely impairs driving performance consistently within the first hour of use, with impairment remaining for approximately 4-5 hours post-inhalation.

Relationships of Changing State Cannabis Policies With Alcohol Policy Effectiveness and Alcohol or Cannabis Involvement in Motor Vehicle Fatalities.

Naimi, Timothy S · 2026

A 10-point increase in alcohol policy scores was associated with 6.3% lower odds of alcohol-involved crash fatalities.

Partial cannabis legalization and the increase of the THC threshold in road traffic: a statistical analysis of traffic cases before and after legal changes.

Wohlfarth, Ariane · 2026

Median THC levels in administrative and criminal traffic offenses were identical (3.44 ng/mL).

The Alarming Surge of Driving Under the Influence-Related Motor Vehicle Crashes.

Al Ma'ani, Mohammad · 2025

Analysis of 683,184 motor vehicle crash drivers at US trauma centers found that 28.8% tested positive for drugs or alcohol, with 36.3% of those testing positive for multiple substances.

Association of driving with blood delta-9-tetrahydrocannabinol: a systematic review.

Behzad, Danial · 2025

Of 12 studies meeting inclusion criteria, 10 found no significant linear correlations between blood THC and driving measures.

Driving under the influence of alcohol and cannabis: Associations with substance use and behavioral health characteristics.

Choi, Namkee G · 2025

DUIC prevalence (20.6%) more than double DUIA (8.6%); age 65+ was a DUIC risk factor; substance disorders, early initiation, mental health problems, and criminal justice involvement predicted both; DUIC higher in medical cannabis legal states..

Cannabis and driving: A repeat cross-sectional analysis of driving after cannabis use pre- vs. post-legalization of recreational cannabis in Canada.

Kucera, Ava · 2025

Overall driving after use rose from 5.7% (2018) to 8.8% (2022, OR=1.43) and 7.6% (2023, OR=1.20).

The association between single and dual use of cannabis and alcohol and driving under the influence and riding with an impaired driver in a large sample of Canadian adolescents.

Gohari, Mahmood R · 2024

Overall, 14.7% of students reported impaired driving or riding (IDR).

Young Adult Alcohol and Cannabis Impaired Driving After the Opening of Cannabis Retail Stores in Washington State.

Hultgren, Brittney A · 2024

From 2014 to 2019, alcohol DUI decreased overall (AOR 0.93) and among drinkers (AOR 0.95).

The Effect of Nabiximols on Driving Ability in Adults with Chronic Tic Disorders: Results of a Substudy Analysis of the Double-Blind, Randomized, Placebo-Controlled CANNA-TICS Trial.

Müller-Vahl, Kirsten R · 2024

Fitness to drive increased from 55.8% to 71.8% in the nabiximols group over 13 weeks, while it decreased from 66.7% to 52.6% in placebo.

Special Report from the CDC: Driving under the influence of alcohol, marijuana, or other illicit drugs among drivers aged ≥16 years - National Survey on Drug Use and Health, 2016-2019.

Schumacher, Amy C · 2024

In 2019, 5.3% of US drivers reported driving under the influence of marijuana in the past year, up from 4.5% in 2016.

Evaluating possible 'next day' impairment in insomnia patients administered an oral medicinal cannabis product by night: a pilot randomized controlled trial.

Suraev, Anastasia · 2024

At 9+ hours after evening administration of 10mg THC/200mg CBD oil, there were no differences from placebo on 27 of 28 cognitive and psychomotor tests, including simulated driving performance.

Detection of Δ9-tetrahydrocannabinol (THC) in oral fluid using two point-of-collection testing devices following oral administration of a THC and cannabidiol containing oil.

Suraev, Anastasia · 2024

At 30 minutes post-dose, oral fluid THC concentrations varied widely (0-425 ng/mL), and both devices showed poor sensitivity (Securetec: 25%, Drager: 50%).

Driving under the influence of cannabis, alcohol, and illicit drugs among adults in the United States from 2016 to 2020.

Myers, Matthew G · 2023

Using nationally representative NSDUH data, over 1 in 10 US adults reported DUI of any substance annually.

Driving under the influence of cannabis and alcohol: Evidence from a national sample of young drivers.

Salas-Wright, Christopher P · 2023

DUI-cannabis prevalence was 6.3% in the full sample and 24.5% among past-year cannabis users.

Driving Performance and Cannabis Users' Perception of Safety: A Randomized Clinical Trial.

Marcotte, Thomas D · 2022

THC significantly impaired the Composite Drive Score at 30 minutes (d=0.59) and 1.5 hours (d=0.55), with borderline impairment at 3.5 hours (d=0.29) and no difference at 4.5 hours.

Are blood and oral fluid Δ9-tetrahydrocannabinol (THC) and metabolite concentrations related to impairment? A meta-regression analysis.

McCartney, Danielle · 2022

Higher blood THC, 11-OH-THC, oral fluid THC, and subjective intoxication were associated with greater impairment in occasional users, but correlations were negligible to weak (r = -0.08 to -0.43).

Correlation between oral fluid and blood THC concentration: A systematic review and discussion of policy implications.

Robertson, M B · 2022

Oral fluid THC reliably detected presence of THC in blood (71.2% sensitivity, 97.7% specificity).

The effects of cannabis and alcohol on driving performance and driver behaviour: a systematic review and meta-analysis.

Simmons, Sarah M · 2022

Cannabis alone impaired lateral control (lane weaving) and decreased driving speed.

Canada's cannabis legalization and drivers' traffic-injury presentations to emergency departments in Ontario and Alberta, 2015-2019.

Callaghan, Russell C · 2021

There was no evidence of significant changes in traffic-injury ED visits after cannabis legalization in either province, for all drivers or youth drivers specifically.

Blood and Oral Fluid Cannabinoid Profiles of Frequent and Occasional Cannabis Smokers.

Hoffman, Melissa A · 2021

Frequent users had higher residual blood THC and were more likely to test positive before even smoking.

Biomarkers of Recent Cannabis Use in Blood, Oral Fluid and Breath.

Hubbard, J A · 2021

Oral fluid THC at 10 ng/mL cutoff showed 99.7% specificity, 82.4% sensitivity, 92.5% positive predictive value, and 99.2% negative predictive value for detecting cannabis use within 3 hours.

Cohort study of medical cannabis authorization and motor vehicle crash-related healthcare visits in 2014-2017 in Ontario, Canada.

Lee, Cerina · 2021

After accounting for an initial decrease in MVC-related visits (-2.42/10,000 patients immediately post-authorization), there was a significant increasing trend (+0.89 events/10,000 relative to controls, p=0.0019).

Determining the magnitude and duration of acute Δ9-tetrahydrocannabinol (Δ9-THC)-induced driving and cognitive impairment: A systematic and meta-analytic review.

McCartney, Danielle · 2021

At peak effect, THC significantly impaired lateral control, tracking, and divided attention.

Prevalence and Correlates of Driving Under the Influence of Cannabis in the U.S.

Salas-Wright, Christopher P · 2021

Using NSDUH data from 128,205 adults, researchers found that 29.5% of cannabis users reported driving under the influence, with daily users showing a 57% predicted probability and those with cannabis use disorder reaching 63.8%..

Estimating Cannabis Involvement in Fatal Crashes in Washington State Before and After the Legalization of Recreational Cannabis Consumption Using Multiple Imputation of Missing Values.

Tefft, Brian C · 2021

Using multiple imputation to account for untested drivers, the proportion of THC-positive drivers in fatal crashes rose from 9.3% before to 19.1% after legalization (adjusted PR=2.3, 95% CI: 1.3-4.1).

Effect of Cannabidiol and Δ9-Tetrahydrocannabinol on Driving Performance: A Randomized Clinical Trial.

Arkell, Thomas R · 2020

THC-dominant and THC/CBD-equivalent cannabis significantly increased lane weaving (SDLP +2.33cm and +2.81cm respectively) at 40-100 minutes after vaporization.

Odds of culpability associated with use of impairing drugs in injured drivers in Victoria, Australia.

Drummer, Olaf H · 2020

THC-positive drivers had modestly increased culpability odds (OR 1.9, 95% CI: 1.2-3.1).

Impact of cannabis and low alcohol concentration on divided attention tasks during driving.

Miller, Ryan E · 2020

In a randomized, placebo-controlled crossover driving simulator study, each 1 ug/L increase in blood THC predicted increased odds of failing to complete a console search task (OR 1.05), more incorrect responses (OR 1.05), speed declines during mirror tasks, and longer lane departures.

Pharmacodynamic dose effects of oral cannabis ingestion in healthy adults who infrequently use cannabis.

Schlienz, Nicolas J · 2020

In a placebo-controlled study with 17 infrequent cannabis users, 10 mg THC produced discriminable subjective effects and elevated heart rate but did not impair cognition.

Pharmacokinetics of Cannabis Brownies: A Controlled Examination of Δ9-Tetrahydrocannabinol and Metabolites in Blood and Oral Fluid of Healthy Adult Males and Females.

Spindle, Tory R · 2020

After consuming cannabis brownies (0, 10, 25, or 50 mg THC), blood THC and 11-OH-THC peaked at 1.5-2 hours and returned to baseline within 8 hours.

Cannabis use as a risk factor for causing motor vehicle crashes: a prospective study.

Brubacher, Jeffrey R · 2019

No increased crash risk in drivers with THC <2 or 2-5 ng/mL.

Public health implications of legalising the production and sale of cannabis for medicinal and recreational use.

Hall, Wayne · 2019

Cannabis legalisation has been associated with increased use in some populations and possible increases in road crashes.

The annual cannabis holiday and fatal traffic crashes.

Harper, Sam · 2019

Between 1992 and 2016, April 20th showed a non-significant 12% increase in fatal crash involvement relative to control days one week apart (IRR 1.12, 95% CI: 0.97-1.28), but no increase when compared to broader control periods or all other days (IRR 0.98, 95% CI: 0.88-1.10)..

Drivers who tested positive for cannabis in oral fluid: a longitudinal analysis of administrative data for Spain between 2011 and 2016.

Herrera-Gómez, Francisco · 2019

Of 65,244 confirmed drug-positive tests (2011-2016), 51,869 (79.5%) were THC-positive.

US Epidemiology of Cannabis Use and Associated Problems.

Hasin, Deborah S · 2018

This comprehensive review documented the shifting landscape of cannabis use in the United States. Both adults and adolescents increasingly perceive cannabis as harmless.

Neurocognitive Correlates in Driving Under the Influence of Cannabis.

Busardò, Francesco P · 2017

The review synthesized findings from 36 studies on cannabis and driving.

Pharmacokinetic Profile of Oral Cannabis in Humans: Blood and Oral Fluid Disposition and Relation to Pharmacodynamic Outcomes.

Vandrey, Ryan · 2017

Six healthy adults per dose received cannabis brownies containing 10, 25, or 50 mg THC, with specimens collected for 9 days. Blood THC concentrations were remarkably low: mean peak levels were only 1, 3.5, and 3.3 ng/mL for the three doses, far lower than levels seen after smoking.

A systematic review of passive exposure to cannabis.

Berthet, Aurélie · 2016

This systematic review identified biomarkers that can distinguish passive cannabis smoke exposure from active use across multiple biological matrices. In everyday conditions, urinary THC-COOH levels from passive exposure should fall below standard positivity thresholds, especially when normalized to creatinine levels.

The involvement of prescribed drugs in road trauma.

Drummer, Olaf H · 2016

Researchers reviewed coroner files and toxicology records of 2,638 fatally injured drivers in Victoria, Australia over 14 years (2000-2013), representing over 97% of all driver fatalities in the study period. Drugs were found in 34.4% of fatalities.

Free and Glucuronide Whole Blood Cannabinoids' Pharmacokinetics after Controlled Smoked, Vaporized, and Oral Cannabis Administration in Frequent and Occasional Cannabis Users: Identification of Recent Cannabis Intake.

Newmeyer, Matthew N · 2016

Researchers gave the same dose of cannabis to both frequent and occasional users through three routes: smoking, vaporizing, and eating.

Protein kinase B (AKT1) genotype mediates sensitivity to cannabis-induced impairments in psychomotor control.

Bhattacharyya, S · 2014

In a double-blind study, healthy occasional cannabis users received either THC or placebo and performed a response inhibition task during brain imaging.

Acute cannabis consumption and motor vehicle collision risk: systematic review of observational studies and meta-analysis.

Asbridge, Mark · 2012

Researchers searched 19 databases without language or year restrictions and identified 9 observational studies meeting inclusion criteria.

Cognition and motor control as a function of Delta9-THC concentration in serum and oral fluid: limits of impairment.

Ramaekers, J G · 2006

Twenty recreational cannabis users participated in a double-blind, placebo-controlled, three-way crossover study with single doses of 0, 250, and 500 micrograms/kg THC by smoking.

Police-Reported Impaired Driving After Recreational Cannabis Legalization in Canada.

Armstrong, Michael J · 2026

Post-2018, police reported 65 extra drug-impaired incidents per million annually (42% above trend) and 280 extra alcohol-impaired incidents per million (17% above trend); increases were associated more with drug recognition expert employment and pandemic restrictions than cannabis sales..

Driving after cannabis consumption among US adults ages 50 years and older: A short communication.

Bonar, Erin E · 2026

20.2% of past-year cannabis users aged 50+ reported driving within 2 hours of consumption; daily use (OR=3.31), male sex (OR=1.72), and mental health motives (OR=1.93) were independent predictors of cannabis-impaired driving..

Risk Perceptions Related to Driving After Use of Alcohol and Cannabis in a Cross-National Sample of University Students in 6 Countries.

Csölle, Kianna · 2026

Less than 12% of students across all countries endorsed impaired driving.

The Devil is in the Details: Exploring the Impact of Risk Behavior Detail (RBD) in Health Messages Targeting Cannabis-Impaired Driving.

Eliash-Fizik, Hadar · 2026

Exposure to high-detail messages about cannabis-impaired driving was associated with increased DUIC intentions and behaviors, both immediately and at two-week follow-up.

Characteristics of trauma patients involved in motor vehicle collisions before and after legalization of medical marijuana in Pennsylvania.

Gimbel, Kirsten · 2026

Following medical marijuana legalization, marijuana positivity among MVC trauma patients increased significantly (p<0.0001), with marijuana-positive patients having longer hospital stays (+2 days) and higher rates of polysubstance use compared to marijuana-negative patients..

Pass the Keys: Using Behavioral Economics to Explore Driving After Cannabis Use.

Miller, Brandon P · 2026

Cannabis demand (how much people would purchase and consume) was sensitive to driving latency: participants consumed more when driving was 6 hours away versus 20 minutes away.

Parental sociodemographic profiles in relation to mental health, cannabis use motives, and cannabis use behaviors among a sample of US young adult parents.

Romm, Katelyn F · 2026

Four distinct parent profiles emerged.

Short-term effects of cannabis legalisation in Germany on driving under the influence of cannabis: a difference-in-differences analysis using Austria as a control.

Schranz, Anna · 2026

German cannabis use rose from 12.1% to 14.4%, but this did not significantly differ from Austrian trends (DiD OR 1.18, 95% CI 0.95-1.48).

Evaluation of the causal impact of recreational marijuana legalisation on traffic safety in the US.

Anupriya · 2025

Using an augmented synthetic control method to generate causal inference, the study identified a consistent but lagged pattern of increased traffic fatality rates in several states following recreational marijuana legalization.

Integrating crash and fluids toxicology data to examine injury outcomes and associated driver behaviors.

Auguste, Marisa E · 2025

Drivers who tested positive for alcohol alone, cannabis alone, or a combination of substances had significantly higher odds of injury in motor vehicle crashes.

Driving and cannabis use: a questionnaire about knowledge and behaviors after the legalization of recreational cannabis in California.

Baird, Sara · 2025

Among 4,020 current cannabis users in California, 62% knew about the in-vehicle consumption ban, 59% knew containers must be sealed, and 74% knew DUIC citations are possible.

State Nonmedical Cannabis Laws and U.S. Young Adults' Cannabis-Related Experiences.

Berg, Carla J · 2025

Retail license limits were associated with fewer retailer visits.

Cannabis use characteristics and associations with problematic use outcomes, quitting-related factors, and mental health among US young adults.

Berg, Carla J · 2025

Four cannabis use classes emerged: infrequent-herb/edibles (41.4%), moderate-herb (28.0%), frequent-herb (16.8%), and moderate-oil/other (13.8%).

Impact of naturalistic cannabis use on lateral control and speed: A driving simulator study.

Brooks-Russell, Ashley · 2025

Occasional flower users had a significant increase in lane departures after cannabis use (0.16/min at baseline to 0.47/min 30 minutes post-use).

Pupillary dynamics as a marker of acute cannabis inhalation.

Brooks-Russell, Ashley · 2025

The most predictive pupillary measure was percent change in pupil size, which decreased after cannabis use, with an area under the curve of 0.73 at 40 minutes and 0.75 at 100 minutes.

Prevalence of Impairing Substance Use in Injured Drivers.

Brubacher, Jeffrey R · 2025

This is one of the largest and most rigorous studies of substance use among injured drivers ever conducted.

"Stoned on the road": A systematic review of cannabis-impaired driving educational initiatives targeting young drivers in Canada.

Colonna, Robert · 2025

Fifteen Canadian DUIC initiatives were found: seven educational programs and eight awareness campaigns spanning national and regional levels.

Per Se Driving Under the Influence of Cannabis Statutes and Blood Delta-9-Tetrahydrocannabinol Concentrations following Short-Term Cannabis Abstinence.

Fitzgerald, Robert L · 2025

Among 190 regular cannabis users who abstained for at least 48 hours, 43% exceeded zero-tolerance THC limits (0.5+ ng/mL), 24% exceeded the 2 ng/mL per se limit, and 5.3% exceeded 5 ng/mL.

Haven't I waited long enough? The role of wait times and subjective impairment in cannabis-related driving behavior.

Har-Even, Ayelet · 2025

Of 979 cannabis users, 23% drove within 2 hours of use (high risk), 37% waited 3-6 hours (moderate risk), and 40% waited 7+ hours (low risk).

Quantitative and qualitative changes in substance-related administrative offences in road traffic during the SARS-CoV-2 pandemic in Munich.

Holzer, Anna · 2025

Among 6,210 blood samples from substance-related traffic stops in Munich (2019-2021), cannabis was detected most frequently (66-67%), followed by alcohol (11%) and cocaine (5%).

Individual application patterns of Cannabis-based Medicines in Germany - Descriptive evaluation of a patient survey and discussion from a forensic perspective.

Hundertmark, Marica · 2025

Among 1,030 German medical cannabis patients, 89.9% used cannabis flowers.

Cannabis consumption and motor vehicle collision: A systematic review and meta-analysis of observational studies.

Jin, Andrew · 2025

Across 31 studies with 328,388 individuals, cannabis consumption was associated with increased risk of MVC fatality (OR=1.55, 95% CI: 1.20-1.98) with 14 more deaths per 100,000 MVCs, and increased risk of injury (OR=2.00, 95% CI: 1.31-3.07) with an absolute risk increase of 6.8%.

Evaluation of Cannabis Per Se Laws: A Semi-Mechanistic Pharmacometrics Model for Quantitative Characterization of THC and Metabolites in Oral Users.

Li, Peizhi · 2025

Using data from 10 published studies, researchers built a model simulating THC blood levels in frequent and occasional users after oral doses from 2.5 to 100 mg.

Cannabis in road traffic - a retrospective analysis to identify possible cut-off-values.

Ludwig, A · 2025

THC serum concentrations were slightly but significantly higher in cases with criminal driving offenses compared to those without, but the absolute differences were small with too much overlap between groups to define a useful cut-off.

Metabolomic profiling of cannabis use and cannabis intoxication in humans.

Madrid-Gambin, Francisco · 2025

Occasional and chronic cannabis users had distinctly different metabolic fingerprints at baseline (not intoxicated).

The driving-related attitudes, beliefs and behaviours of cannabis users in the Australian Capital Territory following decriminalisation.

McCartney, Danielle · 2025

67.9% of participants reported waiting 7+ hours before driving, but 21.5% reported waiting 3 hours or less.

A randomized, placebo-controlled, double-blind, pilot study of cannabis-related driving impairment assessed by driving simulator and self-report.

Meda, Shashwath A · 2025

In a controlled simulator study, cannabis administration led to measurable driving impairment including lane weaving and reaction time delays, even when participants self-reported feeling capable of driving..

The effects of orally ingested Delta-9-Tetrahydrocannabinol on drivers' hazard perception and risk-taking behaviours: A within-subjects study of medicinal cannabis users.

Mieran, Taren · 2025

Among 41 medicinal cannabis users, oral THC did not significantly impair hazard perception skill, but participants chose slower speeds and longer following distances after consumption.

Impact of Canada's Cannabis Act on drug- and alcohol-related collisions in Québec: an interrupted time-series analysis of five major cities.

Nazif-Munoz, José Ignacio · 2025

Total cannabis sales were significantly associated with a 12% increase in drug-related crashes (IRR 1.12) and a 12% increase in alcohol-related crashes (IRR 1.12) across five Quebec cities.

A comparison of the prevalence of cannabis and alcohol use among drivers and passengers in British Columbia and Ontario, Canada.

Pei, Lulu X · 2025

This study analyzed toxicology data from 3,004 drivers and 941 passengers who were moderately injured in motor vehicle accidents across British Columbia and Ontario.

Changes in blood cannabinoid concentrations over multiple collection times in driving under the influence of drugs casework.

Peterson, Brianna L · 2025

In 35 DUID cases with multiple blood draws (81 total samples), THC concentrations ranged from 0.74 to 40 ng/mL.

The use of prescription medication and other drugs by New Zealand drivers with illegal blood alcohol levels.

Poulsen, Helen · 2025

Among 3,050 drivers with blood alcohol exceeding legal limits in New Zealand (2011-2015), 41% had used alcohol in combination with other drugs.

Correlates of driving under the influence of cannabis: A latent class analysis.

Schranz, Anna · 2025

Three classes emerged: 'Low risk' (48%) with minimal DUIC and risky behaviors; 'DUIC-specific risk' (30%) with high cannabis-impaired driving, peers who also drive high, and low perceived risk, but no other risky behaviors; and 'Global risk' (22%) with multiple risky behaviors and risk factors.

Influence of cannabis and alcohol on motor vehicle injury severity in Canadian trauma centres: a prospective study.

Simmons, Sarah M · 2025

Drivers with any detectable alcohol had increased odds of hospital admission (aOR 1.36-1.69), but THC did not modify the relationship between alcohol and admission.

Evaluating risks, monitoring cannabis use, and planning to get home safely: Exploring self-regulation processes associated with cannabis use and driving.

Sukhawathanakul, Paweena · 2025

Cannabis users showed substantial heterogeneity in self-regulation processes related to driving.

Edible cannabis use on simulated driving performance.

Won, Nae Y · 2025

Edible cannabis impaired simulated driving performance across speed control and lane maintenance measures, with daily users showing different patterns than occasional users, and effects varying between rural and urban driving scenarios..

Event-level influences of alcohol, cannabis, and simultaneous use on perceived driving risk.

Wycoff, Andrea M · 2025

Simultaneous alcohol and cannabis use increased perceived driving impairment, yet participants were 3.7x more willing to drive within an hour compared to alcohol-only use, suggesting cannabis may attenuate alcohol's deterrent effect on driving decisions..

Toxicology findings from drivers suspected of drug-impaired driving in Ontario (2008-2019).

Beirness, Douglas J · 2024

Over 12 years, 5,388 samples from suspected drug-impaired drivers were analyzed.

Attitudes toward driving after cannabis use: a systematic review.

Boicu, Bianca · 2024

Six themes emerged: (1) attitudes are mixed (35 studies negative, 20 studies with opposing views); (2) youth, men, and frequent users view DACU more favorably; (3) attitudes predict past and intended DACU; (4) DACU viewed more favorably than drunk driving; (5) relationship with legalization unclear; (6) perceived apprehension risk is low to moderate..

Effects of acute cannabis inhalation on reaction time, decision-making, and memory using a tablet-based application.

Brooks-Russell, Ashley · 2024

Occasional users showed significant decrements in reaction time and short-term memory after smoking cannabis.

Risk of motor vehicle collision associated with cannabis and alcohol use among patients presenting for emergency care.

Choo, Esther K · 2024

Cannabis alone was not associated with higher MVC odds.

Trends in Driving Under the Influence of Alcohol and Cannabis Among Young Adults in Washington State From Before to During the COVID-19 Pandemic.

Hultgren, Brittney A · 2024

Pre-pandemic trends in DUI prevalence and pandemic-year deviations were both small and not statistically significant.

Young adult impaired driving behaviors and perceived norms of driving under the influence of simultaneous alcohol and cannabis use.

Hultgren, Brittney A · 2024

DUI after simultaneous alcohol and cannabis use (DUI-SAM) was reported by 2.7% and riding with an impaired driver (RWI-SAM) by 5.3%.

Factors related to the low-risk perception of driving after cannabis use.

Huỳnh, Christophe · 2024

Lower risk perception of driving after cannabis use was associated with being male, weekly-to-daily cannabis use, personal engagement in cannabis-impaired driving, general risky driving behaviors, being a passenger with an impaired driver, number of friends who drive after cannabis use, and peer approval.

Media Framing of Causes, Risks, and Policy Solutions for Cannabis-Impaired Driving: Does Medical vs. Non-Medical Cannabis Context Matter?

Lewis, Nehama · 2024

News coverage of non-medical cannabis DUI was more likely to emphasize individual causes (vs social/political), describe drivers negatively, refer to increased accident risk, and call for enforcement.

A systematic review of oculomotor deficits associated with acute and chronic cannabis use.

Manning, Brooke · 2024

Across 20 studies, acute THC consumption increased saccadic latency, reduced accuracy, and impaired inhibitory control.

Cannabis policy bundles and traffic fatalities in the American States over time.

Park, Mingean · 2024

The permissive cannabis policy bundle (broader access, home cultivation, etc.) was associated with lower overall traffic fatality rates.

Delays in blood collection and drug toxicology results among crash-involved drivers arrested for impaired driving.

Price, Jana M · 2024

When a driver is arrested for impaired driving after a crash, how long does it take to actually draw blood for testing? This study analyzed 8,923 crash-involved DUI cases in Wisconsin over three years and found the average delay was 1.8 hours — with significant variation based on crash severity. More severe crashes caused longer delays.

Reliability of roadside oral fluid testing devices for ∆9-tetrahydrocannabinol (∆9-THC) detection.

Scherer, Juliana Nichterwitz · 2024

The Drager DrugTest had 96.8% sensitivity and 97.1% specificity for detecting THC at a 5 ng/mL threshold.

A study into the nature and extent of polydrug use in driving recidivism behavior.

Tassoni, Giovanna · 2024

Polydrug use was a significant risk factor for driving recidivism compared to monodrug use (OR=1.99).

Accuracy and replicability of identifying eyelid tremor as an indicator of recent cannabis smoking.

Wang, George Sam · 2024

There was no significant association between recent cannabis use and eyelid tremor presence.

Examining the impact of legalization on the prevalence of driving after using cannabis: A comparison of rural and non-rural parts of Canada.

Wrathall, Meghan · 2024

Rural residents showed a significant increase in driving after cannabis use directly following legalization, which returned to pre-legalization rates one year later.

The effect of cannabis edibles on driving and blood THC.

Zhao, S · 2024

Cannabis edibles produced a decrease in mean speed at 2 hours post-consumption but not at 4 or 6 hours.

Driving-related behaviors, attitudes, and perceptions among Australian medical cannabis users: results from the CAMS 20 survey.

Arkell, Thomas R · 2023

28% of driving respondents reported DUIC.

Self-reported impacts of recreational and medicinal cannabis use on driving ability and amount of wait time before driving.

Auguste, M E · 2023

Cannabis use frequency predicted both lower self-reported driving impairment and shorter wait time before driving.

Workplace and non-workplace cannabis use and the risk of workplace injury: Findings from a longitudinal study of Canadian workers.

Carnide, Nancy · 2023

Among 2,745 Canadian workers followed from 2018-2020, workplace cannabis use (before or at work) was associated with a nearly two-fold increased risk of workplace injury (RR 1.97, 95% CI 1.32-2.93).

Associations of cannabis use with motor vehicle crashes and traffic stops among older drivers: AAA LongROAD study.

Davis, Shelby · 2023

Of 2,095 active drivers aged 65-79, 186 (8.9%) used cannabis in the past year.

Driving under the influence of cannabis: A 5-year retrospective Italian study.

Favretto, Donata · 2023

When a driver is stopped for suspected impaired driving, the time between the traffic stop and the blood draw matters enormously for cannabis detection.

Can inhaled cannabis users accurately evaluate impaired driving ability? A randomized controlled trial.

Hartley, Sarah · 2023

One of the most important questions in cannabis and driving is whether users can tell when they're too impaired to drive.

Cannabis-Involved Traffic Injury Emergency Department Visits After Cannabis Legalization and Commercialization.

Myran, Daniel T · 2023

Annual rates of cannabis-involved traffic injury ER visits rose from 0.18 to 1.01 per 1,000 total motor vehicle collisions.

Drug-impaired driving and traffic collisions: Study on a cross section of the Italian population.

Odoardi, Sara · 2023

Among 1,236 drivers in crashes, alcohol was most common (19% non-fatal, 32% fatal), followed by cannabinoids (12% non-fatal) and cocaine (9% non-fatal, 20% fatal).

Collisions and cannabis: Measuring the effect of recreational marijuana legalization on traffic crashes in Washington State.

Voy, Annie · 2023

Traffic collisions increased following both the legalization of recreational cannabis and the opening of retail stores in Washington State.

Roadside screening tests for cannabis use: A systematic review.

Wennberg, Erica · 2023

Available roadside screening devices, primarily oral fluid-based, can detect THC presence but their ability to identify functional impairment is limited.

Rating the comparative efficacy of state-level cannabis policies on recreational cannabis markets in the United States.

Blanchette, Jason G · 2022

State monopoly (government-owned production through retail) was rated most effective across all three outcome areas.

Developments and Changes in Primary Public Health Outcome Indicators Associated with the Legalization of Non-Medical Cannabis Use and Supply in Canada (2018): A Comprehensive Overview.

Boury, Himani · 2022

Cannabis use increased in select population groups, with a shift away from smoking toward other consumption methods.

A study of self-reported personal cannabis use and state legal status and associations with engagement in and perceptions of cannabis-impaired driving.

Brown, Timothy · 2022

Each year of delayed cannabis onset was associated with 0.51 fewer use days/month and a lower proportion of driving-after-use days.

Perceived effects of cannabis: Generalizability of changes in driving performance.

Burt, Thomas S · 2022

Subjective perceptions of cannabis impairment significantly predicted driving performance measures (lane position, speed control) beyond the effect of THC dose.

Road traffic injury risk from alcohol and cannabis use among emergency department patients in Argentina.

Conde, Karina · 2022

Alcohol use increased road traffic injury risk 6.78-fold (95% CI 3.75-12.25).

Cannabis legalization and driving under the influence of cannabis in a national U.S. Sample.

Dutra, Lauren M · 2022

Among 1,249 past-30-day cannabis users, the risk of driving within 3 hours of getting high was 59% lower in recreational states (RR 0.41) and 61% lower in medical-only states (RR 0.39) compared to states without legal cannabis.

Combined effect of alcohol and cannabis on simulated driving.

Fares, Andrew · 2022

The combination of alcohol (target BAC 0.08%) and cannabis (12.5% THC) significantly increased standard deviation of lateral position (weaving) compared to placebo and to either drug alone.

Identification of ∆9-tetrahydrocannabinol (THC) impairment using functional brain imaging.

Gilman, Jodi M · 2022

In 169 cannabis users given oral THC or placebo in a crossover design, prefrontal cortex oxygenated hemoglobin increased after THC only in participants classified as impaired.

Does expanding access to cannabis affect traffic crashes? County-level evidence from recreational marijuana dispensary sales in Colorado.

Gunadi, Christian · 2022

Using county-level variation in when recreational dispensaries opened across Colorado, the entry of cannabis retail stores was associated with a significant increase in marijuana-related hospital discharges but no increase in traffic crash incidents.

Typologies of Canadian young adults who drive after cannabis use: A two-step cluster analysis.

Huỳnh, Christophe · 2022

Four subgroups emerged: (1) frequent cannabis users who regularly drive after using; (2) individuals with generalized deviance, diverse risky road behaviors, and high psychological distress; (3) alcohol and drug-impaired drivers who were also heavy drinkers; and (4) well-adjusted youths with mild depressive-anxious symptoms..

Effects of High-Potency Cannabis on Psychomotor Performance in Frequent Cannabis Users.

Karoly, Hollis C · 2022

Peak psychomotor impairment occurred immediately after cannabis use, with significant recovery by one hour post-use.

Cannabis legalization and traffic injuries: exploring the role of supply mechanisms.

Kilmer, Beau · 2022

Total cannabis registrations were not associated with traffic crashes.

A Clinical Framework for Assessing Cannabis-Related Impairment Risk.

MacCallum, Caroline A · 2022

The framework provides clinicians with a structured approach to evaluate impairment-related factors in medical cannabis patients, including dosing, tolerance, timing, and individual risk factors.

Effects of cannabidiol on simulated driving and cognitive performance: A dose-ranging randomised controlled trial.

McCartney, Danielle · 2022

Non-inferiority analyses established that CBD at 15, 300, and 1,500 mg did not impair driving performance beyond a threshold equivalent to 0.05% blood alcohol.

Orally administered cannabidiol does not produce false-positive tests for Δ9 -tetrahydrocannabinol on the Securetec DrugWipe® 5S or Dräger DrugTest® 5000.

McCartney, Danielle · 2022

Among 259 DrugWipe 5S and 256 DrugTest 5000 tests following oral CBD administration (placebo, 15, 300, or 1,500 mg), no THC-positive results were observed.

Influence of cannabis use history on the impact of acute cannabis smoking on simulated driving performance during a distraction task.

Miller, Ryan · 2022

Occasional cannabis users (1-2 times/week) had significantly increased lane departure risk during distraction after acute cannabis use (OR=3.71, P=0.04).

Comparison of the effects of alcohol and cannabis on visual function and driving performance. Does the visual impairment affect driving?

Ortiz-Peregrina, Sonia · 2022

Both alcohol (300 ml and 450 ml wine) and cannabis significantly impaired visual function scores.

Cannabis Adaptation During and After Alcohol Ignition Interlock Device Installation: A Longitudinal Study.

Scherer, Michael · 2022

Among 189 DUI-convicted drivers, those who decreased alcohol use while an ignition interlock device was installed significantly increased cannabis use, which continued to rise after the device was removed..

Separate and combined effects of alcohol and cannabis on mood, subjective experience, cognition and psychomotor performance: A randomized trial.

Wickens, Christine M · 2022

Cannabis increased tension-anxiety, confusion, euphoria, and sedation ratings but had minimal impact on cognitive test scores.

The Impact of Cannabis Decriminalization and Legalization on Road Safety Outcomes: A Systematic Review.

Windle, Sarah B · 2022

Medical legalization was associated with reductions in fatal motor vehicle collisions, while recreational legalization was associated with increases.

Young and under the influence: A systematic literature review of the impact of cannabis on the driving performance of youth.

Alvarez, Liliana · 2021

Class II evidence suggests THC is likely to reduce mean speed, headway distance, and reaction time, and increase lane and steering wheel position variability in young drivers.

Cannabis, alcohol and other drug findings in fatally injured drivers in Ontario.

Beirness, Douglas J · 2021

Among 921 driver fatalities, 53.7% tested positive for at least one substance.

Cannabis, Impaired Driving, and Road Safety: An Overview of Key Questions and Issues.

Brands, Bruna · 2021

Cannabis contributes to crash risk, but key questions remain unanswered: the dose-response relationship is unclear, tolerance effects on driving are uncertain, different routes of administration (edibles, vaping) have different impairment timelines, and whether medical users are impaired differently from recreational users is unknown..

Simulated driving performance among daily and occasional cannabis users.

Brooks-Russell, Ashley · 2021

Occasional users showed significant increases in lane weaving (SDLP) compared to non-users after smoking (p=0.02, effect size 0.64).

Mechanisms of cannabis impairment: Implications for modeling driving performance.

Burt, Thomas S · 2021

Nearly all driving impairment studies used inhaled cannabis at approximately 6% THC, far below the 20%+ THC flower and 60%+ THC concentrates now sold commercially.

Correlates of driving after cannabis use in high school students.

Cantor, Nathan · 2021

Past-year cannabis-impaired driving prevalence was 10.3%.

Steering clear: Traffic violations among emerging adults who engage in habitual or casual cannabis use.

Ciccarelli, Tiana M · 2021

Both habitual (OR=1.77) and casual (OR=1.79) cannabis users had higher odds of traffic violations than non-users.

Young drivers' determinants of driving under the influence of cannabis: Findings from the Youth Cannabis and Driving Survey (YouCanDS).

Colonna, Robert · 2021

33.3% of respondents reported past DUIC and 42% indicated future DUIC intention.

Duration of Neurocognitive Impairment With Medical Cannabis Use: A Scoping Review.

Eadie, Lauren · 2021

Across all seven included studies, cognitive performance declined mostly in a THC dose-dependent manner with steady resolution in the hours following administration.

Alcohol, marijuana, and nicotine use as predictors of impaired driving and riding with an impaired driver among college students who engage in polysubstance use.

Hultgren, Brittney A · 2021

Compared to alcohol-only users, students using all three substances (alcohol, marijuana, nicotine) had dramatically higher odds of DUI (OR=10.33) and riding with an impaired driver (OR=10.22).

Driving under the influence of cannabis risk perceptions and behaviour: A population-based study in Ontario, Canada.

McDonald, André J · 2021

About 90% of adults agreed DUIC increases collision risk, dropping to 55% among past-year DUIC drivers.

A Digital Health Tool to Understand and Prevent Cannabis-Impaired Driving Among Youth: A Cross-sectional Study of Responses to a Brief Intervention for Cannabis Use.

Moreno, Georgina · 2021

Every 10-point increase in ASSIST score increased the probability of sometimes driving after cannabis use by 7.3%.

Intoxicated driving and riding with impaired drivers: Comparing days with alcohol, marijuana, and simultaneous use.

Patrick, Megan E · 2021

On simultaneous alcohol-marijuana days, odds of riding with an impaired driver were 1.28x higher than alcohol-only days and 2.22x higher than marijuana-only days.

Cannabis and Driving.

Pearlson, Godfrey D · 2021

Cannabis impairs reaction time, lane tracking, and divided attention, though patterns differ from alcohol impairment.

Medicinal cannabis and driving: the intersection of health and road safety policy.

Perkins, Daniel · 2021

Road safety risks associated with medicinal cannabis appear similar to or lower than numerous other potentially impairing prescription medications.

Interventions to Prevent Drugged Driving: A Systematic Review.

Razaghizad, Amir · 2021

Cannabis packaging with health warnings increases knowledge about drugged driving effects (high certainty).

Modeling the system of beliefs that influence driving under the influence of cannabis (DUIC) in Washington State.

Scott, Brandon · 2021

Using structural equation modeling, researchers identified that DUIC behavior was predicted by intention (which had a stronger effect than willingness alone), and both were shaped by control beliefs, attitudes, social norms, and perceptions of people who do or don't drive high..

Assessment of cognitive and psychomotor impairment, subjective effects, and blood THC concentrations following acute administration of oral and vaporized cannabis.

Spindle, Tory R · 2021

High-dose oral and vaporized cannabis impaired cognitive and psychomotor performance, but field sobriety tests showed little sensitivity to cannabis-induced impairment.

Intoxication by a synthetic cannabinoid (JWH-018) causes cognitive and psychomotor impairment in recreational cannabis users.

Theunissen, Eef L · 2021

At 75 microg/kg, JWH-018 impaired motor coordination (CTT), attention (DAT and SST), memory (SMT), lowered speed-accuracy efficiency (MFFT), and slowed response speed.

Drugs and driving prior to cannabis legalization: A 5-year review from DECP (DRE) cases in the province of Quebec, Canada.

Vaillancourt, Lucie · 2021

At least one impairing substance was detected in 98% of the 2,982 Drug Recognition Expert cases.

Association between legalization of recreational cannabis and fatal motor vehicle collisions in the United States: an ecologic study.

Windle, Sarah B · 2021

After adjusting for calendar year, legalization was associated with increased rates of fatal collisions (IRR 1.15, 95% CI 1.06-1.26) and associated deaths (IRR 1.16, 95% CI 1.06-1.27).

Illicit drugs are now more common than alcohol among South Australian crash-involved drivers and riders.

Baldock, Matthew · 2020

Over 15% of crash-involved drivers and motorcyclists tested positive for proscribed drugs (THC, methamphetamine, or MDMA), compared to about 11% of drivers and 5% of motorcyclists with illegal blood alcohol.

Cannabis-related driving and passenger behaviours among high school students: a cross-sectional study using survey data.

Carpino, Melissa · 2020

Greater perceived risk of regular cannabis use was associated with reduced driving under the influence (DUIC) and riding with a cannabis-impaired driver (RWCD) in a dose-response pattern.

Acute Effects of Cannabis Concentrate on Motor Control and Speed: Smartphone-Based Mobile Assessment.

Hitchcock, Leah N · 2020

Arm speed slowed immediately and remained impaired at 1 hour post-use.

Sex differences in driving under the influence of cannabis: The role of medical and recreational cannabis use.

Lloyd, Shawnta L · 2020

Male cannabis users who combined medical and recreational use had the highest probability of DUIC (40%), while female medical-only users had the lowest (20%).

The association between legalization of cannabis use and traffic deaths in Uruguay.

Nazif-Munoz, Jose Ignacio · 2020

Following Uruguay 2013 cannabis legalization, light motor vehicle driver fatality rates showed an immediate 52.4% increase (95% CI 11.6-93.3%, p=0.012).

"Residual blood THC levels in frequent cannabis users after over four hours of abstinence: A systematic review.".

Peng, Yuan Wei · 2020

Across 6 independent studies, frequent cannabis users showed blood THC above 2 ng/mL (or plasma THC above 3 ng/mL) after six days of abstinence in 5 studies.

Occupational Exposure to Secondhand Cannabis Smoke Among Law Enforcement Officers Providing Security at Outdoor Concert Events.

Wiegand, Douglas M · 2020

THC was detected in personal air samples (53-480 ng/m3) and area samples (up to 330 ng/m3).

Cannabidiol (CBD) content in vaporized cannabis does not prevent tetrahydrocannabinol (THC)-induced impairment of driving and cognition.

Arkell, Thomas R · 2019

Both THC-dominant and THC/CBD equivalent cannabis increased lane weaving during simulated driving.

Driving Under the Influence of Cannabis: A Framework for Future Policy.

Chow, Robert M · 2019

Marijuana use is associated with significant cognitive and psychomotor effects.

Are oral fluid testing devices effective for the roadside detection of recent cannabis use? A systematic review.

Dobri, S C D · 2019

Nine oral fluid testing devices were evaluated, and none met the minimum 80% benchmark for sensitivity, specificity, and accuracy set by the ROSITA, ROSITA-2, and DRUID projects.

Marijuana use and driving in Washington State: Risk perceptions and behaviors before and after implementation of retail sales.

Eichelberger, Angela H · 2019

THC-positive daytime drivers increased from 8% before retail sales to 23% six months after.

Strengths and limitations of two cannabis-impaired driving detection methods: a review of the literature.

Ginsburg, Brett C · 2019

Unlike alcohol, THC blood concentrations poorly correspond to amount consumed, crash risk, or degree of impairment.

Effect of Computer-Based Substance Use Screening and Brief Behavioral Counseling vs Usual Care for Youths in Pediatric Primary Care: A Pilot Randomized Clinical Trial.

Knight, John R · 2019

At-risk youth receiving the computer-based screening and brief intervention (CSBI) showed significantly reduced cannabis use (HR 0.62) and reduced riding with impaired drivers (RR 0.58) compared to usual care over 12 months.

Correlation of Breath and Blood Δ9-Tetrahydrocannabinol Concentrations and Release Kinetics Following Controlled Administration of Smoked Cannabis.

Lynch, Kara L · 2019

THC breath concentrations peaked at 15 minutes post-smoking (median 17.8 pg/L) and declined to <5% of peak in all participants by 3 hours.

Developing a phone-based measure of impairment after acute oral ∆9-tetrahydrocannabinol.

Pabon, Elisa · 2019

Across two double-blind studies with oral THC (7.5 and 15 mg), standard computer tasks detected impairment in cognitive speed, reaction time, and working memory.

The utility of delta 9-tetrahydrocannabinol (THC) measures obtained from oral fluid samples in traffic safety.

Romano, Eduardo · 2019

Using data from 7,517 drivers in the National Roadside Survey, oral fluid THC > 0 ng/mL was a good predictor of any blood THC.

Use of Alcohol and Cannabis Among Adults Driving Children in Washington State.

Romano, Eduardo · 2019

Drivers with children were less likely to be alcohol positive (0.2% vs.

Alcohol and marijuana use among young injured drivers in Arizona, 2008-2014.

Shults, Ruth A · 2019

Of drivers with BAC results, 19% tested positive (82% of those at or above 0.08 g/dL).

Marijuana trajectories and associations with driving risk behaviors in Canadian youth.

Sukhawathanakul, Paweena · 2019

Chronic cannabis users and those with increasing use patterns were more likely to engage in risky impaired driving behaviors.

Driver-related risk factors of fatal road traffic crashes associated with alcohol or drug impairment.

Valen, Anja · 2019

THC was found above impairment limits in 4% of fatally injured drivers.

The influence of THC:CBD oromucosal spray on driving ability in patients with multiple sclerosis-related spasticity.

Celius, Elisabeth G · 2018

Researchers reviewed all available evidence on whether Sativex, a THC:CBD mouth spray prescribed for MS-related spasticity, affects driving ability.

Validity of oral fluid test for Delta-9-tetrahydrocannabinol in drivers using the 2013 National Roadside Survey Data.

Jin, Huiyan · 2018

Researchers compared oral fluid and blood THC test results from 4,596 drivers stopped during the 2013 National Roadside Survey. Overall, 8.9% tested positive for THC in oral fluid and 9.4% in blood. Using blood testing as the reference standard, oral fluid testing showed 79.4% sensitivity (correctly identifying positive cases) and 98.3% specificity (correctly identifying negative cases). However, oral fluid THC concentration was a poor predictor of actual blood THC levels.

Marijuana and other substance use among male and female underage drinkers who drive after drinking and ride with those who drive after drinking.

Buckley, Lisa · 2017

In a sample of 2,150 underage drinkers (ages 16-20) from an emergency department, driving after drinking (DD) was reported by 22% of females and 28% of males.

Alcohol or Drug Use and Trauma Recidivism.

Cordovilla-Guardia, Sergio · 2017

Of 1,156 trauma patients (ages 16-70) hospitalized between 2011 and 2015, at least one substance was detected in 45.1%.

Evaluation of divided attention psychophysical task performance and effects on pupil sizes following smoked, vaporized and oral cannabis administration.

Newmeyer, Matthew N · 2017

This controlled study compared impairment from smoked, vaporized, and oral cannabis on standard roadside sobriety tests used in driving under the influence evaluations. For inhaled cannabis (smoked and vaporized), no significant impairment was detected because testing occurred 1.5 and 3.5 hours after dosing, by which time peak effects had subsided. Oral cannabis (edibles) told a different story.

Cannabis and crash responsibility while driving below the alcohol per se legal limit.

Romano, Eduardo · 2017

Analyzing 4,294 drivers involved in fatal crashes in California from 1993-2009, researchers found that cannabis elevated crash responsibility even when alcohol was absent or minimal. At zero blood alcohol concentration (BAC), cannabis-positive drivers had an odds ratio of 1.89 for crash responsibility compared to substance-negative drivers.

Marijuana and the Risk of Fatal Car Crashes: What Can We Learn from FARS and NRS Data?

Romano, Eduardo · 2017

The authors examined why two studies using similar databases and approaches produced opposite conclusions about marijuana's contribution to fatal crash risk.

Cannabinoid disposition in oral fluid after controlled smoked, vaporized, and oral cannabis administration.

Swortwood, Madeleine J · 2017

This controlled study compared oral fluid (saliva) pharmacokinetics after three routes of cannabis administration: smoking, vaporizing, and oral (brownie) consumption. Peak THC in saliva occurred during or immediately after consumption for all routes, driven by direct oral mucosa contamination from inhaled smoke/vapor or the brownie itself.

Cannabis and neuropsychiatry, 1: benefits and risks.

Andrade, Chittaranjan · 2016

This review summarized the evidence on both benefits and risks of cannabis and cannabinoids.

Cannabis and its effects on driving skills.

Bondallaz, Percy · 2016

This review synthesized evidence from laboratory, simulator, on-road, and brain imaging studies to assess how cannabis affects driving performance. Cannabis impaired actual driving by increasing lane weaving and the mean distance to the vehicle ahead.

Drug Recognition Expert (DRE) examination characteristics of cannabis impairment.

Hartman, Rebecca L · 2016

Law enforcement uses the Drug Evaluation and Classification Program (DECP) to assess suspected drug-impaired drivers, but the reliability of specific tests for detecting cannabis impairment has been uncertain.

Techniques and technologies for the bioanalysis of Sativex®, metabolites and related compounds.

Molnar, Anna · 2016

As medical cannabis products like Sativex become more widely prescribed, drug testing faces a growing challenge: how to distinguish legal medical use from illicit recreational use. This review systematically examined methods for detecting THC and CBD across four biological matrices: blood, urine, oral fluid, and hair.

Examination of the role of the combination of alcohol and cannabis in South Australian road crashes.

Baldock, M R J · 2015

Researchers analyzed hospital and forensic data from 1,074 crash-involved drivers and motorcyclists admitted to hospitals in South Australia over three years.

Smoked cannabis' psychomotor and neurocognitive effects in occasional and frequent smokers.

Desrosiers, Nathalie A · 2015

Fourteen frequent cannabis smokers (4+ times per week) and 11 occasional smokers (less than twice per week) smoked a single 6.8% THC cigarette in a controlled setting.

The combined effects of alcohol and cannabis on driving: Impact on crash risk.

Dubois, Sacha · 2015

Researchers examined drivers aged 20+ involved in fatal crashes in the United States from 1991 to 2008 who had been tested for both alcohol and cannabis.

Identifying classes of conjoint alcohol and marijuana use in entering freshmen.

Haas, Amie L · 2015

Researchers used latent profile analysis to identify four distinct groups among 772 incoming college freshmen based on their alcohol and marijuana use patterns.

Roadside drug testing: comparison of two legal approaches in Belgium.

Van der Linden, T · 2015

Belgium changed its roadside drug testing protocol in 2010, moving from urine-based screening to oral fluid-based screening.

Advances in the management of MS spasticity: recent observational studies.

Fernández, Oscar · 2014

This review compiled observational data from post-marketing registries and real-world studies of THC/CBD oromucosal spray (Sativex) for MS spasticity.

Current knowledge on cannabinoids in oral fluid.

Lee, Dayong · 2014

This comprehensive review evaluated the science of oral fluid (saliva) testing for cannabinoids.

The detection of THC, CBD and CBN in the oral fluid of Sativex® patients using two on-site screening tests and LC-MS/MS.

Molnar, Anna · 2014

After Sativex dosing, oral fluid contained very high concentrations of both THC and CBD.

An examination of the validity of the standardized field sobriety test in detecting drug impairment using data from the Drug Evaluation and Classification program.

Porath-Waller, Amy J · 2014

All drug categories, including cannabis, were significantly associated with impaired performance on standardized field sobriety tests.

THC:CBD spray and MS spasticity symptoms: data from latest studies.

Rekand, Tiina · 2014

A randomized, placebo-controlled long-term trial demonstrated that THC:CBD spray (Sativex) was not associated with cognitive decline, depression, or significant mood changes after 12 months of treatment.

Trends in fatal motor vehicle crashes before and after marijuana commercialization in Colorado.

Salomonsen-Sautel, Stacy · 2014

Using federal crash data from 1994 to 2011, researchers found a significant positive trend in the proportion of drivers in fatal crashes who tested positive for marijuana in Colorado after mid-2009, when commercial medical marijuana became widely available.

Alcohol and marijuana use patterns associated with unsafe driving among U.S. high school seniors: high use frequency, concurrent use, and simultaneous use.

Terry-McElrath, Yvonne M · 2014

Analysis of 72,053 high school seniors surveyed from 1976 to 2011 found that higher substance use frequency, particularly alcohol use frequency, was significantly associated with unsafe driving (tickets, warnings, or accidents). Simultaneous use (using alcohol and marijuana at the same time) was associated with the highest rates of unsafe driving, followed by concurrent use (using both substances but at different times), followed by alcohol use alone.

Attention deficit hyperactivity disorder, other mental health problems, substance use, and driving: examination of a population-based, representative canadian sample.

Vingilis, Evelyn · 2014

Of 3,485 licensed drivers surveyed, 3.22% screened positive for ADHD symptoms.

Weed or wheel! FMRI, behavioural, and toxicological investigations of how cannabis smoking affects skills necessary for driving.

Battistella, Giovanni · 2013

Thirty-one male occasional cannabis smokers underwent fMRI while performing a visuo-motor tracking task after smoking cannabis or placebo.

Has the intake of THC by cannabis users changed over the last decade? Evidence of increased exposure by analysis of blood THC concentrations in impaired drivers.

Vindenes, Vigdis · 2013

Researchers analyzed THC blood concentrations from 1,747 drivers apprehended in Norway on suspicion of driving under the influence of cannabis between 2000 and 2010.

A placebo-controlled study to assess Standardized Field Sobriety Tests performance during alcohol and cannabis intoxication in heavy cannabis users and accuracy of point of collection testing devices for detecting THC in oral fluid.

Bosker, W M · 2012

Twenty heavy cannabis users participated in a placebo-controlled study where they smoked cannabis (400 micrograms/kg THC) with or without alcohol.

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, Wendy M · 2012

Twenty-four participants (12 occasional users, 12 heavy users) received dronabinol (10 mg and 20 mg) or placebo in a crossover design, then drove on actual roads.

The prevalence of cannabis-involved driving in California.

Johnson, Mark B · 2012

Researchers collected anonymous oral fluid samples and breath tests from over 900 weekend nighttime drivers across six California jurisdictions.

Adverse effects of cannabis.

· 2011

This comprehensive review examined multiple categories of cannabis adverse effects using systematic methodology. Acute effects included mental slowness, impaired reaction times, and occasionally heightened anxiety.

Cannabinoids in oral fluid following passive exposure to marijuana smoke.

Moore, Christine · 2011

Ten non-marijuana-smoking volunteers spent 3 hours in two Dutch coffee shops where others were actively smoking marijuana.

The effects of cannabis and alcohol on simulated arterial driving: Influences of driving experience and task demand.

Lenné, Michael G · 2010

Twenty-five experienced and 22 inexperienced drivers completed nine simulated driving conditions combining three cannabis doses (placebo, low, high) with three alcohol doses (placebo, low, high). High cannabis doses caused decreased mean speed, increased speed and lateral position variability, increased headways, and longer reaction times.

Conventional and alternative matrices for driving under the influence of cannabis: recent progress and remaining challenges.

Wille, Sarah M R · 2010

The review examined different biological samples used for detecting cannabis in driving-under-the-influence (DUID) cases.

Cognitive and psychomotor effects in males after smoking a combination of tobacco and cannabis containing up to 69 mg delta-9-tetrahydrocannabinol (THC).

Hunault, Claudine C · 2009

Twenty-four non-daily male cannabis users smoked cannabis cigarettes containing 0, 29.3, 49.1, or 69.4 mg THC in a four-way crossover design. Response time slowed linearly across all cognitive tasks (simple reaction time, visual-spatial attention, sustained attention, divided attention, and short-term memory) as THC dose increased.

Neurocognitive performance during acute THC intoxication in heavy and occasional cannabis users.

Ramaekers, J G · 2009

Twelve occasional cannabis users and 12 heavy users smoked THC (500 mcg/kg) or placebo in a double-blind crossover design, with performance tested at intervals over 8 hours. Occasional users showed significant impairment on perceptual motor control (critical tracking), divided attention processing, and motor inhibition (stop signal task) after THC. Heavy users showed no impairment on any task except the stop signal task, where only stop reaction time increased, and only at high blood THC concentrations. Importantly, baseline (sober) performance comparisons between heavy and occasional users showed no persistent performance differences, arguing against residual THC impairment in heavy users. These results demonstrated that cannabis use history strongly determines the behavioral response to a given THC dose..

The effect of cannabis compared with alcohol on driving.

Sewell, R Andrew · 2009

This review compared the driving-related effects of cannabis and alcohol. Both substances impaired driving skills in a dose-related fashion, but the patterns were fundamentally different.

Drug testing in oral fluid.

Drummer, Olaf H · 2006

This review covered a decade of developments in oral fluid drug testing.

Drugs and driving: the Finnish perspective.

Lillsunde, P · 2005

This review examined drug-impaired driving from a Finnish and European perspective.

Passive cannabis smoke exposure and oral fluid testing. II. Two studies of extreme cannabis smoke exposure in a motor vehicle.

Niedbala, R Sam · 2005

Researchers conducted two studies where four non-smoking subjects sat alongside four active cannabis smokers in an unventilated eight-passenger van.

Delta9-tetrahydrocannabivarin as a marker for the ingestion of marijuana versus Marinol: results of a clinical study.

ElSohly, M A · 2001

Because synthetic THC (Marinol) and natural marijuana produce identical urinary metabolites, drug tests cannot tell them apart.

Ethanol, marijuana, and other drug use in 600 drivers killed in single-vehicle crashes in North Carolina, 1978-1981.

Mason, A P · 1984

Researchers tested blood samples from all 600 drivers killed in single-vehicle crashes in North Carolina between 1978 and 1981 for alcohol, THC, barbiturates, cocaine, opiates, phencyclidine, amphetamines, and methaqualone. Alcohol dominated the findings: detected in 79.3% of drivers, with 85.5% of alcohol-positive drivers having blood concentrations at or above 1.0 g/L (substantially above legal limits).

Effects of prescribed medical cannabis and alcohol on real-world driving performance (CAN-TRACK): a study protocol for a two-phase trial.

Arkell, Thomas R · 2026

Study protocol for the first real-world on-track driving study of prescribed medical cannabis patients (n=72 across pain, anxiety, insomnia) compared to alcohol-impaired healthy controls (n=24 at 0.05% BAC), measuring lateral vehicular control..

Cannabis Use in Older Individuals May Be an Important and Under-Recognized Risk Factor for Motor Vehicle Crashes.

Pearlson, Godfrey D · 2026

This paper synthesized evidence on a collision of trends: the growing population of adults over 65 who drive, increasing cannabis use among older adults for medical and recreational purposes, and age-related factors that may amplify cannabis impairment. Older drivers already have more crashes per mile driven and are more likely to be injured or killed in crashes of similar magnitude.

Evaluation of THC-induced neurotoxicity via oxidative stress in undifferentiated SH-SY5Y cells.

Sanz-Pérez, A · 2026

THC at 73.75 and 150 ng/mL significantly reduced cell viability (to 76.5% and 64.6% at 48 hours) and caused morphological changes.

The detection of cannabinoids in breath after ingestion of cannabis-infused edibles.

Bery, Jennifer L · 2025

19 of 29 participants showed a THC concentration peak in breath at 47, 92, or 180 minutes after eating a cannabis edible, while 6 had their highest reading before ingestion and 4 showed no significant change..

Understanding cannabis use and car crashes: Insights from a randomized trial using a driving simulator on THC blood levels and subjective measures of sleepiness and performance.

Cardozo, Bibiana · 2025

In this double-blind crossover RCT (randomized controlled trial where each person receives each condition), inhaled THC increased driving simulator collisions, with the clearest increase observed 4 hours after 10 mg and 30 mg THC.

Using intervention mapping to evaluate 'High-Alert,' a brief smartphone intervention to reduce youth cannabis-impaired driving.

Colonna, Robert · 2025

High Alert, a digital smartphone intervention for youth DUIC, was positively received by participants and showed preliminary efficacy in reducing driving after cannabis co-use compared to a no-contact control.

Bridging THC Knowledge Gaps for Safer Roads: A Call for Action.

Li, Peizhi · 2025

This commentary cuts to the heart of a policy problem: states are setting cannabis driving laws without the science to back them up.

Case Report: Effect of medicinal cannabis on fitness to drive in a patient with Tourette Syndrome and ADHD.

Streetz, Charlotte Marie · 2025

A patient with treatment-resistant Tourette syndrome and ADHD who was prescribed medical cannabis maintained his fitness to drive.

Examining the effect of cannabis cues on cannabis demand in sleep, driving, and typical drug-use contexts.

Miller, Brandon P · 2024

Cannabis picture cues increased self-reported craving (p=.044) but did not significantly alter demand on purchase tasks.

Predicting changes in driving performance in individuals who use cannabis following acute use based on self-reported readiness to drive.

Miller, Ryan · 2024

Can cannabis users tell when they shouldn't drive? This study takes a more granular approach than the French study (RTHC-00093) by examining not just whether self-assessment correlates with impairment, but what factors make self-assessment more or less accurate. Regular cannabis users (at least monthly) were dosed with cannabis containing approximately 6.18% THC, then drove on a simulator at 30, 90, and 180 minutes post-dose.

Feasibility and acceptability of a web-intervention to prevent alcohol and cannabis-impaired driving among adolescents in driver education.

Nameth, Katherine · 2024

In user testing with 8 adolescents, 88% would recommend the tool to a friend and 88% reported learning helpful skills.

Cannabis-based medicines and medical fitness-to-drive: current legal issues in Switzerland.

Palmiere, C · 2024

Since August 2022, Swiss doctors can prescribe cannabis-based medicines without special authorization.

Longitudinal perspectives of riding with a cannabis-impaired driver.

Banz, Barbara C · 2023

Among 105 young adults from a national cohort study, two themes facilitated riding with cannabis-impaired drivers: familiarity with driving context and trust in the driver.

Self-Regulation of Driving Behavior Under the Influence of Cannabis: The Role of Driving Complexity and Driver Vision.

Ortiz-Peregrina, Sonia · 2023

After smoking cannabis, visual acuity and contrast sensitivity were significantly impaired.

A randomized pilot trial of a mobile phone-based brief intervention with personalized feedback and interactive text messaging to reduce driving after cannabis use and riding with a cannabis impaired driver.

Teeters, Jenni B · 2022

College cannabis users in the personalized feedback plus MI-style interactive text messaging condition significantly reduced driving after cannabis use (DACU) and riding with a cannabis-impaired driver (RWCD) over 3 months compared to information control..

Using ecological momentary assessment and a portable device to quantify standard tetrahydrocannabinol units for cannabis flower smoking.

Trull, Timothy J · 2022

One of the biggest problems in cannabis research is that 'a joint' can contain wildly different amounts of THC depending on the flower's potency and how much is used.

The failings of per se limits to detect cannabis-induced driving impairment: Results from a simulated driving study.

Arkell, Thomas R · 2021

At 30 minutes after vaporizing THC, 46% of participants who exceeded legal THC blood limits showed no measurable driving impairment.

Perceived effects of cannabis and changes in driving performance under the influence of cannabis.

Burt, Thomas S · 2021

Subjective cannabis effects predicted changes in driver inputs (steering frequency, reversal rate), while actual driving performance measures like lane weaving were better predicted by dosing condition.

Cognitive and affective responses to marijuana prevention and educational messaging.

Leshner, Glenn · 2021

Driving-themed prevention messages from two different campaigns consistently produced the greatest cognitive resource allocation, highest arousal, and most positive emotional responses, as measured by heart rate, skin conductance, and facial action coding..

Alterations in Electroencephalography Theta as Candidate Biomarkers of Acute Cannabis Intoxication.

Richard, Christian D · 2021

Cannabis intoxication was associated with decreased theta band power (3-5 Hz) during resting state, reduced P400 and late positive potential amplitudes during attention and memory tasks, elevated frontal coherence, and diminished anterior-posterior coherence in the theta band.

A mobile phone-based brief intervention with personalized feedback and interactive text messaging is associated with changes in driving after cannabis use cognitions in a proof-of-concept pilot trial.

Teeters, Jenni B · 2021

Compared to an informational control, participants who received personalized feedback plus interactive text messaging (PFT) showed significantly greater increases in perceived dangerousness of driving after cannabis use at 3-month follow-up, though personalized feedback alone (PF) was not significantly different from control..

Increased Likelihood of Falling in Older Cannabis Users vs. Non-Users.

Workman, Craig D · 2021

Cannabis-using older adults showed higher fall risk scores, poorer one-leg standing balance, and slower gait speed compared to matched non-users.

EEG biomarkers acquired during a short, straight-line simulated drive to predict impairment from cannabis intoxication.

Brown, Timothy L · 2020

Standard deviation of lane position (SDLP) was significantly worse and heart rate elevated during THC sessions compared to placebo.

Recreational cannabis use impairs driving performance in the absence of acute intoxication.

Dahlgren, M Kathryn · 2020

Cannabis users showed increased accidents, speed, lateral movement, and reduced rule-following compared to controls.

Synthetic cannabinoids enhanced ethanol-induced motor impairments through reduction of central glutamate neurotransmission.

Funada, Masahiko · 2020

Synthetic cannabinoids enhanced ethanol-induced motor impairment on a rotarod test.

Effects of Smoking Cannabis on Visual Function and Driving Performance. A Driving-Simulator Based Study.

Ortiz-Peregrina, Sonia · 2020

In 20 young drivers, smoking cannabis significantly worsened visual acuity, contrast sensitivity, and stereoacuity (depth perception).

Exploring perceptions among people who drive after cannabis use: Collision risk, comparative optimism and normative influence.

Wickens, Christine M · 2019

Many participants viewed driving under the influence of cannabis as less risky than driving under alcohol or other drugs.

Impaired Driving Associated with the Synthetic Cannabinoid 5f-Adb.

McCain, K R · 2018

Law enforcement witnessed erratic driving by a 45-year-old male in fall 2017.

JWH-018 impairs sensorimotor functions in mice.

Ossato, A · 2015

Researchers compared the synthetic cannabinoid JWH-018 (found in "Spice" and "herbal blends") with THC across a battery of sensorimotor tests in mice. JWH-018 impaired sensorimotor responses (visual, auditory, tactile) at extremely low doses (0.01-0.1 mg/kg), reduced spontaneous movement at intermediate doses, and caused convulsions, myoclonia, and hyperreflexia at high doses (6 mg/kg). THC at the same doses also reduced some sensorimotor responses but did not inhibit spontaneous locomotion and did not cause any neurological alterations like convulsions.

Detection of drugs of abuse in simultaneously collected oral fluid, urine and blood from Norwegian drug drivers.

Vindenes, V · 2012

Researchers collected blood, urine, and oral fluid simultaneously from 100 suspected drug drivers in Norway.

Factors associated with alcohol and drug use among traffic crash victims in southern Brazil.

De Boni, Raquel · 2011

Emergency room data from two Porto Alegre hospitals over 45 days identified 609 traffic crash victims.

Can the prevalence of high blood drug concentrations in a population be estimated by analysing oral fluid? A study of tetrahydrocannabinol and amphetamine.

Gjerde, Hallvard · 2010

Researchers compared five methods for estimating how many people in a population have high blood THC concentrations based on oral fluid (saliva) testing. The methods ranged from simple calculations (dividing saliva concentration by an average ratio) to complex Monte Carlo simulations. Dividing by the oral fluid/blood regression coefficient gave the best balance of accuracy and precision, making it the recommended method. Monte Carlo simulations could give better accuracy but required good data on the distribution of oral fluid/blood ratios, which is not always available. None of the methods worked well when fewer than 15% of the population had high blood drug concentrations..

Detection of cannabis in oral fluid (saliva) and forehead wipes (sweat) from impaired drivers.

Kintz, P · 2000

Researchers collected blood, urine, saliva, and forehead sweat simultaneously from 198 injured drivers in Strasbourg, France.

Comparative effects of alcohol and marijuana on mood, memory, and performance.

Heishman, S J · 1997

Five male volunteers received three doses each of alcohol and marijuana under double-blind conditions across seven sessions, using technology that controlled puffing and inhalation parameters for precise marijuana dosing. At the highest doses, perceived impairment was identical for alcohol and marijuana.

Cannabinoids in blood and urine after passive inhalation of Cannabis smoke.

Mørland, J · 1985

Five healthy volunteers who had never used cannabis sat in a small closed car (approximately 1,650 liters of air) while other people smoked marijuana or hashish for 30 minutes. Immediately after exposure, THC was detectable in the blood of all five passive smokers at concentrations ranging from 1.3 to 6.3 nanograms per milliliter.

Alcohol and marijuana effects on ocular tracking.

Flom, M C · 1976

Researchers tested experienced substance users on a visual tracking task where participants followed a small moving dot with their eyes.

Effects of intravenous d9-THC on pupillary reaction and pupil size: a prospective, placebo-controlled trial in healthy volunteers not regularly consuming cannabis.

Kleine-Brueggeney, Maren · 2025

Intravenous THC significantly reduced pupillary relative amplitude (from 23.5% to 15.0% at 20 minutes, p = 0.001), constriction time (p = 0.002), and contraction amplitude (p < 0.001) compared to placebo.

Enhancing the Standardized Field Sobriety Test to detect cannabis impairment: An observational study.

Beirness, Douglas J · 2024

Twenty minutes after vaping cannabis (mean THC 6.34 ng/mL), 67% met SFST criteria for suspected impairment.

Is cannabis a slippery slope? Associations between psychological dysfunctioning, other substance use, and impaired driving, in a sample of active cannabis users.

Love, Steven · 2024

Cannabis users were significantly more likely than non-users (n=833 comparison group) to have used other drugs in the past 12 months.

A Latent Variable Analysis of Psychomotor and Neurocognitive Performance After Acute Cannabis Smoking.

Smith, Shelby J · 2023

Factor analysis identified a single latent construct underlying reaction time, decision making, working memory, and spatial-motor performance.