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Cannabis and Impaired Driving

Cannabis and Impaired Driving Impaired driving is a major cause of preventable death worldwide. Alcohol-impaired driving accounted for a mean of 19% (range, 3%-34%) of the motor vehicle crash deaths in 20 countries in 20161; in 2018, 29% of the 36 560 crash deaths in the US were attributed to impaired driving.2By comparison, driving under the influence of cannabis was estimated to account for 8700 road traffic deaths worldwide in 2013.3 Alcohol and cannabis are often consumed together, and their combined use is associated with greater crash risk than the use of either substance alone.3 Notably, cannabinoids are the most commonly detected other drugs (besides alcohol) in fatally injured drivers (up to 15% in urban areas), and the prevalence is increasing.4,5 Understanding and addressing cannabis-impaired driving has challenges that differ from alcohol-impaired driving. Cannabis is not limited to a single drug. Recreational cannabis generally contains both Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), among dozens of other cannabinoids. The best evidence for beneficial effects of cannabinoids are for the use of CBD to treat rare pediatric convulsive disorders.6 A National Academy of Sciences panel cited substantial evidence for modest effects of cannabinoids for chronic pain, nausea and vomiting associated with chemotherapy, and spasticity of multiple sclerosis.7 However, cannabinoids used for the treatment of disorders and their symptoms are largely pharmaceutical-grade products (ie, not smoked or vaped products) that contain synthetic THC or combinations of THC and CBD. The majority of cannabis products available and used are not specific pharmaceutically prepared cannabinoids in well-studied doses, and dose labels often misrepresent actual contents. Thus, assessing cannabis exposure is complex. Furthermore, unlike alcohol, cannabinoid level does not correspond to performance impairment or perceived intoxication, which may persist long after peak levels can be measured. In addition, when cannabinoids are detected in drivers involved in fatal crashes, other drugs are often also detected. Consumption of THC, which produces short-term intoxication and positive mood,8 has been demonstrated in laboratory studies to impair motor performance and cognitive function required for safe driving.3 The effects of CBD, of THC combined with CBD, of cannabinoids with other substances, and the effects of multiple daily doses or repeated long-term cannabinoid use on driving performance are less well-studied. In this issue of JAMA, a crossover clinical trial by Arkell and colleagues9 tested whether consumption of specific doses of THC and CBD resulted in driving impairment, as measured by standard deviation of lateral position (SDLP) assessed during on-road driving under experimental conditions. In this trial, which enrolled 26 healthy participants with occasional cannabis use, SDLP (a measure of lane weaving, swerving, and overcorrecting) was increased by THC-dominant cannabis (+2.33 cm [95% CI, 0.80 to 3.86]; P < .001) and THC/CBD-equivalent cannabis (+2.83 cm [95% CI, 1.28 to 4.39]; P < .001), but not CBD-dominant cannabis (−0.05 cm [95% CI, −1.49 to 1.39]; P > .99) when compared with placebo. To obtain these data, participants were instructed to drive in the middle of the right traffic lane, allowing approximately 1 meter of road surface on either side of the vehicle. The mean SDLP was calculated by summing deviations in lateral position over the time of the driving test; the mean range of lateral position values in this study was approximately 50 cm. The investigators concluded that consumption of the tested samples of cannabis that contained THC, whether the samples also contained CBD or not, resulted in impaired driving as measured under the study conditions. Consumption of CBD-dominant cannabis did not impair driving in this study, but the authors acknowledged that the doses tested may not represent common usage and the effect size for CBD-dominant cannabis may not have excluded clinically important impairment. A post hoc analysis provided additional evidence that driving performance was not impaired by the dose of CBD administered in the trial. Drivers in the CBD condition were no more likely to show driving impairment than driving improvement compared with placebo at SDLP thresholds corresponding with blood alcohol concentrations of 0.05% (the legal limit for driving in most industrialized countries) or 0.02% (the blood alcohol concentration at which crash risk has clearly been shown to increase).10 However, it is likely that many patients and consumers are exposed to doses of CBD that are higher than the dose tested in this study. It is also likely that participants in the study by Arkell et al,9 who reported occasional cannabis use, are not representative of populations that use medicinal CBD or regularly use recreational cannabis. Moreover, the doses of cannabinoids in the study may not be typical. Participants in the trial by Arkell et al9 received 13.75 mg of CBD prior to driving. These participants are not likely representative of people who use medicinal CBD or regularly use recreational cannabis. Participants in the trial by Arkell et al9 received 13.75 mg of CBD prior to driving. This dose is lower than the 20-mg/kg dose of CBD administered for the control of seizures in children and young adults with Dravet syndrome6 and corresponds with the lower end of the range of concentrations of CBD (0.10 mg/mL-655.27 mg/mL) observed in a sample of CBD extracts sold online.11 Although there are too few studies on which to base dosing of CBD, and therefore no authoritative source, social media and other posted recommendations include doses of 600 mg per day,12 and a recent phase 2 study of CBD to treat cannabis use disorder suggested efficacy for 800 mg daily,13 well above the 14-mg dose tested by Arkell et al.9 The effects of common doses of CBD, the effects of cannabinoids with other substances (although THC is known to have additive effects with alcohol), and the effects of multiple daily doses or repeated long-term cannabinoid use on driving impairment are unknown, although the study by Arkell et al9 represents a rigorous and important attempt to answer these challenging questions. While the findings from this trial do not support the conclusion that it is safe to drive after consuming CBD, it is clear that THC did impair driving performance and that the effects of THC were not limited to just 1 driving task. Consumption of THC and THC/CBD adversely affected performance on standardized tests of processing speed, divided attention, psychomotor function, working memory, decision making, and cognitive flexibility. Drivers who consumed THC were generally aware that their driving was impaired, although participants reported that consumption of THC/CBD was associated with less anxiety, reduced strength of drug effects, and greater confidence to drive than THC alone. These findings challenge the myth that CBD ameliorates the psychoactive/psychomotor effects of THC. Further study is needed involving people who use cannabis regularly, of duration of cannabinoid effects at varied doses, and of driving performance and other cognitive tasks at the full range of CBD doses consumed by the general population, with or without a specific medical recommendation. Clinicians should caution their patients that cannabis products containing equal parts CBD and THC are no less impairing than products containing THC alone. Moreover, given that alcohol is a major preventable cause of motor vehicle crash deaths and risk is additive with cannabis, patients should be advised to avoid any drinking, particularly with cannabis use, before driving. Back to top Article Information Corresponding Author: Thomas B. Cole, MD, MPH, 105 Misty Pines Pl, Carrboro, NC 27510 (tbcole@bellsouth.net). Conflict of Interest Disclosures: Dr Saitz reported receipt of grants from the National Institutes of Health (NIH) during the conduct of the study; grants from NIH, the National Institute on Alcohol Abuse and Alcoholism, the National Institute on Drug Abuse, Philadelphia College of Osteopathic Medicine, and the Burroughs Wellcome Fund outside the submitted work; nonfinancial support from Alkermes; personal fees from the American Society of Addiction Medicine, the American Medical Association, the National Council on Behavioral Healthcare, Kasier Permanente, UpToDate/Wolters Kluwer, Yale University, the National Committee on Quality Assurance, University of Oregon, Oregon Health Sciences University, RAND Corporation, Leed Management Consulting/Harvard Medical School, Partners, Beth Israel/Deaconess Hospital, the American Academy of Addiction Psychiatry, the Group Health Cooperative, Smart Recovery, the Institute for Research and Training in the Addictions, Charles University, Prague, Brandeis University, the Massachusetts Medical Society, and personal fees for serving as a medical malpractice expert witness outside the submitted work; other (travel) from the International Network on Brief Interventions for Alcohol and Other Drugs (INEBRIA; supported via funds from Systembolaget), Karolinska Institutet, the Institute for Research and Training in the Addictions, and Charles University, Prague; President, International Society of Addiction Journal Editors; research consulting to ABT Corporation (not remunerated), editor of a book published by Springer, editorial board of the Journal of Addictive Diseases and Addiction Science and Clinical Practice and Substance Abuse. No other disclosures were reported. References 1. Sauber-Schatz EK, Ederer DJ, Dellinger AM, Baldwin GT. Vital signs: motor vehicle injury prevention—United States and 19 comparison countries.  MMWR Morb Mortal Wkly Rep. 2016;65(26):672-677. doi:10.15585/mmwr.mm6526e1PubMedGoogle ScholarCrossref 2. US Department of Transportation; National Highway Traffic Safety Administration’s National Center for Statistics and Analysis. Traffic Safety Facts Research Note. 2018 Fatal motor vehicle crashes: overview. Report No. DOT HS 812 826. Published October 2019. Accessed November 10, 2020. https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/812826 3. Ramaekers JG. Driving under the influence of cannabis: an increasing public health concern.  JAMA. 2018;319(14):1433-1434. doi:10.1001/jama.2018.1334PubMedGoogle ScholarCrossref 4. Berning A, Compton R, Wochinger K,; US Department of Transportation; National Highway Traffic Safety Administration’s Office of Behavioral Safety Research. Traffic Safety Facts Research Note. Results of the 2013–2014 National Roadside Survey of Alcohol and Drug Use by Drivers. Report No. DOT HS 812 118. Published February 2015. Accessed November 10, 2020. https://www.nhtsa.gov/sites/nhtsa.dot.gov/files/812118-roadside_survey_2014.pdf 5. Azagba S, Shan L, Latham K. Rural-urban differences in cannabis detected in fatally injured drivers in the United States.  Prev Med. 2020;132:105975. doi:10.1016/j.ypmed.2019.105975PubMedGoogle Scholar 6. Hill KP. Medical use of cannabis in 2019.  JAMA. 2019;322(10):974-975. doi:10.1001/jama.2019.11868PubMedGoogle ScholarCrossref 7. National Academies of Sciences, Engineering and Medicine (NASEM). The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research. National Academies Press; 2017. 8. Bidwell LC, Ellingson JM, Karoly HC, et al. Association of naturalistic administration of cannabis flower and concentrates with intoxication and impairment.  JAMA Psychiatry. 2020;77(8):787-796. doi:10.1001/jamapsychiatry.2020.0927PubMedGoogle ScholarCrossref 9. Arkell TR, Vinckenbosch F, Kevin RC, Theunissen EL, McGregor IS, Ramaekers JG. Effect of cannabidiol and Δ9-tetrahydrocannabinol on driving performance: a randomized clinical trial.  JAMA. Published December 1, 2020. doi:10.1001/jama.2020.21218Google Scholar 10. Naimi TS, Xuan Z, Sarda V, et al. Association of state alcohol policies with alcohol-related motor vehicle crash fatalities among US adults.  JAMA Intern Med. 2018;178(7):894-901. doi:10.1001/jamainternmed.2018.1406PubMedGoogle ScholarCrossref 11. Bonn-Miller MO, Loflin MJE, Thomas BF, Marcu JP, Hyke T, Vandrey R. Labeling accuracy of cannabidiol extracts sold online.  JAMA. 2017;318(17):1708-1709. doi:10.1001/jama.2017.11909PubMedGoogle ScholarCrossref 12. Caporuscio J. Medical News Today website. What is the correct dosage of CBD? Published January 17, 2020. Accessed November 10, 2020. https://www.medicalnewstoday.com/articles/327518#research 13. Freeman TP, Hindocha C, Baio G, et al. Cannabidiol for the treatment of cannabis use disorder: a phase 2a, double-blind, placebo-controlled, randomised, adaptive Bayesian trial.  Lancet Psychiatry. 2020;7(10):865-874. doi:10.1016/S2215-0366(20)30290-XPubMedGoogle ScholarCrossref http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png JAMA American Medical Association

Cannabis and Impaired Driving

Cole, Thomas B.; Saitz, Richard
JAMA , Volume 324 (21) – Dec 1, 2020
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References (10)

Publisher
American Medical Association
Copyright
Copyright 2020 American Medical Association. All Rights Reserved.
ISSN
0098-7484
eISSN
1538-3598
DOI
10.1001/jama.2020.18544
Publisher site
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Abstract

Impaired driving is a major cause of preventable death worldwide. Alcohol-impaired driving accounted for a mean of 19% (range, 3%-34%) of the motor vehicle crash deaths in 20 countries in 20161; in 2018, 29% of the 36 560 crash deaths in the US were attributed to impaired driving.2By comparison, driving under the influence of cannabis was estimated to account for 8700 road traffic deaths worldwide in 2013.3 Alcohol and cannabis are often consumed together, and their combined use is associated with greater crash risk than the use of either substance alone.3 Notably, cannabinoids are the most commonly detected other drugs (besides alcohol) in fatally injured drivers (up to 15% in urban areas), and the prevalence is increasing.4,5 Understanding and addressing cannabis-impaired driving has challenges that differ from alcohol-impaired driving. Cannabis is not limited to a single drug. Recreational cannabis generally contains both Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), among dozens of other cannabinoids. The best evidence for beneficial effects of cannabinoids are for the use of CBD to treat rare pediatric convulsive disorders.6 A National Academy of Sciences panel cited substantial evidence for modest effects of cannabinoids for chronic pain, nausea and vomiting associated with chemotherapy, and spasticity of multiple sclerosis.7 However, cannabinoids used for the treatment of disorders and their symptoms are largely pharmaceutical-grade products (ie, not smoked or vaped products) that contain synthetic THC or combinations of THC and CBD. The majority of cannabis products available and used are not specific pharmaceutically prepared cannabinoids in well-studied doses, and dose labels often misrepresent actual contents. Thus, assessing cannabis exposure is complex. Furthermore, unlike alcohol, cannabinoid level does not correspond to performance impairment or perceived intoxication, which may persist long after peak levels can be measured. In addition, when cannabinoids are detected in drivers involved in fatal crashes, other drugs are often also detected. Consumption of THC, which produces short-term intoxication and positive mood,8 has been demonstrated in laboratory studies to impair motor performance and cognitive function required for safe driving.3 The effects of CBD, of THC combined with CBD, of cannabinoids with other substances, and the effects of multiple daily doses or repeated long-term cannabinoid use on driving performance are less well-studied. In this issue of JAMA, a crossover clinical trial by Arkell and colleagues9 tested whether consumption of specific doses of THC and CBD resulted in driving impairment, as measured by standard deviation of lateral position (SDLP) assessed during on-road driving under experimental conditions. In this trial, which enrolled 26 healthy participants with occasional cannabis use, SDLP (a measure of lane weaving, swerving, and overcorrecting) was increased by THC-dominant cannabis (+2.33 cm [95% CI, 0.80 to 3.86]; P < .001) and THC/CBD-equivalent cannabis (+2.83 cm [95% CI, 1.28 to 4.39]; P < .001), but not CBD-dominant cannabis (−0.05 cm [95% CI, −1.49 to 1.39]; P > .99) when compared with placebo. To obtain these data, participants were instructed to drive in the middle of the right traffic lane, allowing approximately 1 meter of road surface on either side of the vehicle. The mean SDLP was calculated by summing deviations in lateral position over the time of the driving test; the mean range of lateral position values in this study was approximately 50 cm. The investigators concluded that consumption of the tested samples of cannabis that contained THC, whether the samples also contained CBD or not, resulted in impaired driving as measured under the study conditions. Consumption of CBD-dominant cannabis did not impair driving in this study, but the authors acknowledged that the doses tested may not represent common usage and the effect size for CBD-dominant cannabis may not have excluded clinically important impairment. A post hoc analysis provided additional evidence that driving performance was not impaired by the dose of CBD administered in the trial. Drivers in the CBD condition were no more likely to show driving impairment than driving improvement compared with placebo at SDLP thresholds corresponding with blood alcohol concentrations of 0.05% (the legal limit for driving in most industrialized countries) or 0.02% (the blood alcohol concentration at which crash risk has clearly been shown to increase).10 However, it is likely that many patients and consumers are exposed to doses of CBD that are higher than the dose tested in this study. It is also likely that participants in the study by Arkell et al,9 who reported occasional cannabis use, are not representative of populations that use medicinal CBD or regularly use recreational cannabis. Moreover, the doses of cannabinoids in the study may not be typical. Participants in the trial by Arkell et al9 received 13.75 mg of CBD prior to driving. These participants are not likely representative of people who use medicinal CBD or regularly use recreational cannabis. Participants in the trial by Arkell et al9 received 13.75 mg of CBD prior to driving. This dose is lower than the 20-mg/kg dose of CBD administered for the control of seizures in children and young adults with Dravet syndrome6 and corresponds with the lower end of the range of concentrations of CBD (0.10 mg/mL-655.27 mg/mL) observed in a sample of CBD extracts sold online.11 Although there are too few studies on which to base dosing of CBD, and therefore no authoritative source, social media and other posted recommendations include doses of 600 mg per day,12 and a recent phase 2 study of CBD to treat cannabis use disorder suggested efficacy for 800 mg daily,13 well above the 14-mg dose tested by Arkell et al.9 The effects of common doses of CBD, the effects of cannabinoids with other substances (although THC is known to have additive effects with alcohol), and the effects of multiple daily doses or repeated long-term cannabinoid use on driving impairment are unknown, although the study by Arkell et al9 represents a rigorous and important attempt to answer these challenging questions. While the findings from this trial do not support the conclusion that it is safe to drive after consuming CBD, it is clear that THC did impair driving performance and that the effects of THC were not limited to just 1 driving task. Consumption of THC and THC/CBD adversely affected performance on standardized tests of processing speed, divided attention, psychomotor function, working memory, decision making, and cognitive flexibility. Drivers who consumed THC were generally aware that their driving was impaired, although participants reported that consumption of THC/CBD was associated with less anxiety, reduced strength of drug effects, and greater confidence to drive than THC alone. These findings challenge the myth that CBD ameliorates the psychoactive/psychomotor effects of THC. Further study is needed involving people who use cannabis regularly, of duration of cannabinoid effects at varied doses, and of driving performance and other cognitive tasks at the full range of CBD doses consumed by the general population, with or without a specific medical recommendation. Clinicians should caution their patients that cannabis products containing equal parts CBD and THC are no less impairing than products containing THC alone. Moreover, given that alcohol is a major preventable cause of motor vehicle crash deaths and risk is additive with cannabis, patients should be advised to avoid any drinking, particularly with cannabis use, before driving. Back to top Article Information Corresponding Author: Thomas B. Cole, MD, MPH, 105 Misty Pines Pl, Carrboro, NC 27510 (tbcole@bellsouth.net). Conflict of Interest Disclosures: Dr Saitz reported receipt of grants from the National Institutes of Health (NIH) during the conduct of the study; grants from NIH, the National Institute on Alcohol Abuse and Alcoholism, the National Institute on Drug Abuse, Philadelphia College of Osteopathic Medicine, and the Burroughs Wellcome Fund outside the submitted work; nonfinancial support from Alkermes; personal fees from the American Society of Addiction Medicine, the American Medical Association, the National Council on Behavioral Healthcare, Kasier Permanente, UpToDate/Wolters Kluwer, Yale University, the National Committee on Quality Assurance, University of Oregon, Oregon Health Sciences University, RAND Corporation, Leed Management Consulting/Harvard Medical School, Partners, Beth Israel/Deaconess Hospital, the American Academy of Addiction Psychiatry, the Group Health Cooperative, Smart Recovery, the Institute for Research and Training in the Addictions, Charles University, Prague, Brandeis University, the Massachusetts Medical Society, and personal fees for serving as a medical malpractice expert witness outside the submitted work; other (travel) from the International Network on Brief Interventions for Alcohol and Other Drugs (INEBRIA; supported via funds from Systembolaget), Karolinska Institutet, the Institute for Research and Training in the Addictions, and Charles University, Prague; President, International Society of Addiction Journal Editors; research consulting to ABT Corporation (not remunerated), editor of a book published by Springer, editorial board of the Journal of Addictive Diseases and Addiction Science and Clinical Practice and Substance Abuse. No other disclosures were reported. References 1. Sauber-Schatz EK, Ederer DJ, Dellinger AM, Baldwin GT. Vital signs: motor vehicle injury prevention—United States and 19 comparison countries.  MMWR Morb Mortal Wkly Rep. 2016;65(26):672-677. doi:10.15585/mmwr.mm6526e1PubMedGoogle ScholarCrossref 2. US Department of Transportation; National Highway Traffic Safety Administration’s National Center for Statistics and Analysis. Traffic Safety Facts Research Note. 2018 Fatal motor vehicle crashes: overview. Report No. DOT HS 812 826. Published October 2019. Accessed November 10, 2020. https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/812826 3. Ramaekers JG. Driving under the influence of cannabis: an increasing public health concern.  JAMA. 2018;319(14):1433-1434. doi:10.1001/jama.2018.1334PubMedGoogle ScholarCrossref 4. Berning A, Compton R, Wochinger K,; US Department of Transportation; National Highway Traffic Safety Administration’s Office of Behavioral Safety Research. Traffic Safety Facts Research Note. Results of the 2013–2014 National Roadside Survey of Alcohol and Drug Use by Drivers. Report No. DOT HS 812 118. Published February 2015. Accessed November 10, 2020. https://www.nhtsa.gov/sites/nhtsa.dot.gov/files/812118-roadside_survey_2014.pdf 5. Azagba S, Shan L, Latham K. Rural-urban differences in cannabis detected in fatally injured drivers in the United States.  Prev Med. 2020;132:105975. doi:10.1016/j.ypmed.2019.105975PubMedGoogle Scholar 6. Hill KP. Medical use of cannabis in 2019.  JAMA. 2019;322(10):974-975. doi:10.1001/jama.2019.11868PubMedGoogle ScholarCrossref 7. National Academies of Sciences, Engineering and Medicine (NASEM). The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research. National Academies Press; 2017. 8. Bidwell LC, Ellingson JM, Karoly HC, et al. Association of naturalistic administration of cannabis flower and concentrates with intoxication and impairment.  JAMA Psychiatry. 2020;77(8):787-796. doi:10.1001/jamapsychiatry.2020.0927PubMedGoogle ScholarCrossref 9. Arkell TR, Vinckenbosch F, Kevin RC, Theunissen EL, McGregor IS, Ramaekers JG. Effect of cannabidiol and Δ9-tetrahydrocannabinol on driving performance: a randomized clinical trial.  JAMA. Published December 1, 2020. doi:10.1001/jama.2020.21218Google Scholar 10. Naimi TS, Xuan Z, Sarda V, et al. Association of state alcohol policies with alcohol-related motor vehicle crash fatalities among US adults.  JAMA Intern Med. 2018;178(7):894-901. doi:10.1001/jamainternmed.2018.1406PubMedGoogle ScholarCrossref 11. Bonn-Miller MO, Loflin MJE, Thomas BF, Marcu JP, Hyke T, Vandrey R. Labeling accuracy of cannabidiol extracts sold online.  JAMA. 2017;318(17):1708-1709. doi:10.1001/jama.2017.11909PubMedGoogle ScholarCrossref 12. Caporuscio J. Medical News Today website. What is the correct dosage of CBD? Published January 17, 2020. Accessed November 10, 2020. https://www.medicalnewstoday.com/articles/327518#research 13. Freeman TP, Hindocha C, Baio G, et al. Cannabidiol for the treatment of cannabis use disorder: a phase 2a, double-blind, placebo-controlled, randomised, adaptive Bayesian trial.  Lancet Psychiatry. 2020;7(10):865-874. doi:10.1016/S2215-0366(20)30290-XPubMedGoogle ScholarCrossref

Journal

JAMA – American Medical Association

Published: Dec 1, 2020

Keywords: cannabis,marijuana

There are no references for this article.