Accidents & Violence, Aging, Author Interviews, Cannabis, JAMA / 19.01.2024
Even older, regular users of cannabis should refrain from driving after cannabis use
MedicalResearch.com Interview with:
[caption id="attachment_61266" align="alignleft" width="150"]
Dr. Di Ciano[/caption]
Patricia Di Ciano, PhD
Scientist, Institute for Mental Health Policy Research, Centre for Addiction and Mental Health
Assistant Professor, Department of Pharmacology and Toxicology
University of Toronto
Campbell Family Mental Health Research Institute
Collaborative Program in Neuroscience
MedicalResearch.com: What is the background for this study?
Response: It is now fairly well established that cannabis has a detrimental effect on driving. The most consistently reported effect of cannabis on driving is to increase ‘weaving’ on the road. We know that cannabis use is on the rise in people over 65 years of age. In fact, over the past few years cannabis use is increasing the most in this age group.
Despite this, there are few studies of the effects of cannabis on people over 65; most studies have been conducted on younger adults. We know that there are important age-related changes in the way the body works that may alter the impact of cannabis on the body. Also, older adults may have more experience with cannabis and this can change the effects of cannabis.
Dr. Di Ciano[/caption]
Patricia Di Ciano, PhD
Scientist, Institute for Mental Health Policy Research, Centre for Addiction and Mental Health
Assistant Professor, Department of Pharmacology and Toxicology
University of Toronto
Campbell Family Mental Health Research Institute
Collaborative Program in Neuroscience
MedicalResearch.com: What is the background for this study?
Response: It is now fairly well established that cannabis has a detrimental effect on driving. The most consistently reported effect of cannabis on driving is to increase ‘weaving’ on the road. We know that cannabis use is on the rise in people over 65 years of age. In fact, over the past few years cannabis use is increasing the most in this age group.
Despite this, there are few studies of the effects of cannabis on people over 65; most studies have been conducted on younger adults. We know that there are important age-related changes in the way the body works that may alter the impact of cannabis on the body. Also, older adults may have more experience with cannabis and this can change the effects of cannabis.
Dr. Potter[/caption]
MedicalResearch.com Interview with:
Kelly Potter, PhD, RN, CNE
T32 Postdoctoral Scholar
CRISMA Center, Department of Critical Care Medicine
University of Pittsburgh
MedicalResearch.com: What is the background for this study?
Response: While it is well-recognized that survivors of critical illness often experience persistent problems with mental, cognitive, and physical health, very little is known about how these problems (collectively known as post-intensive care syndrome (PICS)) affect resumption of meaningful activities, such as driving.
Sarah Windle[/caption]
Sarah Windle, MPH
PhD Student in Epidemiology
Department of Epidemiology, Biostatistics, and Occupational Health
McGill University (Montréal, Québec, Canada)
MedicalResearch.com: What is the background for this study?
Response: Concerns have been raised about the potential for increases in impaired driving following the legalization of recreational cannabis use in Canada in October 2018. Data from Statistics Canada suggest that cannabis use in the previous three months increased among adults (15 and older) from 14% before legalization in 2018 to 17% in 2019. Among those users with a driver’s license, 13% reported driving within two hours of cannabis use. While this proportion remained the same before and after legalization, this indicates that the absolute number of individuals who reported driving within two hours of use has increased following legalization (due to an increase in the number of users).

Prof. Kleiman[/caption]
Prof. Mark A. R. Kleiman PhD
Affiliated Faculty, NYU Wagner; Professor of Public Policy
NYU Marron Institute of Urban Management
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: As state after state legalizes the sale of cannabis, the question of cannabis-impaired driving is getting more attention. There is evidence that the practice has become more common, both because cannabis use - and especially heavy, frequent use - has increased and because a distressingly large fraction of cannabis users believe, falsely, that stoned driving is safe.
The natural response to the problem is to treat cannabis on a par with alcohol: fairly severe criminal penalties for impaired driving, with impairment defined by a specific level of the drug in the body. The paper argues that this would be a mistake, for four independent reasons:
- While cannabis makes driving riskier, it does so by about a factor of two, with no strongly observed dependency on dosage. Alcohol, by contrast, has a steep dose-effect curve. At the legal limit of 0.08% blood alcohol content by weight, the relative risk of drunk driving is at least eight; at 0.15%, which is fairly common, the relative risk has been estimated at 30-50. So there is no justification for punishing stoned driving as severely as we punish drunk driving.
- The lack of evidence of a strong dose-effect relationship suggests that a legal standard based on the content of cannabinoids in blood may not be appropriate.
- Even if a blood standard were valid, the lack of a breath test would make enforcing that standard nearly impossible as a practical matter.
- The long and unpredictable course of cannabis metabolism means that frequent users will be at risk of failing a drug test even when they are neither subjectively intoxicated nor objectively impaired. Worse, they would have no way of judging in advance whether or not driving would be legal. The result would be a re-criminalization of cannabis use through the back door.





