THC likely reduces speed and reaction time in young drivers, but high-quality evidence is limited
A systematic review found moderate confidence that THC reduces mean speed, headway distance, and reaction time while increasing lane and steering variability in young drivers aged 15-24.
Quick Facts
What This Study Found
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. The overall level of confidence was moderate (Level B). The review found a lack of Class I studies and insufficient attention to sex/gender differences and representative samples.
Key Numbers
Systematic review of studies on drivers ages 15-24. Class II evidence (Level B, moderate confidence). THC effects: reduced mean speed, reduced headway distance, reduced reaction time, increased lane variability, increased steering variability.
How They Did This
Systematic review registered in PROSPERO, searching 7 databases. Quality of evidence assessed using an established classification system (Class I-IV for study quality, Level A-U for confidence). Focused specifically on drivers ages 15-24.
Why This Research Matters
Young drivers already face the highest crash risk. Understanding the specific ways cannabis impairs their driving can inform targeted education and prevention rather than relying on generalizations from adult studies.
The Bigger Picture
As cannabis legalization expands, young drivers may face increased exposure. The evidence gaps identified here, particularly regarding sex differences and realistic dosing, need to be addressed to develop effective impairment standards.
What This Study Doesn't Tell Us
Limited number of high-quality studies focused specifically on youth. Most driving performance studies use simulator environments that may not reflect real-world conditions. Sex and gender effects are understudied. Dose-response relationships unclear.
Questions This Raises
- ?How do cannabis effects on young driver performance compare to alcohol effects?
- ?Does the duration of impairment differ in younger versus older drivers?
- ?Would roadside testing protocols need to be adjusted for the specific impairment patterns seen in youth?
Trust & Context
- Key Stat:
- Moderate confidence that THC impairs multiple driving performance measures in youth
- Evidence Grade:
- Systematic review with structured evidence grading, but limited by the small number of high-quality youth-specific studies available.
- Study Age:
- 2021 systematic review. Identifies significant evidence gaps in understanding cannabis effects on young driver performance.
- Original Title:
- Young and under the influence: A systematic literature review of the impact of cannabis on the driving performance of youth.
- Published In:
- Accident; analysis and prevention, 151, 105961 (2021)
- Authors:
- Alvarez, Liliana(4), Colonna, Robert(4), Kim, Sean, Chen, Caron, Chippure, Katherine, Grewal, Jasleen, Kimm, Chris, Randell, Travis, Leung, Victoria
- Database ID:
- RTHC-02958
Evidence Hierarchy
Analyzes all available research on a topic using a structured method.
What do these levels mean? →Frequently Asked Questions
How does cannabis affect young drivers specifically?
THC likely reduces mean speed, headway distance, and reaction time while increasing lane and steering variability. However, the confidence level is moderate because few high-quality studies focus specifically on drivers ages 15-24.
Is driving on cannabis as dangerous as driving drunk?
This review did not directly compare cannabis to alcohol impairment. It focused on characterizing the specific ways THC affects young driver performance, which involves different impairment patterns than alcohol.
Read More on RethinkTHC
- 420-sober-survival-guide
- CBT-cannabis-recovery
- cannabis-relapse-cycle-pattern
- cold-turkey-vs-taper-quit-weed
- dating-sober-after-quitting-weed
- exercise-quitting-weed-anxiety-brain
- grieving-quitting-weed-loss
- help-someone-quit-weed
- how-to-quit-weed
- journaling-weed-withdrawal
- marijuana-anonymous-SMART-recovery-compare
- meditation-mindfulness-weed-withdrawal
- partner-still-smokes-weed
- partner-still-smokes-weed-quitting
- pink-cloud-sobriety-cannabis
- quit-weed-cold-turkey
- quit-weed-or-cut-back-which-is-better
- quit-weed-regret-went-back
- quitting-weed-20s
- quitting-weed-30s
- quitting-weed-after-years
- quitting-weed-during-crisis-divorce-job-loss
- quitting-weed-exercise
- quitting-weed-grief-loss-coping
- quitting-weed-legal-state
- quitting-weed-success-stories
- quitting-weed-triggers-environment
- relapsed-smoking-weed-what-to-do
- relapsed-weed
- should-i-quit-weed
- sober-music-festival-concert-without-weed
- supplements-weed-withdrawal
- telling-friends-quitting-weed
- weed-relapse-prevention-plan
- weed-relapse-why-it-happens
- weed-ritual-replacement
- weed-ruined-relationships
- weed-social-media-triggers-quit
Cite This Study
https://rethinkthc.com/research/RTHC-02958APA
Alvarez, Liliana; Colonna, Robert; Kim, Sean; Chen, Caron; Chippure, Katherine; Grewal, Jasleen; Kimm, Chris; Randell, Travis; Leung, Victoria. (2021). Young and under the influence: A systematic literature review of the impact of cannabis on the driving performance of youth.. Accident; analysis and prevention, 151, 105961. https://doi.org/10.1016/j.aap.2020.105961
MLA
Alvarez, Liliana, et al. "Young and under the influence: A systematic literature review of the impact of cannabis on the driving performance of youth.." Accident; analysis and prevention, 2021. https://doi.org/10.1016/j.aap.2020.105961
RethinkTHC
RethinkTHC Research Database. "Young and under the influence: A systematic literature revie..." RTHC-02958. Retrieved from https://rethinkthc.com/research/alvarez-2021-young-and-under-the
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.