Analysis of US Teen Driving After Using Marijuana, 2017

This cross-sectional study examines the prevalence of and factors associated with driving after using marijuana among US adolescents.


Introduction
Marijuana use impairs cognitive abilities necessary for safe driving, including reaction time, road lane-tracking ability, and attention maintenance. In 2018, 45.3% of US residents aged 12 years or older reported having used marijuana in their lifetime; 10.1% were recent users. 1 Although US high school seniors reporting driving after using marijuana (DAUM) decreased slightly from 14.6% in 2001 to 12.4% in 2011, 2 given recent trends in the legalization of marijuana for recreational and medicinal use, teenagers may show decreases in perceived harmfulness of marijuana use and increases in general marijuana use. 3,4 This study aims to estimate the prevalence of and factors associated with DAUM among US teenaged drivers.

Methods
Cross-sectional survey data were retrieved from the 2017 national Youth Risk Behavior Survey. The Nationwide Children's Hospital institutional review board deemed this study exempt from review and waived informed patient consent because the data did not include personal identifiers. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline.
The outcome was self-reported DAUM at least once in the month before survey completion.
Unlike previous research that estimated DAUM prevalence among all drivers and ignored whether drivers had a history of marijuana use, this study considered 2 denominators: all teen drivers and drivers currently using marijuana, defined as marijuana use at least once in the past month.
Therefore, results are comparable to previous research but also specifically consider behavior of current marijuana users. Crude and adjusted prevalence ratios (PRs) and 95% CIs for DAUM were estimated using Poisson regression with robust variance estimation. Covariate selection was based on literature review and backward selection method (P > .20 removed). Data were weighted to adjust for nonresponse, high school grade, sex, race/ethnicity, and survey design. Statistical significance was set at α = .05 and all tests were 2-tailed. Statistical analysis was performed using Stata version 14.0 (StataCorp) from February to October 2020.

Results
Of the 6816 students aged 14 years or older who responded in 2017 and indicated driving in the past month, 3399 (weighted percentage, 50%) were male, 3027 were White (weighted percentage, 56%), and 969 (weighted percentage, 12.7% [95% CI, 11.3%-14.1%]) reported DAUM in the past month, which was more than twice the rate of reported drinking and driving (327 drivers; weighted percentage, 5%   (Figure).

Discussion
Our study found that almost half (48.8%) of teen drivers who currently use marijuana reported DAUM, which is 17% higher than the rate found in a study of first-year college students in 2012. 5 We also found that the prevalence of DAUM (12.7%) was more than double the prevalence of drinking and driving (5.0%), perhaps reflecting teens' perception that DAUM is less dangerous and more acceptable than driving after using alcohol. Policies such as zero tolerance of THC (tetrahydrocannabinol) while driving and increased age limits for legal marijuana consumption might help alter social norms among teens.
Although we found a higher prevalence of DAUM among male youths than female youths, the differences were not statistically significant. This contrasts with previous research among high school seniors in 2009 to 2012 2 and first-year college students with current marijuana use in 2012. 5 Sex disparities in teen marijuana use are decreasing, 6 and intervention programs should target reduced DAUM among both sexes.
This study had some limitations. We were limited by asking only about DAUM frequency in the past month, and we could not assess a driver's degree of impairment.
As US states legalize medical and recreational marijuana use, teens may misperceive the risk of marijuana use 4 and DAUM. More than 1 in 8 teen drivers reported DAUM in the past month. Almost half of drivers who currently use marijuana engaged in DAUM. Strategies to adopt and enforce policies that change social norms and increase perceived harmfulness offer promise to mitigate the risks associated with DAUM.