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

BACKGROUND

The objective of this study was to examine the relationship between cannabis and alcohol use and occurrence of motor vehicle collision (MVC) among patients in the emergency department (ED).

METHODS

This was a cross-sectional study of visits to EDs in Denver, CO, Portland, OR, and Sacramento, CA by drivers who were involved in MVCs and presented with injuries (cases) and non-injured drivers (controls) who presented for medical care. We obtained blood samples and measured delta-9-THC and its metabolites. Alcohol levels were determined by breathalyzer or samples taken in the course of clinical care. Participants completed a research-assistant-administered interview consisting of questions about drug and alcohol use prior to their visit, context of use, and past-year drug and alcohol use. Multiple logistic regression was used to estimate the association between MVC and cannabis/alcohol use, adjusted for demographic characteristics. We then stratified participants based on levels of cannabis use and calculated the odds of MVC across these levels, first using self-report and then using blood levels for delta-9-THC in separate models. We conducted a case-crossover analysis, using 7-day look-back data to allow each participant to serve as their own control. Sensitivity analyses examined the influence of usual use patterns and driving in a closed (car, truck, van) versus open (motorcycle, motorbike, all-terrain vehicle) vehicle.

RESULTS

Cannabis alone was not associated with higher odds of MVC, while acute alcohol use alone, and combined use of alcohol and cannabis were both independently associated with higher odds of MVC. Stratifying by level of self-reported or measured cannabis use, higher levels were not associated with higher odds for MVC, with or without co-use of alcohol; in fact, high self-reported acute cannabis use was associated with lower odds of MVC (odds ratio [OR] 0.18, 95% confidence interval [CI] 0.05-0.65). In the case-crossover analysis, alcohol use alone or in combination with cannabis was associated with higher odds of MVC, while cannabis use alone was again associated with decreased odds of MVC.

CONCLUSIONS

Alcohol use alone or in conjunction with cannabis was consistently associated with higer odds for MVC. However, the relationship between measured levels of cannabis and MVC was not as clear. Emphasis on actual driving behaviors and clinical signs of intoxication to determine driving under the influence has the strongest rationale.

Increased identification of cannabis use among drivers involved in motor vehicle collisions using an expanded cannabis inventory

OBJECTIVES

The objectives of this study were to implement and examine the potential capture rate of a novel instrument, the Expanded Cannabis Inventory, in a population of emergency department (ED) patients presenting after motor vehicle collisions (MVC).

METHODS

Study participants who presented to the ED after MVC were recruited from three hospitals in cannabis-legal states (Denver, CO; Portland, OR; and Sacramento, CA). Research assistants (RAs) administered the Expanded Cannabis Inventory, which includes a wide variety of products that have become readily available in states where cannabis is legal, in addition to assessments related to patient demographic characteristics, general health, cannabis attitudes, and dependency measures. RAs also obtained blood samples for delta-9-THC and metabolites.

RESULTS

Among 692 participants who provided responses to questions about cannabis use, 292 (42%) reported past-year use. Seventy-eight (27%) of those identified as using cannabis were only captured due to items in the expanded instrument. These patients were more likely to be White and were more likely to perceive daily use to be of high risk. Fewer had Cannabis Use Disorder Inventory Test (CUDIT) scores consistent with hazardous cannabis use. However, more of the patients only captured by the expanded instrument had high measured blood levels of delta-9-THC on samples obtained in the ED.

CONCLUSIONS

Changing cannabis use patterns must be reflected in our measurements for clinical practice, research, and surveillance. Instruments that are the current standard in clinical practice capture limited data and may no longer perform well enough to identify a complete cohort or to provide insight into the health behaviors of patients.

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

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A national survey sampled current cannabis users.

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Users in medical cannabis states were less likely to report driving high.

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Users in recreational states were less likely to report driving high.

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Likelihood of driving high varied by frequency of cannabis use.

The relationship between cannabis legalization and traffic safety remains unclear. Physiological measures of cannabis impairment remain imperfect. This analysis used self-report data to examine the relationship between cannabis legalization and driving under the influence of cannabis (DUIC)1.

Using a cross-sectional national sample (2016–2017) of 1,249 past–30-day cannabis users, we regressed self-reported DUIC (driving within three hours of “getting high”) on cannabis legalization (recreational and medical (recreational), medical only (medical), or no legal cannabis), adjusting for demographics, days of use (past 30 days), days of use*legal status, calibration weights, and geographic clustering.

The risk of DUIC in recreational (risk ratio [RR] = 0.41, 95% confidence interval (CI):0.23–0.72) and medical (RR = 0.39, 95% CI:0.20–0.79) states was lower than in states without legal cannabis, with one exception. Among frequent cannabis users (≥20 days per month), there was a significantly lower risk of DUIC for those living in recreational states (RR = 0.70, 95% CI: 0.49–0.99), but not for those living in medical states (RR = 0.87, 95% CI: 0.60–1.24), compared to users living in states without legal cannabis.

The risk of self-reported DUIC was lower in recreational and medical cannabis states compared to states without legal cannabis. The only exception was for frequent users in medical states, for whom there was no difference in risk compared to frequent users living in states without legal cannabis.

Cannabis presentations to the emergency department after MVC in the era of legalization for recreational use

INTRODUCTION

The objectives of this study were to examine cannabis and alcohol use among injured patients presenting to emergency departments (ED) in cannabis-legal states to capture an expanded profile of cannabis use and evaluate differences in motor-vehicle collision (MVC) characteristics among those using cannabis alone and in combination with alcohol.

METHODS

This was a cross-sectional study of ED visits by drivers in MVC who presented to one of three study sites. Event-related and usual drug and alcohol use information were obtained using a detailed interviewer-administered computerized questionnaire. We also obtained data from blood and breathalyzer tests and the electronic medical record. We examined frequency and types of acute and past-year cannabis and alcohol use and crash mechanisms and characteristics. Our primary method of determining substance use was self-report; we used biosamples secondarily.

RESULTS

Eight percent of drivers reported cannabis use in the 8 h prior to MVC, alone or in combination with alcohol; however, a higher proportion (18%) were positive by biosample. High-risk crash features were common in MVCs associated with cannabis, as they were for alcohol use and co-use of cannabis and alcohol; however, patients injured seriously enough to require admission were less likely to report cannabis use (7% vs. 9%) and more likely to report alcohol use (16% vs. 10%).

CONCLUSIONS

Cannabis use was common among patients presenting after MVC in this sample of cannabis-legal states. Practical Applications: Differences between self-report and biosample data for cannabis and alcohol use were significant and supports the need to use both means of assessing acute use.