Estimating Cannabis Involvement in Fatal Crashes in Washington State Before and After the Legalization of Recreational Cannabis Consumption Using Multiple Imputation of Missing Values

Road safety implications of the partial legalisation of cannabis in Germany: protocol for a quasi-experimental study

INTRODUCTION

Germany is reforming its legal approach to cannabis, allowing the possession and cultivation of cannabis for recreational purposes. The objective of this study is to investigate the impact of the policy reform on (1) The prevalence of cannabis use in the general population and (2) Driving under the influence of cannabis (DUIC) among regular users.

METHODS AND ANALYSIS

A quasi-experimental research design will be employed, with repeated cross-sectional surveys on self-reported DUIC and cannabis use conducted at three measurement points in Germany (intervention group) and Austria (control group) over a 2-year observation period (2023-2025). Data will be collected from approximately 50 000 individuals aged between 18 years and 64 years. To minimise reporting biases in the measurement of DUIC, we will use direct and indirect assessments via crosswise model and motor vehicle accident data from official statistics. In a difference-in-difference framework, regression analyses and interrupted time series analysis will be carried out for hypothesis testing.

ETHICS AND DISSEMINATION

Participants will be informed about voluntary participation, data protection laws and the option to delete data on request. Ethical approval was obtained from the Local Psychological Ethics Committee of the Centre for Psychosocial Medicine in Hamburg, Germany (reference number: 0686). Findings will be disseminated through scientific networks and will be key for a comprehensive evaluation of the cannabis law reform. The findings will facilitate the design and implementation of road safety measures.

Estimating Drug Involvement in Fatal Overdoses With Incomplete Information

INTRODUCTION

Death certificates provide incomplete information on the specific drug categories involved in fatal overdoses. The accuracy of previously developed corrections for this and modifications to them was examined. Uncorrected mortality rates were compared with rates from the preferred correction models.

METHODS

Data were obtained for the universe of 932,364 drug overdoses in the U.S. between 1999 and 2020, including 769,982 (82.6%) with a drug classification and 162,382 (17.4%) without, from the National Center for Health Statistics Multiple Cause of Death files. Opioid and cocaine involvement for unclassified overdoses were estimated using multiple approaches. Prediction accuracy was assessed as the mean absolute deviation between actual and estimated involvement for a test sample with known drug involvement. Corrected death rates from preferred models were compared with uncorrected rates. Analyses were conducted in 2022-2023.

RESULTS

Previous regression-based corrections that controlled for decedent characteristics can be improved upon by adding state-fixed effects as covariates. Once this is done, supplementary controls for county characteristics or contributory causes of death do not materially improve prediction accuracy. Properly designed naïve models, which distribute unspecified drug deaths proportionately to specified deaths, often provide similar results and, for county-level analyses, supply the most accurate predictions. Uncorrected results substantially understate the levels of opioid and cocaine involvement and can either understate or overstate changes over time.

CONCLUSIONS

Failing to correct for incomplete information on death certificates leads to inaccurate counts of deaths from specific categories of drugs, such as opioids. However, relatively simple corrections are available that substantially improve accuracy.

Collisions and cannabis: Measuring the effect of recreational marijuana legalization on traffic crashes in Washington State

OBJECTIVE

Washington State was among the first states in the US to legalize recreational consumption and retail sales of marijuana. Recreational use of cannabis was legalized December 6, 2012, following the passage of Initiative 502 30 days prior. Roughly 19 months later the first retail cannabis stores opened their doors for public sales ("commercialization"). I measure the impact of cannabis legalization and commercialization on traffic collisions in Washington State.

METHODS

With county-level vehicle crash data from the Washington State Department of Transportation collected monthly, I utilize an interrupted time-series framework with Poisson estimation to compare traffic collisions with recreational retail cannabis sales revenue from 2011 (three years pre-commercialization) through 2017 (three years post-commercialization). First, I measure the shift in collisions brought about by Washington's 2012 cannabis legalization. Then, I compare retail cannabis sales-a measure of commercialization-to traffic collisions based on severity of injury (fatal, severe injury, minor injury, non-injury, and all).

RESULTS

After controlling for confounding factors, evidence suggests that recreational cannabis legalization led to fewer fatal and serious injury collisions. Retail cannabis sales generally correlate with more traffic collisions, particularly for less severe (minor injury) crashes. These findings are robust to the inclusion of additional control variables pertaining to county-level cannabis usage and driving behavior while intoxicated.

CONCLUSIONS

Cannabis legalization led to fewer fatal, serious, and minor injury collisions. Commercialization (cannabis sales) correlated with an increase in less severe crashes. Although cannabis use generally increased in Washington State following legalization/commercialization, survey data suggest that driving behavior while under the influence of cannabis did not change significantly over the post-commercialization period. Future research should focus on measuring the dose-dependent impact of cannabis consumption on traffic collisions. This should include recognition of the importance of cannabis dosing, timing, and route of consumption. Lastly, the dangers of poly-drug driving-particularly cannabis and alcohol-are well established and should be high priority for further research.

Effects of Cannabis Legalization on Road Safety: A Literature Review

BACKGROUND

Legalizing medical and recreational cannabis and decriminalizing this substance may have unanticipated effects on traffic safety. The present study aimed to assess the impact of cannabis legalization on traffic accidents.

METHODS

A systematic review was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) declaration of the articles included in the Web of Science (WoS) and Scopus databases. The number of papers included in the review was 29.

RESULTS

The results show that in 15 papers, there is a relationship between the legalization of medical and/or recreational cannabis and the number of traffic accidents, while in 5 papers, no such relationship is observed. In addition, nine articles indicate a greater number of risk behaviors related to driving after consumption, identifying young, male, and alcohol consumption together with cannabis as the risk profile.

CONCLUSIONS

It can be concluded that the legalization of medical and/or recreational cannabis has negative effects on road safety when considering the number of jobs that affect the number of fatalities.

Developments and Changes in Primary Public Health Outcome Indicators Associated with the Legalization of Non-Medical Cannabis Use and Supply in Canada (2018): A Comprehensive Overview

Canada legalized non-medical cannabis use and supply for adults in 2018. We examined developments and changes associated with the legalization policy reform on key indicators for public health, namely cannabis (including frequent/problematic) use prevalence, cannabis-related hospitalizations, cannabis-impaired driving, and cannabis sourcing. We identified peer-reviewed and "grey" study data that featured population-level or other quasi-representative samples and comparable outcome data for pre- and post-legalization periods, including possible trends of changes over time. Cannabis use has increased in select population groups, with use modes shifting away from smoking. Evidence on cannabis-related hospitalizations (e.g., for mental health) is mixed. The prevalence of cannabis-impaired driving appears to be generally steady but THC exposure among crash-involved drivers may have increased. Increasing proportions of users obtain cannabis products from legal sources but some-especially regular-users continue to use illicit sources. Overall, data suggest a mixed and inconclusive picture on cannabis legalization's impacts on essential public health indicators, including select extensions in trends from pre-legalization.

Influence of cannabis use history on the impact of acute cannabis smoking on simulated driving performance during a distraction task

Objective: This research explores the driving performance of people who use cannabis daily or occasionally during distraction tasks performed following acute cannabis use.Methods: Healthy adults aged 25 to 45 years with different cannabis usage histories were recruited to participate in a within-subjects controlled experiment using a car-based driving simulator. Participants were classified as having daily use (n = 31), occasional use (1 or 2 times per week; n = 24), or no-use (n = 30). Participants completed a practice drive followed by four 5-10 minute driving scenarios during the baseline period. Participants then smoked self-procured cannabis flower ad libitum for up to 15 minutes. Thirty minutes later, they completed four additional 5-10 minute scenarios. Scenarios were paired according to difficulty and randomized across the baseline and post-use periods. Each scenario contained between 0 and 3 repetitions of a distraction task where the participant was prompted by an audio message to select an app from a 4 × 5 grid displayed on a mounted tablet, a step that would require briefly looking away from the roadway. Measures of driving performance (lane departures, standard deviation of lateral position) were assessed during the five-second period following the audio trigger and analyzed using generalized linear mixed models.Results: Those with a pattern of occasional use were significantly more likely to experience a lane departure during distraction periods after acute cannabis use relative to baseline (OR = 3.71, p = 0.04, CI = 1.04, 13.17), while those with daily use did not exhibit a similar increase (OR = 1.56, p = 0.43, CI = 0.52, 4.64). Changes in departure risk were significantly greater for the occasional use group compared to no-use (p = 0.02), but not for the daily use group compared to no-use (p = 0.18). However, following acute use, those who use daily exhibited decreases in speed relative to baseline in comparison to the changes observed in the no-use group (p = 0.02), while differences between occasional and no-use did not reach statistical significance (p = 0.052). Differences in standard deviation of lateral position were not statistically significant, likely due to the short duration of tasks.Conclusions: These results find the largest potential safety concerns associated with a pattern of occasional use, who displayed an increase in lane departures after acute cannabis smoking. Those in the daily use group decreased their speed, which may be interpreted as compensation for drug effects. Further research is needed to understand the effects during longer and more complex secondary tasks.

A systematic review of factors associated with illegal drug driving

Drug driving is a serious problem worldwide that can increase the risk of road crashes. This systematic review seeks to identify factors associated with drug driving (i.e., driving after consuming drugs other than alcohol) to highlight gaps in existing knowledge and inform the design of more effective countermeasures. A search of the literature was conducted for the period January 1, 2005 to July 31, 2021 using six different databases. The search protocol followed PRISMA guidelines and was registered in PROSPERO (#CRD42021234616). Studies that met inclusion criteria compared drug drivers with either non-drug drivers, alcohol-only drivers or drug drivers from an earlier time period, to identify factors specifically associated with drug driving, rather than common to all drivers. Two hundred and nineteen publications met the inclusion criteria and were included within the review. Based on the findings, a logic model was developed that presents the factors associated with drug driving. Various sociodemographic, psychosocial and legal factors emerged as the main factors associated with illegal drug driving. At the sociodemographic and psychological levels, drug drivers were more likely to be single, young males who often drive after using cannabis and who score high on sensation-seeking and impulsivity scales. The key social factor found to be associated with drug driving was peer acceptance/disapproval of the behaviour. At the legal level, the review suggested that the effectiveness of current enforcement approaches to drug driving vary among jurisdictions around the world due to differences in the level of perceived certainty of apprehension and the chances of punishment avoidance. Future research into the anticipated and actual rewards for drug driving is needed to inform the development of more effective countermeasures.