In asking about cannabis use, an expanded instrument was used to capture a wide variety of use beyond common forms that are the focus of traditional instruments but may miss the wide variety of products that have become readily available in states where cannabis is legal. For example, asking specifically about hash reveals some cannabis use that would be missed by asking about marijuana alone. We also measured cannabis dependence with the Cannabis Use DisorderI dentification Test.Research assistants abstracted information from the electronic health records, including documented crash characteristics, disposition,and bio-samples obtained for clinical use, using a standardized data form. Given that scene fatalities would not be transported to the hospital,this study has inherent selection bias towards less severe MVCs. The Portland site was the only one to recruit 24/7 , so the overnight shift, which may see more trauma and substance use, may be relatively under sampled. Recruitment of drivers in collisions may have created a bias in reporting of cannabis use due to fear of legal or medical consequences, as discussed above. Acute use within an 8-hour period does not necessarily translate to impairment. There may have been other factors,including unmeasured con-founders, contributing to crash occurrence.Choosing thresholds of time for the window in which we decided to inquire about drug and alcohol use was subjective and required trade-offs.
For example, for alcohol use, if we chose a short window, we might exclude those with heavy alcohol use but would be more likely to capture drinking that impacted driving; if we chose a longer window, mobile grow system we would capture those with heavy use but might also capture those whose alcohol use was low to moderate and no longer an influence on their driving. In this study of drivers in MVCs presenting to the EDs of three cities where cannabis is legal for recreational use, several observations are notable. First, self-reported use in the period prior to the MVC was relatively low, while bio-samples suggested a much higher rate of acute use. Second, usual past-year use and cannabis dependence was high compared to prior ED studies and compared to national samples. Many high-risk crash features were common in MVCs associated with cannabis, as they werefor alcohol use and co-use of cannabis and alcohol; however, while patients requiring admission were less likely to report cannabis use, they were more likely to report alcohol use, suggesting there may have been cannabis-related driving behaviors that contributed to MVCs but mitigated against more serious harms.The prevalence of past-year use in this study population was higher than reported in national samples and previous ED reports but concordant with more recent observations of increasing national rates of cannabis use, particularly in states with legal medical and recreational marijuana use .
EDs continue to be an important place to capture epidemiologic trends in drug and alcohol use and individuals at high risk for health consequences from substance use.In our previous work , we have used self-report as the standard for drug and alcohol use, as it has demonstrated concordance with objective measures in a variety of settings . Therefore, we chose self-report a priori as the primary criteria for substance use. However, mobile vertical rack in the current study, we found a large difference between rates of use as divulged by self-report and acute use suggested by bio-samples. The bio-sample might have detected cannabis use that fell outside of the 8-hour window during which we felt use was most likely to influence driving. Further,there is likely variability in the accuracy of the cannabis levels depending on the route of use and variable absorption times . However, when asked about past-year use,which would not carry as much social or legal implication, particularly in a cannabis legal state, respondents reported high levels of use, suggesting a potential bias in our capture of acute use.An additional explanation for the difference between self-reported and bio-samples might be the specific circumstances of the study: we asked about drug use in relation to an MVC, in which drivers might be concerned about the legal implications of divulging information related to their culpability in the event, despite the increasing normalization of drug use, and drug use reporting,over time . Among racial and ethnic groups in particular, individuals may reasonably fear harsher assessments of culpability and sentencing , Lack of earned trust of the medical establishment among racial minority populations likely also played a role.Study participants may have been reluctant to report drug use due to social desirability bias and concerns of how such information may impact their clinical care.