Paving the way toward improving safety among drivers with ADHD

Abstract

The ability to drive is important to an individual’s participation in modern society, as it enhances independence and social and economic opportunity. However, motor vehicle crashes are a leading cause of injury-related death in the US—and the leading cause of death among 15- to 24-year olds. Thus, it is critical we sequentially identify who may be at inherently higher crash and why their crash risk might be higher, with the ultimate goal of implementing comprehensive approaches to promote safe driving practices and improve safe mobility.

Several recent well-designed studies, including “Effects of Childhood and Adult Persistent Attention-Deficit/Hyperactivity Disorder on Risk of Motor Vehicle Crashes: Results From the Multimodal Treatment Study of Children With Attention Deficit and Hyperactivity Disorder” by Roy et al. in the current issue,¹ have established that the population of drivers with ADHD are at moderately higher risk of motor vehicle crash involvement and resultant injury.^2–3 By leveraging data from the National Institute of Mental Health’s Longitudinal Multimodal Treatment Study of Children with Attention Deficit and Hyperactivity Disorder (MTA), Roy et al. make a timely methodological contribution by highlighting the importance of assessing ADHD status and symptoms concurrently with crash risk, rather than relying on past diagnosis or symptomology. The study found that the rate of crash involvement among 220 participants who met DSM-5 criteria as an adult (termed “persisters”) was an estimated 1.46 times as high as the rate among 221 participants who no longer met criteria in adulthood (“desisters”). As a substantial proportion of individuals who had ADHD as a child do not meet diagnostic criteria as adults, targeting a population of individuals with ADHD based solely on their diagnostic status as children may provide a limited understanding of adverse driving outcomes among adult drivers with a history of this condition.

As future research continues to refine our understanding of the specific subgroups of ADHD drivers at particularly high risk, it will be important to ensure that studies include adequate specificity in the operationalization of both ADHD status and driving outcomes. With regard to ADHD status, it should be noted that Roy et al.’s study was limited to a clinically-referred sample of individuals diagnosed with ADHD, Combined presentation in childhood; those with the Inattentive presentation were not included. Future studies should aim to include all ADHD presentations and more inclusive epidemiologic samples, as individuals with ADHD are typically managed in the primary care setting. In addition, although Roy et al. was able to control for a range of demographic factors, time since licensure, and several important co-occurring conditions, they were not able to effectively capture ADHD medication use. As sample size allows, future studies should aim to understand whether and how co-occurring factors and medication use modify crash risk. It would also be interesting to know if potential protective factors (e.g., parental involvement; school engagement) serve to reduce risk.

With regard to measuring driving outcomes, advancing knowledge on this issue will require that studies of crash risk move beyond self-reported crash involvement as a primary outcome variable. This definition includes minor crashes and “fender benders”, which are of much less public health importance than more serious injury crashes. Further, there is a high potential for underestimated reports of crashes (i.e., positive illusory bias).⁴ One way to overcome these biases is to leverage the vast amounts of objective driving-related data that states already collect via police crash reports, driver licensing data, and traffic citation databases. Linkage of study data to these existing administrative databases is not a trivial process, but is well worth the effort.

It is also time to uncover why crash risk is elevated among drivers with ADHD. Comprehensively addressing this critical question will require that we move beyond secondary analyses of survey data or analyses of existing administrative data sources. Prospective studies specifically designed to address the issue of driving with ADHD are needed, and should work to identify both modifiable distal and proximal (in-vehicle) risk factors. Further, even within the immediate crash environment, rarely if ever is there a single “cause” of crash, but a chain of successive cause-effect events that ultimately results in a crash.⁵ Capitalizing on novel methods such as in-vehicle naturalistic driving technology will be able to provide important insight on behaviors and actions occurring in the moments just before a crash. Finally, given the complexity of the issues of both ADHD and traffic safety, advancing knowledge will benefit from transdisciplinary teams with collective expertise in both fields, as well as partnership between researchers, advocates, community groups that support these individuals (e.g., healthcare providers, driver educators), and parents and youth themselves. We see this as a critical component—and one of the most rewarding aspects—of our own collaborative work on this issue.

Given both the high rates of ADHD and the heightened crash risk among these drivers—in particular the youngest drivers—it is critical to develop and implement interventions to encourage safe driving even before we fully uncover causal mechanisms for these crashes. Well-known safe driving practices should be strongly encouraged; these include family adoption of optimal Graduated Driver Licensing provisions at home regardless of age at licensure, buckling up on every drive, not driving while impaired, and ensuring that novice young drivers with ADHD are in the safest vehicles their families can afford in order to mitigate injury if they were to crash. This may seem obvious. However, the rate of alcohol-related crashes and citations is 2–3 times as high among young drivers with ADHD compared with their non-ADHD counterparts,² suggesting that long-standing driving safety messages are not entirely resonating with this population. We should also consider adapting interventions that have shown effectiveness among adolescents with ADHD (e.g., skill training approaches) to the driving context, as well as tailoring evidence-based young driver training interventions (e.g., hazard anticipation) to those with ADHD. Finally, promising and emerging approaches require further development and testing, including enlisting clinicians to assess readiness to drive and standardizing approaches used by certified driving rehabilitation specialists.

Importantly, there is a concerning indication that we are failing to engage youth in approaches that are likely to be helpful. For example, use of ADHD medication has been shown to reduce crash risk among drivers with ADHD;⁶ however, few adolescents with ADHD are medicated at the time of licensure and adherence with medication among older adolescents with ADHD is generally poor.^7–8 Although ongoing monitoring of driver readiness and performance by an adolescent’s primary care provider is a promising approach, findings from our recent study suggest that discussion about driver readiness between adolescents with ADHD and their primary care provider are negligible.⁹ It is critically important that we seize every opportunity to apply well-established and promising approaches to improve driving safety among drivers with ADHD—even as our understanding of why crash risk is higher is still developing—to ensure we are doing all we can to keep drivers with ADHD safe on the road.