When ADHD inattention, impulsivity, and distractibility get behind the wheel, serious risk of accidents and injury skyrocket. Within the first month of driving, teens with ADHD are 62% more likely than their non-ADHD peers to be involved in an automobile crash. Over the first four years of having a license, drivers with ADHD are 37% more likely to get into a crash, twice as likely to drive while intoxicated, and 150% more likely to receive an alcohol, drug, or moving violation compared to their non-ADHD peers.1
In short, study after study shows that ADHD is a significant risk factor while operating a motor vehicle — and that is a serious public health issue.
The good news: Research also clearly indicates that ADHD medication greatly improves driving performance. But there’s still more to be done to understand the underlying reasons and mechanisms for risky driving, and the interventions that enhance safety. Sensitive, high-tech driving simulators, which allow us to observe behaviors behind the wheel, are proving essential for continued research in a safe environment. But they do little good if clinicians don’t communicate to patients — especially to teenagers and young adults — the risks associated with ADHD and driving, and the importance of taking medication to improve driving safety.
ADHD and Driving: What Behaviors Increase Risk?
Driving is a multidimensional activity, involving many cognitive abilities and executive functions. The underlying impairments inherent to ADHD – including inattention, impulsivity, and difficulty concentrating and resisting distractions – are thought to interfere with driving and contribute to adverse outcomes.2 But research has yet to fully answer the question of just how ADHD impairs driving, and which susceptibilities specifically lead to problems on the road.
[Get This Free Download: What Are Your Teen’s Weakest Executive Functions?]
Still, there’s no doubt that ADHD is associated with adverse driving outcomes, as shown by the following findings replicated across multiple studies:
- Compared to drivers without ADHD, significantly more drivers with ADHD
- drive without a license
- have a license revoked or suspended
- have multiple crashes
- have multiple traffic citations, especially for speeding.3
- Drivers with ADHD are more likely than drivers without ADHD to rate themselves poorly on driving habits.3
- Drivers with ADHD are more likely than drivers without ADHD to be legally at fault for traffic incidents.4
- Drivers with ADHD experience more severe crashes and are more likely to be killed in a car crash than drivers without ADHD.5 6
- Adolescents, more than any other age group, are at a high risk for motor vehicle crashes.7 Within this group, teen drivers with ADHD are at a greater risk than their non-ADHD peers of crashing.1 8
ADHD and Driving: Are Safety Risks Treatable?
The Road to Better Research
Research indicates that ADHD medication – stimulants in particular – may improve driving safety and mitigate risk for drivers with ADHD.
We first learned of the potential benefits of stimulant medication on drivers with ADHD from early studies involving driving simulations and self-reports.9 Though informative, the results of these initial studies were difficult to interpret, given limited information on the validity of the driving simulators used and the usefulness of some outcome variables chosen for these studies. It was difficult to ascertain from these studies what improvement in driving actually meant or entailed. Also unclear from these studies was the extent to which the proven clinical effects of ADHD medication would generalize to driving impairments.
A Refined Driving Simulator
In a joint effort between researchers from Massachusetts General Hospital (MGH) and Massachusetts Institute of Technology (MIT), we developed and validated a driving simulator to assess the aspects of ADHD that could account for driving impairments.10 The simulation – done in a real vehicle with a virtual roadway projected on a large, single screen – tests driving under various environments (urban, rural, highway), under differing stimulus intensity (active and monotonous), and while performing other tasks (e.g., driving while having a cellphone conversation).
[Read: Stop Distracted Driving with These Safety Tips]
Our simulator validation studies showed that drivers with ADHD were more likely than controls to crash into a surprise obstacle while driving under a monotonous, low-stimulus condition for an extended period.10 This finding supports the idea that inattention is a key moderator of impaired driving in ADHD, and that individuals with ADHD have difficulties remaining alert while driving without stimulation. Simulator studies also show, as indicated in self-assessments, that drivers with ADHD are more likely than drivers without ADHD to speed, to pass and weave through traffic, and to get into accidents.11
ADHD Medication and Driving
With a validated simulator, we next assessed the effects of a stimulant (lisdexamfetamine) on driving performance in young adults with ADHD versus a placebo.12 We tested young adults specifically because this group, as we know, is at the highest risk for driving accidents and infractions in general.
In our study, participants drove twice through a 43-mile virtual roadway of varying stimulus conditions and environments. The second simulation, unlike the first, featured five surprise events (including the appearance of cyber dogs and oncoming vehicles). Analysis showed that the medicated group reacted faster to these surprise events – 9.1% faster, on average – than did the placebo group.12 Furthermore, during the surprise events, drivers in the medicated group were 67% less likely to have a collision than were drivers in the placebo group.12
What does that mean in the real world? Assuming a driving speed of 65 mph, the reaction time translates to 131 feet and 120 feet for the unmedicated and medicated group, respectively. The additional 11 feet that an unmedicated driver travels could translate to serious, even deadly consequences.
These results suggest that lisdexamfetamine, which we could extrapolate to stimulants, may be useful in clinical practice to help reduce driving risks facing young adults with ADHD. These findings – that medication improves driving performance in individuals with ADHD – have been replicated across other studies as well.6
Despite discernible differences in driving performance between medicated and unmedicated drivers, it is important to note that we did not see any association between clinical improvement in ADHD symptoms and driving simulation outcomes in our 2012 study. In other words, lisdexamfetamine was associated with faster reaction time and a lower likelihood of having a collision independently of the clinical effects of ADHD medication. What this means is that we cannot assume that a medication that provides benefits in ADHD symptoms will also provide benefits in driving outright. We need to specifically test the effect of ADHD medication during driving to study its potential benefits.
ADHD and Driving: Clinical Implications
Given what we know about ADHD and driving, and the benefits of medication on driving performance, it is critical for clinicians to educate patients and their families – especially if a patient is a teen or a young adult – about the importance of safe driving.
In my practice, I do not try to discourage anybody from driving. Instead, I have discussions with patients who are just beginning to drive about the seriousness of having a deadly weapon at their control, the meaning of safe driving, and the importance of being medicated – for ADHD in general and while driving. For families that stop ADHD treatment on weekends and during “downtime,” I emphasize the importance of driving only while medication is active. Patients and families must consider driving time relative to when medication is taken. A short-acting medication taken about half an hour before hitting the road may just be life-saving.
ADHD and Driving: Conclusions
From traffic citations to serious crashes, drivers with ADHD – especially if unmedicated – are more likely than drivers without ADHD to experience adverse driving outcomes. Researchers are still trying to understand the specific aspects of ADHD that contribute to unsafe driving, though it is likely that symptoms of inattention, like mind wandering and difficulty sustaining focus, are important factors. Validated simulators are useful for studying driving behaviors in this population and continue to be refined to model a realistic driving experience and improve the quality of research.
Many studies, including ours, show that stimulants reduce driving risk and improve safety for individuals with ADHD – findings that carry major public health relevance, considering the high risk of crashes associated with the condition. In practice – and as we continue to study just how medication improves driving behaviors – clinicians must educate young patients and their families about the risks, and of the importance of driving while on medication.
ADHD and Driving: Next Steps
- Read: My Brother Died in a Car Crash Because of His ADHD
- Download: Boost Your Teen’s Executive Functions
- Read: How to Steer Your Teen Toward Safe Driving
- Read: “I’m Too Distracted When I Drive”
The content for this article was derived with permission from “The Effects of Lisdexamfetamine Dimesylate on the Driving Performance of Young Adults with ADHD,” presented by Joseph Biederman, M.D., at the APSARD 2022 Annual Conference.
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