Drive safely! Adults with ADHD keep crashing their vehicles

By Mario Louza[1]

The paper by Roy et al. (2020) calls our attention to the high rate of motor vehicle crashes in adults with persistent symptoms of ADHD. Car accidents are an important cause of death and disability, and this population is particularly exposed, due to innatention and impulsivity.

Roy A, Garner AA, Epstein JN, Hoza B, Nichols JQ, Molina BSG, Swanson JM, Arnold LE, Hechtman L. 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/Hyperactivity Disorder. J Am Acad Child Adolesc Psychiatry. 2020 Aug;59(8):952-963. doi: 10.1016/j.jaac.2019.08.007.

Objective: To determine motor vehicle crash (MVC) risk in adults with a history of childhood attention-deficit/hyperactivity disorder (ADHD) and persistent ADHD symptoms.

Method: Participants with (n = 441) and without (n = 239; local normative comparison group) childhood ADHD from the Multimodal Treatment of Attention-Deficit/Hyperactivity Disorder (MTA) Study were included. Participants provided self-reports on total number of MVCs they had been involved in and the time of licensure. Driving experience was estimated as the number of months since licensure. Total number of MVCs by adulthood was regressed on baseline ADHD status adjusting for sex, age at follow-up, driving experience, baseline oppositional defiant disorder/conduct disorder comorbidity, baseline household income level, adult oppositional defiant disorder/conduct disorder symptoms, adolescent and adult substance use, and adult antisocial personality disorder symptoms. We repeated the analysis using adult ADHD status (persistent versus desistant versus local normative comparison group) and symptom level as the predictor variables. Results are presented as incidence rate ratio (IRR) and CI.

Results: Childhood ADHD was associated with a higher number of MVCs (IRR = 1.45, CI = 1.15-1.82), and adult ADHD symptom persistence was associated with more MVCs than desistance (IRR = 1.46, CI = 1.14-1.86). ADHD desistance was not associated with a significantly increased risk for MVCs compared with the local normative comparison group (IRR = 1.24, CI = 0.96-1.61). Concurrent symptoms of inattention and hyperactivity/impulsivity predicted MVC risk.

Conclusion: Persistence of ADHD into adulthood is a stronger predictor of MVC risk than childhood-limited ADHD.

Short comment
Driving a vehicle is an everyday task that requires a complex integration of cognitive functions such as attention, spatial orientation, planning, perceptual-motor among other cognitive and emotional skills. Even though cars are becoming more and more “intelligent”, with many automatic functions and controls, the driver is still required to be in control in order – hopefully – to drive safely.

The MTA (Multimodal Treatment of ADHD) Study started about 20 years ago, as a cohort research to understand the impact of different treatment options for childhood ADHD. These children (initially 579 children with an age range of 7 to 10 years), were followed up periodically at several time points after the first year of treatment interventions, up to the present time.

Roy and collaborators studied 441 individuals that were included in the MTA Study since its beginning and analyzed self-reports on the total number of motor vehicle crashes (MVC), compared to a sample of healthy matched controls. Dividing the subjects according to persistence or desistance (according to criteria established by the authors) of the ADHD symptoms, they conclude that adults whose childhood ADHD persisted in adulthood had a higher risk of MVC, compared to those whose ADHD desisted, even after correction for covariables such as gender, driving experience, comorbidities and socioeconomic status.

A possible shortcoming of this study is the fact that the information about vehicle crashes was obtained from the subjects, using a self-report questionnaire. Unfortunately, the authors did not examine the possible positive influence of drug treatment of ADHD in the risk reduction of crashes. Nevertheless, the study underlines that clinicians should always investigate about driving skills of their adult ADHD patients to try to reduce all risks involved in conducting a motor vehicle.

[1] MD, PhD. Adult ADHD Research Program (PRODATH). Institute of Psychiatry, Clinics Hospital, Faculty of Medicine, University of Sao Paulo, Brazil.