Letters to the Editor
Re: Motivation and Mechanism in Motor Vehicle Collisions
Dear Editor:
We applaud Dr Dumais and others’ article on “Psychiatric Risk Factors for Motor Fatalities in Young Men” published in the November 2005 issue of the Canadian Journal of Psychiatry (1). The authors did not discuss the possible underlying mechanisms leading to fatal collisions. How might psychiatric risk factors manifest in functional driving impairments and automobile fatalities? We would like to offer some speculations of our own.
The authors make no mention of an important Axis I diagnosis strongly associated with motor vehicle collisions: attention deficit-hyperactivity disorder (ADHD). The likelihood of this association with ADHD is strengthened by demographic data on accident victims that showed significant deficits in education levels and academic achievement, which is quite commonly associated with both learning disabilities and ADHD. The literature is clear about the significantly increased risk of car accidents for adults with ADHD (2). This condition is comorbid with substance use disorder and AXIS II Cluster B personality disorder. The epidemiology of the association of ADHD with increased driving risk clearly shows strong comorbidity with antisocial personality disorder and early conduct disorder, all of which can translate into impulsive driving patterns and explosive personality structures prone to road rage (3).
Demographic details of the accidents could possibly provide information about the underlying mechanisms. It is unclear from the description of the methodology whether information regarding the nature or circumstances of these deaths was available. Particularly, single vehicle accidents at high speed with or without intoxication have commonly been described in motor vehicle accidents involving adult drivers with ADHD (1). The proposed mechanism leading to collisions in drivers with ADHD relates to deficits in executive function, specifically, a combination of response inhibition deficits and distractibility. These impairments of cognitive function translate into excessive speed, failure to disengage from high-risk manouvers, deficient defensive driving strategies, delayed response time, and slow braking because of distractibility (4).
In clinical practice it is informative to obtain a 3-generational driving history. This often reveals a strong family trend toward impulsive driving characterized by speeding, multiple car accidents, and episodes of road rage. Structured driving histories are not routinely taken in mental state examinations, but they can provide invaluable information in assessing driving risk in patients as well as providing a metric for measuring change in driving performance (5). The importance of a careful evaluation of possible comorbidities in categorical diagnoses with the potential for problem driving lies in the emerging literature about the protective value of medications for managing impulsive and aggressive behaviour patterns.
Recent literature is beginning to show that drivers with ADHD improve their driving performance, both on simulator performance and on the road, in response to stimulant challenge. These preliminary findings have significant potential for public health measures and the improvement of road safety (6).
References
1. Dumais A, Lesage A, Boyer R, Lalovic A, Chawky N, Ménard-Buteau C, and others. Psychiatric risk factors for motor vehicle fatalities in young men. Can J Psychiatry 2005;50:838–44.
2. Barkley RA. Driving impairments in teens and adults with attention-deficit/hyperactivity disorder. Psychiatr Clin North Am 2004;27:233–60.
3. Jerome L. Road rage: old wine in a new bottle. Can J Psychiatry 2004;49:709–10.
4. Barkley RA. The executive functions and self-regulation: an evolutionary neuropsychological perspective. Neuropsychol Rev 2001;11:1–29.
5. Jerome L. Forensic risk assessment and dangerous driving. Can J Psychiatry2005;50:739–40.
6. Barkley RA, Murphy KR, O’Connell T, Connor DF. Effects of two doses of methylphenidate on simulator driving performance in adults with attention deficit hyperactivity disorder. J Safety Res 2005;36:121–31.
Laurence Jerome, MD, Al Segal, PhD
London, Ontario
Declan Quinn, MD
Saskatoon, Saskatchewan
|
