This author interview is by Dr Thomas Brown, of McGill University. Dr Brown's full paper, Lower Cortisol Activity is Associated with First-Time Driving while Impaired, is available for download in Substance Abuse: Research and Treatment.

Please summarise for readers the content of your article.
We found that following exposure to a mildly stressful task (i.e., mental arithmetic under time pressure and a potential monetary reward), recently convicted impaired drivers showed a different hormonal response (i.e., cortisol) than observed in drivers with no conviction.

How did you come to be involved in your area of study?
The stress response is of keen interest to researchers in many areas of mental health, addiction, and risk taking. As a team committed to innovation, we have been, for almost a decade now, at the forefront of applying this process to the study of human factors in traffic safety. It seemed to us that a marker of a neurobiological process that has differentiated individuals who engage in alcohol misuse, criminal behaviour, and other forms of self-harm (e.g., suicide) would be relevant to impaired and risky driving too. More personally, as a researcher who has focussed primarily on substance use disorders, tackling a problem that can affect anyone who drinks alcohol and/or drives a car expands the potential impact my research efforts may have.

What was previously known about the topic of your article?
As far as we know, we were the first to link cortisol response to stress to driving behaviour, specifically impaired driving recidivism, in a 2005 publication. Since that time, we have replicated this study's main finding using increasingly more robust study designs in young novice drivers and now in this article, in drivers convicted for only one previous impaired driving offence.

How has your work in this area advanced understanding of the topic?
Understanding why some drivers persistently put themselves and others in harm's way remains a topic of vital interest for public health and injury prevention authorities. Some factors are consistent correlates of traffic-related risk taking, including male sex, young age, alcohol misuse, and externalizing personality traits. At the same time, discerning underlying mechanisms that explain and are capable of discerning who among, for example young males or alcohol drinkers, are at risk for persistently engaging in risky driving is still a hugely challenging undertaking. In most cases, we only reliably can flag risky drivers after they have been engaged in a serious crash or multiple risky driving situations. Without this knowledge, it is hard to deploy prevention strategies in a selective way, or to provide an intervention that targets a specific pathway to a certain risk taking behaviour. The cortisol stress response is an interesting marker in the pursuit of both these objectives.

What do you regard as being the most important aspect of the results reported in the article?
Cortisol is essential to coordinated adaptive responses to stress, as well as preparedness of the organism to cope with future challenges. This study supports the possibility that drivers with blunted baseline cortisol are more prone to repeatedly engage in risky driving because they cognitively and/or physiologically experience usually stressful events (e.g., DWI events, a crash or near-crash) in a way that fails to help and/or motivate them to avoid future events. As such, it better describes a fundamental process that may underlie their risk tasking that is otherwise hard to decipher using self-reported measures prone to bias and subjectivity.

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