Book Description

"Background: According to the World Health Organization, road traffic crashes represent the single leading cause of death for young people. Road traffic crashes are largely preventable, yet the precise mechanisms underlying individual driving risk remain relatively unidentified. Some risky drivers are over-represented among those involved in serious and fatal road traffic crashes, including those who misuse alcohol. Understanding what drives their risk taking is a key to developing evidence-based and effective prevention programs. Research focusing on the causes of risky driving has examined neurobiological markers of risk taking, such as cortisol, serotonin, and adrenaline. The steroid hormone testosterone has received substantial attention in relation to risk taking, but not specifically related to driving behaviour. Testosterone has been associated with sensation seeking and impulsivity, two consistent correlates of risky driving. Furthermore, interactions between testosterone and alcohol in relation to sensation seeking and impulsivity have been observed, potentially making testosterone a specific factor in driving while impaired with alcohol. In this experiment, four hypotheses were tested: H1) Young drivers with higher testosterone level show higher mean speed in simulation than young drivers with lower testosterone level; H2) Alcohol moderates the relationship between testosterone level and mean speed; H3) Sex moderates the relationship between testosterone level and mean speed; H4) Sensation seeking and impulsivity mediate the relationship between testosterone level and mean speed under alcohol. Methods: This study is part of a larger between-subject, randomized, placebo-controlled experiment. Eleven male and eleven female drivers aged 18-34 years were recruited and their saliva assayed for endogenous testosterone level using radioimmunoassay. Participants also responded to questionnaires assessing sensation seeking and impulsive personality characteristics, and performed two driving simulation tasks, one at BAC (blood alcohol content) of 0% (no-alcohol condition) and another at a positive BAC of 0.02% - 0.05% (i.e., alcohol condition). Results: H1 was not supported by the findings; young drivers with higher testosterone level did not report higher simulated speed than young drivers with lower testosterone level, p > .05. H2 was supported. A significant alcohol X testosterone interaction was detected (p = .04; partial Eta-squared = .20). Specifically, young drivers with higher testosterone level reported higher mean speed than drivers with lower testosterone level, but only after alcohol consumption. Sex was not a significant moderator of the relationship between testosterone level and simulated speed (p > .05). Neither sensation seeking nor impulsivity mediated the relationship between testosterone level and simulated speed under alcohol (p > .05).Conclusion: Interaction between testosterone hormone and alcohol may be one mechanism contributing to risky driving under legal BAC (in Canada