Driving risks of young drivers with symptoms of attention deficit hyperactivity disorder: association with the dopamine transporter gene VNTR polymorphism

Road traffic injuries are a leading cause of death for young adults, and young drivers with higher expression of symptoms of attention deficit-hyperactivity disorder (ADHD) could pose an even greater risk in traffic. Dopaminergic dysfunction has been found to occur in ADHD, with the dopamine transporter (DAT) gene VNTR polymorphism (<i>DAT1</i> VNTR; rs28363170) being one of the most consistent genetic markers. Thus, we aimed at clarifying how the ADHD symptoms and the <i>DAT1</i> VNTR relate to risk-taking behaviour in traffic, impulsivity and driving anger in young drivers. We used data of two traffic behaviour study samples (<i>n</i> = 741, mean age = 23.3 ± 7.2 years; <i>n</i> = 995, mean age = 22.9 ± 8.1 years) and the Estonian Children Personality Behaviour and Health Study (ECPBHS; traffic behaviour data <i>n</i> = 1,016, mean age = 25.2 ± 2.1 years). ADHD symptoms were assessed by self-report with the Adult ADHD Self-Report Scale (ASRS v1.1) and impulsivity with the Adaptive and Maladaptive Impulsivity Scale. Traffic behavioural measures were either self-reported (Driver Behaviour Questionnaire, Driving Anger Scale) or obtained from databases (registered accidents and violations). Drivers with more self-reported ADHD symptoms also reported more risk-taking in traffic and had more of recorded traffic accidents and violations. <i>DAT1</i> 9 R carriers had a higher probability of high traffic risk behaviour only if they also had ADHD symptoms. Higher level of ADHD symptoms is a significant risk factor in traffic, and carrying of the <i>DAT1</i> 9 R allele appears to aggravate these risks.