Risky driving and the persistent effect of a randomized intervention focusing on impulsivity: The role of the serotonin transporter promoter polymorphism

[Display omitted] •A brief intervention in traffic schools had improved traffic behaviour for a year.•Herewith it is shown that the impact persisted for the period of four years.•Drivers’ traffic behaviour was associated with the serotonin transporter genotype.•5-HTTLPR S’ allele carriers had less violations and accidents.•Intervention reduced the high risk of 5-HTTLPR L’/L’ homozygotes. Road traffic accidents are a serious public health issue, and real-life traffic offences are an excellent indicator of the behavioural tendencies of impulsivity and risk-taking. We have previously reported on short-term efficacy of a brief intervention in driving schools to reduce traffic risks (Paaver et al., Accid. Anal. Prev., 2013; 50, 430–437), and have now addressed the question of whether does the impact of the intervention last for a few years, and whether traffic behaviour and the intervention effect are associated with the serotonin transporter polymorphism (5-HTTLPR) genotype as the central serotonin system is strongly associated with impulse control. Participants of the study were 1866 novice car-drivers (mean age 23.0, SD = 7.2 years). Data on traffic violations were obtained four years after intervention from the police database and on traffic collisions from the national traffic insurance database. DNA samples were available for 767 participants and 5-HTTLPR genotypes were classified using the triallelic model. For the observation period after the intervention, speeding, drunk driving and involvement in traffic accidents were significantly lower in the intervention group. 5-HTTLPR genotype was associated with traffic behaviour: The S’-allele carriers had significantly lower odds for speeding offences and traffic accidents. The lower prevalence of S’-allele carriers among those who had committed speeding offences was statistically significant in females, while the lower prevalence of having been involved in a traffic accident was rather observed in males. Statistically significant intervention effects were observed only in the L’/L’ homozygotes who had higher prevalence of traffic incidents. Conclusively, the brief intervention in traffic schools had a significant impact on traffic safety within subsequent four years, and traffic behaviour was associated with the serotonin transporter genotype. These findings suggest that subjects who are less likely to self-regulate their driving habits while gaining experience would benefit from training of impulsivity reco