Self-harm in adolescence and risk of crash: a 13-year cohort study of novice drivers in New South Wales, Australia

INTRODUCTION

Self-harm and suicide are leading causes of morbidity and death for young people, worldwide. Previous research has identified self-harm is a risk factor for vehicle crashes, however, there is a lack of long-term crash data post licensing that investigates this relationship. We aimed to determine whether adolescent self-harm persists as crash risk factor in adulthood.

METHODS

We followed 20 806 newly licensed adolescent and young adult drivers in the DRIVE prospective cohort for 13 years to examine whether self-harm was a risk factor for vehicle crashes. The association between self-harm and crash was analysed using cumulative incidence curves investigating time to first crash and quantified using negative binominal regression models adjusted for driver demographics and conventional crash risk factors.

RESULTS

Adolescents who reported self-harm at baseline were at increased risk of crashes 13 years later than those reporting no self-harm (relative risk (RR) 1.29: 95% CI 1.14 to 1.47). This risk remained after controlling for driver experience, demographic characteristics and known risk factors for crashes, including alcohol use and risk taking behaviour (RR 1.23: 95% CI 1.08 to 1.39). Sensation seeking had an additive effect on the association between self-harm and single-vehicle crashes (relative excess risk due to interaction 0.87: 95% CI 0.07 to 1.67), but not for other types of crashes.

DISCUSSION

Our findings add to the growing body of evidence that self-harm during adolescence predicts a range of poorer health outcomes, including motor vehicle crash risks that warrant further investigation and consideration in road safety interventions. Complex interventions addressing self-harm in adolescence, as well as road safety and substance use, are critical for preventing health harming behaviours across the life course.

Socioeconomic status during youth and risk of car crash during adulthood. Findings from the DRIVE cohort study

BACKGROUND

Young drivers of low socioeconomic status (SES) have a disproportionally high risk of crashing compared with their more affluent counterparts. Little is known if this risk persists into adulthood and if it differs between men and women.

METHODS

We used data from a 2003/2004 Australian survey of young drivers (n=20 806), which included measures of drivers' demographics and established crash risk factors. These data were linked to police-reported crash, hospital and death data up to 2016. We used negative binomial regression models to estimate the association between participants' SES, with car crash.

RESULTS

After adjusting for confounding, drivers of lowest SES had 1.30 (95% CI 1.20 to 1.42), 1.90 (95% CI 1.25 to 2.88), 3.09 (95% CI 2.41 to 3.95) and 2.28 (95% CI 1.85 to 2.82) times higher rate of crash, crash-related hospitalisation, crash in country areas and crash on streets with a speed limit of 80 km/hour or above compared with drivers of highest SES, respectively. For single-vehicle crashes, women in the lowest SES groups had 2.88 (95% CI 1.83 to 4.54) times higher rate of crash compared with those in the highest SES group, but no differences were observed for men from different SES groups.

CONCLUSION

Young drivers who lived in areas of low SES at the time of the survey had a sustained increased risk of crash over the following 13 years compared with drivers from the most affluent areas. Our findings suggest that in addition to traditional measures, road transport injury prevention needs to consider the wider social determinants of health.