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Psychological distress and crash risk

Does psychological distress increase crash risk for young drivers?

‘Psychological distress’ is a mental health state that includes symptoms of both depression and anxiety. There are several reasons why a link between psychological distress and motor vehicle crash might exist.  People who are experiencing psychological distress  may have physical and cognitive impairments related to slower reaction times, which could increase the risk of a crash when driving. Symptoms such as disturbed sleep and poor concentration, which often go hand-in-hand with psychological distress, can also affect driving.  Some  medications taken for psychological distress may also impair alertness and driving ability. It has also been shown that people experiencing psychological distress are more likely to misuse alcohol or drugs and potentially engage in physical self-harm. As self-harm has recently been shown to significantly increase young drivers’ crash risk, this also led to the question as to  whether psychological distress is also related to higher crash risk.

Previous research on this issue has shown both increased and decreased risk of crash related to psychological distress.  The quality of these past studies has, however, been limited, with nearly all studies measuring both psychological distress and crash risk at the same point in time so that it is not possible to know which one may have come first – particularly difficult since we know that having a crash is linked to subsequent psychological distress in some individuals.  Also these past studies were not able to control for important potential confounders such as exposure to driving, alcohol and drug use or having had a previous crash.

A new Australian study has examined psychological distress among young drivers before they crash, and looked at associations between this and their risk of crash up to two years later – also controlling for  important confounders such as time spent driving each week and alcohol/other drug use. In this study of 20,822 newly licensed NSW drivers aged 17-24 years, no increased risk of any crash type (including a single vehicle crash) was observed for youth experiencing psychological distress compared to those not experiencing psychological distress. In fact, there was a protective effect for those experiencing a moderate level of psychological distress – that is they were less likely to have a crash.  Given this finding and the lack of strong research indicating otherwise, this suggests initiatives to address psychological distress generally are not a priority to reduce crash risk among young drivers.  However, as research has demonstrated increased risk of crashing for young drivers who engage in self-harm , interventions for that group are more likely to have an effect on crash risk.

What are the potential issues?

While this latest finding of no relationship between psychological distress and increased crash risk is drawn from only one study, it is a high quality study. Nonetheless, as psychological distress was only measured in one point in time and can vary over time, future studies would benefit from measuring  psychological distress at several points in time and the impact on risk of crashes.

Factbase Recommendation

No protective initiatives are needed to address psychological distress and crash risk, however action should be taken for those who report self-harm.

References

Blows S, Ivers RQ, Connor J, Ameratunga S, Woodward M, Norton R. Marijuana use and car crash injury. Addiction, 2005;100:605–11.

Brunnauer A, Laux G, Geiger E, Soyka M, Möller HJ. Antidepressants and driving ability: Results from a clinical study. Journal of Clinical Psychiatry, 2006;67:1776–81.

Bulmash EL, Moller HJ, Kavumov L, Shen J, Wang X, Shapiro CM. Psychomotor disturbance in depression: Assessment using a driving simulator paradigm. Journal of Affective Disorders, 2006;93:213–8.

Connor J, Norton R, Ameratunga S, Robinson E, Civil I, Dunn R, Bailey J, Jackson R. Driver sleepiness and risk of serious injury to car occupants: Population based case control study. British Medical Journal, 2002;324:1125.

Herman H, Saxena S, Moodie R (Eds). Promoting mental health: concepts, emerging evidence, practice. Report of the World Health Organization Department of Mental Health and Substance Abuse in collaboration with the Victorian Health Promotion Foundation and the University of Melbourne 2005 [Online]. Available at: http://www.who.int/mental_health/evidence/en/. Accessed March 26, 2009.

Martiniuk ALC, Glozier N, Senserrick T, Ivers RQ, Patton GC, Lam LT, Williamson A, Stevenson M, Norton R, Woodward M.  Psychological distress: Does it increase risk of motor vehicle crash in young drivers?  Journal of Adolescent Health. Epub May 18, 2010.


Psychological distress and crash risk