Angry drivers have a higher risk of collision

"Even minor aggression, such as swearing, yelling or making rude gestures, can increase the risk of a collision," says lead author Dr. Christine Wickens, scientist in CAMH's Institute for Mental Health Policy Research. The study was published in Transportation Research Part F: Traffic Psychology and Behaviour.

Nearly one-third of Ontario drivers reported acts of minor aggression. Drivers who said they had also made threats, attempted or succeeded in damaging another car or hurting someone, had the highest odds of collision -- 78 per cent higher than those whose aggression was considered minor. This risk is comparable to those who use cannabis and drive, Dr. Wickens notes, and represents two per cent of Ontarians.

Study findings were drawn from the CAMH Monitor, an ongoing survey of Ontario adults' mental health and risk behaviours, using responses from 12,830 people between 2002 and 2009. While past research has explored the relationship between aggression and collisions, this is the largest population-level study to analyze this association.

Just under eight per cent of Ontarians reported having a car collision in the previous year. This group was analyzed in relation to their reported aggressive behaviour, while controlling for other factors that could increase the risk of collision such as age, sex, cannabis or alcohol use and other factors.

It was striking how the risk of collision rose as the levels of aggression increased, says Dr. Wickens. People who reported no driving-related aggression had the lowest odds of collision, with increasing risk among those who had minor aggression, and the highest risk of all among those who reported both minor and more serious aggression.

"The results clearly show that aggression is related to the risk of collision," says Dr. Wickens. While the study doesn't show that specific cases of anger directly caused a collision, the strong association suggests these drivers may have a greater chance of a collision because they either drive more aggressively or are distracted by their anger from other hazards on the road.

"Reducing driver anger and aggression would potentially reduce the risk of collisions," says Dr. Wickens. There are well established approaches to manage stress and anger, ranging from deep breathing techniques and listening to music to cognitive anger management programs. Leaving enough time on a car trip to reach your destination could also reduce stress, the researchers write.