Pot smokers are risky drivers

Young men who are impulsive thrill-seekers are more likely to admit to driving while high on marijuana, Canadian researchers report.

Men who drove under the influence of cannabis were also more likely to report certain risky driving behaviours, and tend to get in more accidents, Drs Isabelle Richer and Jacques Bergeron of the University of Montreal say.

Based on the findings, according to Richer and Bergeron, any public health messages intended to discourage people from driving while high "should include an arousing and unconventional format" so they won't be "redundant and boring" for their intended audience.

After alcohol, cannabis is the mind-altering substance most often found in the urine or blood of drivers after a crash, the researchers note in the journal Accident Analysis and Prevention.

How the study was done
Studies have shown that people's driving skills are impaired within the first hour after smoking pot, they add. And it's also possible, according to Richer and Bergeron, that people who get behind the wheel after smoking marijuana are also by nature more likely to be dangerous drivers.

To investigate, Richer and Bergeron looked at 83 men ranging in age from 17 to 49, of whom 30 admitted to being pot smokers.

Among these individuals, 80% said they had driven under the influence of marijuana in the past 12 months. Of all the study participants, 35% had been involved in at least one car crash in the past three years.

The researchers had the men complete personality tests, and then examined their driving behaviour by having them use a driving simulator.

What the study revealed
During the driving test, a car was positioned in front of the driver that would slow down when the driver was behind it, but speed up when the driver tried to pass. The study participants were also required to complete the driving test under time pressure.

Study participants with high scores on personality tests measuring sensation-seeking and impulsivity were more likely to say they had driven under the influence of cannabis in the past year. The pot-smoking drivers were also more likely to report having engaged in risky driving, meaning driving in a careless way that could hurt others but isn't intended to do so; and negative emotional driving, for example, getting angry with other motorists.

These men were also more likely to exhibit these behaviours in the simulation tests. There was a slight increased likelihood that the pot smokers would get in crashes, and they were also more likely to admit to drinking and driving.

"Media campaigns promoting traffic safety tend to emphasise rational decision-making approaches involved in driving," the researchers say. But such strategies might not work for young men who drive after smoking marijuana, they add. "It is therefore important to strike a balance between arousing and educational messages."

They conclude: "On-road risky behaviours tend to be inter-correlated, so interventions should focus on a broad range of dangerous behaviours." – (Reuters Health, March 2009)

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