New research demonstrates high marijuana risk

We’ve long known the affect of alcohol on our behaviour and activities, but more and more research is being undertaken on the effect of marijuana. The purpose of the study was not to stop people using marijuana, but to increase the level of public knowledge of its effect on driving safety.

A new study by the USA National Institute on Drug Abuse has published the results of recent study, conducted using a driving simulator. The study group was composed of 18 occasional cannabis smokers, 13 men and 5 women, all between the ages of 21 and 37. Each took 6 x 45-minute sessions in the simulator, and were given either a low or high dose of marijuana, alcohol, or a placebo.

More than 250 performance indicators were recorded, but with a concentration on three:

  • weaving within the lane
  • the number of times the car left the lane
  • the speed of the weaving

The participants given alcohol showed a tendency to weave, and to weave more quickly. Those given marijuana did not. They did, however, weave more often, similar to that of a driver at the 0.08 level alcohol, a higher level of course than is the Australian alcohol limit.

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Importantly the study shows that alcohol and marijuana when used together increase the ‘high’, and delay any impairment.

Dr. Marilyn Huestis, the lead investigator on the study, said, “I think this has added really good knowledge from a well-designed study to add to the current debate on marijuana’s effects on road safety”.

In Australia, police have been conducting roadside saliva testing for marijuana and other drugs since 2004 in Victoria, and in other states a couple of years later. Those running the risk of driving while under the influence do so without full knowledge of how much they have ingested, as the effect can be delayed, and the level varying, due to gender, age, individual metabolism, and the strength of the marijuana.

For more information an driving and drugs, read the fact sheet The facts about roadside drug testing, from the Australian Drug Foundation.

Does it concern you might be sharing the road with drivers under the influence of marijuana?