There are beliefs about how cannabis affects a person’s driving abilities, but there isn’t a lot of evidence to offer as proof.  A scientist in Ontario is trying to change that.

Dr. Robert Mann with the Centre for Addiction and Mental Health (CAMH) has been testing volunteers since 2013, using a simulated road test.

“There’s a fair amount of uncertainty on the impact of cannabis on driving skills,” Mann said. “There’s still a discussion, still an argument, about what the effects are.”

So Mann and his colleagues at CAMH have been collecting data for a clinical study to examine the relationship, and are hoping to publish the results next year.

“The (existing) evidence has pretty much convinced me that if you are driving under the influence of cannabis, you are at an increased risk of getting in a collision … We don’t know what dose relates to that yet.” he said

The CAMH study chose to focus on volunteers in the 19-to-25 year old range because that age group is more likely to drive high than drunk, according to Mann.

All subjects taking part are screened, and those who are chosen are given a joint to smoke that is either regular cannabis or a placebo.  They are then put through a test on a driving simulator that looks much like a video game.

Mann says the volunteers repeat the test 24 and 48 hours later so researchers can measure any lingering effects.

As of now 75 people have participated, with the goal of having 114 volunteers take the test before the study is complete next spring.