Pubdate: Thu, 21 Jul 2011 Source: Victoria Times-Colonist (CN BC) Copyright: 2011 Times Colonist Contact: http://www2.canada.com/victoriatimescolonist/letters.html Website: http://www.timescolonist.com/ Details: http://www.mapinc.org/media/481 Author: Pamela Fayerman IS THERE A CORRELATION BETWEEN MARIJUANA USE, VEHICLE CRASHES? Blood to Be Taken From Injured Drivers in Bid to Answer This Injured drivers taken to B.C. hospitals over the next five years will help answer the question: Do those who are high on marijuana cause more crashes than sober drivers? In the marijuana-impairment study -- the first of its kind in Canada -- injured drivers will not be asked permission before their blood is collected. Since the data is collected anonymously and not used to pursue legal charges, researchers don't have to seek approval from drivers to analyze their blood under the ethics-approved terms of the study. Blood is drawn for treatment of any injuries and the excess amount is then analyzed. The sample is assigned a code that is not shared with police, and the resulting data is then linked to police accident reports to eventually show researchers if cannabis contributed to the accident. A recent random sampling of B.C. drivers showed that 10 per cent were impaired by alcohol and 7.2 per cent by drugs, usually marijuana or cocaine. Concentrations of THC, the active ingredient in cannabis, are what will be measured in the study, which is led by Dr. Jeffrey Brubacher, an emergency doctor at Vancouver General Hospital. After alcohol, cannabis is the most widely used intoxicating substance in the world; in the aforementioned B.C. survey it accounted for about two-thirds of the drugs detected after police roadside stops (followed by cocaine). Many marijuana users think it's less hazardous because cannabis tends to make people drive more slowly and less aggressively than, say, drivers who are drunk on alcohol, according to studies. But, at the same time, drivers high on marijuana have a harder time staying within lanes and their reflexes are slower, which means they are more likely to crash into obstacles that suddenly appear. On the other hand, "cannabis users tend to overestimate their impairment whereas people who used alcohol underestimate theirs," Brubacher stated in an explanation of his study in the B.C. Medical Journal. Brubacher said data on the first 100 injured drivers have already been collected for the study, which aims to include information on 3,000 crashinvolved drivers at five B.C. hospitals. THC levels in blood -- which are measurable no matter how the cannabis is consumed (smoked, sprayed, drunk, or eaten) -- yield a blood THC concentration considered more accurate than THC metabolites in urine. Brubacher said urine metabolites remain active for days after cannabis exposure. "Our primary objective is to determine whether injured drivers who used cannabis before a motor vehicle accident are more likely to have caused the crash than those who did not," said Brubacher, adding that the number of crashes caused by impaired drivers will be compared to a control group of drivers who were found to be not culpable. The ultimate goal of the $1-million study, funded by the federal Canadian Institutes of Health Research, is to help traffic-safety experts develop safer driving policies. It is possible, for example, that the study might show whether there should be a legal cutoff level for THC blood concentration, just as there is for alcohol. - --- MAP posted-by: Richard R Smith Jr.