Pubdate: Tue, 10 Feb 2015 Source: Minneapolis Star-Tribune (MN) Copyright: 2015 Star Tribune Contact: http://www.startribunecompany.com/143 Website: http://www.startribune.com Details: http://www.mapinc.org/media/266 Author: Christopher Ingraham, Washington Post STUDY: STONED DRIVERS SAFER THAN DRUNK ONES Study Underscored That THC Levels Don't Correlate With Driver Impairment. WASHINGTON - A new study from the National Highway Traffic Safety Administration found that drivers who use marijuana are at a significantly lower risk for a crash than drivers who use alcohol. And after adjusting for age, gender, race and alcohol use, drivers who tested positive for marijuana were no more likely to crash than who had not used drugs or alcohol before driving. For marijuana, and for a number of other legal and illegal drugs including antidepressants, painkillers, stimulants and the like, there is no statistically significant change in the risk of a crash associated with using that drug before driving. But overall alcohol use, measured at a blood alcohol concentration (BAC) threshold of 0.05 or above, increases the odds of a wreck nearly sevenfold. The study's findings underscore an important point: that the measurable presence of THC (marijuana's primary active ingredient) in a person's system doesn't correlate with impairment in the same way that blood alcohol concentration does. The NHTSA doesn't mince words: "At the current time, specific drug concentration levels cannot be reliably equated with a specific degree of driver impairment." There are a whole host of factors why detectable drug presence doesn't indicate impairment the way it does with alcohol. "Most psychoactive drugs are chemically complex molecules, whose absorption, action and elimination from the body are difficult to predict," the report authors wrote, "and considerable differences exist between individuals with regard to the rates with which these processes occur. Alcohol, in comparison, is more predictable." In heavy marijuana users, THC can be detectable in the body days or even weeks after the last use . Several states have passed laws attempting to define "marijuana-impaired driving." Colorado, for instance, sets a blood THC threshold of 0.5 nanograms per milliliter. But that number says next to nothing about whether a person is impaired or fit to drive. Better roadside mechanisms are needed for detecting marijuana-related impairment. Several companies are developing pot breathalyzers for this purpose. There's a lot more research to be done into the effects of marijuana use on driving ability, particularly to get a better sense of how pot's effect on driving diminishes in the hours after using. - --- MAP posted-by: Jay Bergstrom