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.
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MAP posted-by: Jay Bergstrom