Pubdate: Tue, 18 Feb 2014
Source: Times-Tribune, The (Scranton PA)
Copyright: 2014 Townnews.com
Contact:  http://www.thetimes-tribune.com
Details: http://www.mapinc.org/media/4440
Author: Maggie Koerth-Baker, the New York Times
Page: C6

POT-USING DRIVERS ELUSIVE

Detection a Big Issue As Marijuana Use Grows

If you are pulled over on suspicion of drunken driving, the police
officer is likely to ask you to complete three tasks: Follow a pen
with your eyes while the officer moves it back and forth; get out of
the car and walk nine steps, heel to toe, turn on one foot and go
back; and stand on one leg for 30 seconds.

Score well on all three of these Olympic events, and there's a very
good chance that you are not drunk. This socalled standard field
sobriety test has been shown to catch 88 percent of drivers under the
influence of alcohol.

But it is nowhere near as good at spotting a stoned driver. In a 2012
study published in the journal Psychopharmacology, only 30 percent of
people under the influence of THC, the active ingredient in marijuana,
failed the field test. And its ability to identify a stoned driver
seems to depend heavily on whether the driver is accustomed to being
stoned.

A 21-year-old on his first bender and a hardened alcoholic will both
wobble on one foot. But the same is not necessarily true of a driver
who just smoked his first joint and the stoner who is high five days a
week. In another study, 50 percent of the less frequent smokers failed
the field test.

As more states legalize medical and recreational marijuana,
distinctions like these will grow more and more important. But
science's answers to crucial questions about driving while stoned -
how dangerous it is, how to test for impairment and how the risks
compare to driving drunk - have been slow to reach the general public.

"Our goal is to put out the science and have it used for
evidence-based drug policy," said Marilyn A. Huestis, a senior
investigator at the National Institute on Drug Abuse. "But I think
it's a mishmash."

A 2007 study found that 12 percent of the drivers randomly stopped on
U.S. highways on Friday and Saturday nights had been drinking.

Six percent of the drivers tested positive for marijuana - a number
that is likely to go up with increased availability. Some experts and
officials are concerned that the campaign against drunken driving has
not gotten through to marijuana smokers.

[sidebar]

Pot Versus Alcohol: The Numbers

Some scientists say it's clear that marijuana use causes deficits that
affect driving ability. Several researchers, working independently of
one another, have come up with the same estimate: a twofold increase
in the risk of an accident if there is any measurable amount of THC in
the bloodstream.

That estimate is low, however, compared with the dangers of drunken
driving. A recent study found that 20year-old drivers with a
blood-alcohol content of 0.08 percent - the legal limit for driving -
had an almost twentyfold increase in the risk of a fatal accident. For
older adults, up to age 34, the increase was ninefold.
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