Pubdate: Sun, 25 Jan 2015
Source: Philadelphia Inquirer, The (PA)
Copyright: 2015 Philadelphia Newspapers Inc
Contact:  http://www.philly.com/inquirer/
Details: http://www.mapinc.org/media/340
Author: Don Sapatkin

WOULD LEGALIZED POT REDUCE FATAL TRAFFIC ACCIDENTS?

With medical marijuana legal in nearly half the states and a narrow 
majority of Americans saying they favor recreational availability as 
well, worried medical researchers are scrambling to project the 
potential impact on public health issues ranging from addiction to 
cognition to traffic deaths.

But here's a counterintuitive question: Could easier access to 
marijuana reduce fatal car crashes?

The answer, according to a new study of traffic fatalities in nine 
states - including New Jersey - with high rates of toxicology 
testing, is admittedly hazy.

"Increased availability of marijuana to young adults in U.S. states 
that have passed medical and recreational use allowance may have 
positive spillover effects on alcohol, reducing use to some degree 
among young adults," the authors write in the journal Injury 
Epidemiology. But, they hasten to add, that may not reduce traffic deaths.

Still, the paper is intriguing not so much for its conclusions as for 
how it asks the questions. They are suggested by a combination of 
traffic fact and economic theory.

Alcohol kills far more drivers than any other drug. The theory has to 
do with how two goods interact: "When one substance becomes more 
legally accessible, what happens to the prevalence of other 
substances?" the authors ask.

In economic terms, if two goods are complements, then demand for one 
increases with availability of the other. If they are substitutes, 
the opposite happens. Past research findings on the relationship 
between alcohol and marijuana have been mixed.

For their new study, the Columbia University scientists examined 
toxicology data for 7,191 drivers ages 16 to 25 who died within one 
hour of a crash between 1999 and 2011. Nearly 37 percent tested 
positive for alcohol alone, 6 percent for marijuana alone, and 8 
percent for both.

The analysis looks at how those proportions changed according to age, 
and particularly the one variable that consistently affects 
availability of alcohol: turning 21.

Alcohol use increased 14 percent after age 21 compared with before, 
and marijuana use decreased 24 percent, suggesting the substances are 
substitutes.

But the trend was up (22 percent) among drivers who tested positive 
for both drugs, pointing to a complementary relationship there.

Teasing a meaningful conclusion from the varying percentages is 
difficult, especially as they represent different starting points. 
Many more drivers tested positive for alcohol alone than for either 
other scenario.

Another issue in this study is that the independent variable was the 
legal drinking age.

"This shows the impact of alcohol on marijuana, not necessarily 
marijuana on alcohol," said lead author Katherine Keyes, an assistant 
professor at Columbia's Mailman School of Public Health who studies 
substance-abuse epidemiology. "It is suggestive."

Although Washington was one of the states studied, all the data were 
collected long before the first recreational pot went on sale there 
last summer. Colorado, where business has been booming for a year, 
was not part of the study. Researchers are looking at it now, however.

Public opinion on marijuana has been shifting rapidly, with 51 
percent of Americans favoring legalization, Gallup reported in 
October. Although recreational use has been legalized in just the two 
states, medical use is allowed in 23, including New Jersey.

In Pennsylvania, a medical marijuana bill overwhelmingly passed the 
Senate before failing in the House last year. The new House Majority 
Leader, David Reed (R., Indiana), was co-sponsor of a version of the 
bill in the House. Gov. Wolf supports legalization for medical use.

The new research paper, while suggesting an increase in marijuana use 
could lead to a slight decrease in alcohol-related deaths, notes many 
other factors must be considered and the net result "may be null or 
even detrimental for fatality rates overall."

Highly potent marijuana can be just as lethal on the highway, for 
example, and strong demand would likely mean more people driving 
high. Once the drug is legalized, state regulators have some control over both.

"The way the laws are implemented are going to matter a lot," Keyes said.
- ---
MAP posted-by: Jay Bergstrom