Pubdate: Tue, 16 Jun 2015
Source: New York Times (NY)
Copyright: 2015 The New York Times Company
Author: Benedict Carey


Marijuana use did not increase among teenagers in the states in which 
medical marijuana has become legal, researchers reported Monday.

The new analysis is the most comprehensive effort to date to answer a 
much-debated question: Does decriminalization of marijuana lead more 
adolescents to begin using it?

The study found that states that had legalized medical use had higher 
prevailing rates of teenage marijuana use before enacting the laws, 
compared with states where the drug remains illegal. Those higher 
levels were unaffected by the changes in the law, the study found.

The report, published in The Lancet Psychiatry, covered a 24-year 
period and was based on surveys of more than one million adolescents 
in 48 states. The research says nothing about the effect of 
legalizing recreational use, however.

A primary concern on both sides of the debate over medical marijuana 
has been that loosening marijuana restrictions might send the wrong 
message to young people, and make the drug both more available and 
more appealing. Teenagers who develop and sustain a heavy, daily 
habit increase their risk of having cognitive difficulties later on, 
several studies now suggest.

Previous research on usage trends in the wake of the laws has been 
mixed, some reporting evidence of an increase among adolescents and 
others - including two recent, multistate studies - finding no 
difference. The new analysis should carry far more weight, experts 
said, not only because of its size and scope but also because the 
funders included the National Institute of Drug Abuse, whose director 
has been outspoken about the risks of increased use.

"We have a war going on over marijuana, and I think both sides have 
been guilty at times of spinning the data," said Dr. Kevin Hill, an 
assistant professor of psychiatry at Harvard and director of the 
substance abuse consultation service at McLean Hospital. "It's nice 
to have a scientifically rigorous study to guide policy."

Dr. Hill, author of the book "Marijuana: The Unbiased Truth About the 
World's Most Popular Weed," said this study was about as definitive 
as could be expected.

Researchers opposed to legalizing marijuana, for medical or other 
purposes, disagreed, saying the study would have to go further to be 

"Medical marijuana laws vary drastically across the U.S. and often 
take years to be implemented, so what we need to see is the 
longer-term effects of these laws and the accompanying 
commercialization efforts, which this study does not do," said Kevin 
Sabet, a former Obama administration adviser and president of the 
group Smart Approaches to Marijuana, or SAM, which opposes legalization.

In the study, a research team led by Deborah Hasin of Columbia 
University analyzed data from a large, continuing University of 
Michigan survey of 8th, 10th and 12th graders, asking about their use 
of a variety of drugs, including alcohol, tobacco and marijuana.

The team focused on responses to several questions in particular, 
including those asking about use within the last 30 days and 
frequency of use. The researchers adjusted the data for factors known 
to correlate with marijuana use, like gender, education level of 
parents, and whether a school was urban or rural.

The overall rate of use among teenagers in states that passed laws 
was 16 percent, compared with 13 percent in those that had not, the 
analysis found. The researchers then compared samples of teenagers 
before and after laws passed in specific states: for example, before 
and after August 2013 in Illinois, and before and after April 2007 in 
New Mexico.

"We showed no hint of an increase at all after the laws were passed," 
Dr. Hasin said.

The University of Michigan surveys have found that marijuana use 
among teenagers has been generally on the rise, in contrast to trends 
in alcohol, opioid and nicotine use - and perceptions of marijuana's 
health risks are steadily shrinking.

Those risks are probabaly small for occasional users who are 
adolescents, most experts say. But heavy, daily users who start young 
are at risk of blunting their mental acuity over time, several 
studies have found, because of biological and social factors that are 
not yet understood.

The research group is planning to study the effect on usage trends 
when recreational marijuana is legalized, as in Colorado.
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MAP posted-by: Jay Bergstrom