Pubdate: Sun, 13 Jan 2013
Source: Honolulu Star-Advertiser (HI)
Copyright: 2013 Star Advertiser
Author: Roni Caryn Rabin, New York Times


In the '60s, marijuana was a hallmark of the counterculture, along
with free love, bell bottoms, long hair and bandannas. But marijuana
has had the most staying power.

This month, in a remarkable first, the recreational use of marijuana
became legal (depending on your definition) in Colorado and Washington
state. More than a dozen other states have decriminalized possession
of small amounts, and Massachusetts recently became the 18th state to
allow its use for medicinal purposes.

Although federal law still bans both the sale and possession of
marijuana, President Barack Obama has said the federal government has
"bigger fish to fry" and will not aggressively prosecute tokers in
states where its use is legal.

The rise of marijuana as an adult pastime is a victory for those who
have always contended that its hazards were overblown. Proponents of
legalization argue that marijuana is much safer to use than alcohol,
saying that it is virtually impossible to overdose on marijuana.

While marijuana can be addictive, scientists generally agree that
fewer than 10 percent of marijuana smokers become dependent on the
drug, compared with 15 percent for alcohol, 23 percent for heroin and
32 percent for tobacco. Marijuana contains carcinogens, including tar
and other toxins similar to those found in tobacco, but people
generally do not smoke marijuana in the same amounts as cigarettes.

Still, legalization takes users into murky territory. Even though
marijuana is the most commonly used illegal drug in the United States,
questions about its health effects remain.

For starters, this is not your parents' pot. Today's marijuana is much
more potent: The mean concentration of THC, the psychoactive
ingredient, in confiscated cannabis more than doubled between 1993 and

Increased potency might be having unforeseen consequences. The human
brain's cannabinoid receptors are typically activated by naturally
occurring chemicals in the body called endocannabinoids, which are
similar to THC. There is a high density of cannabinoid receptors in
parts of the brain that affect pleasure, memory and concentration.
Some research suggests that these areas continue to be affected by
marijuana use even after the "high" dissipates.

"It's much more potent marijuana, which may explain why we've seen a
pretty dramatic increase in admission to emergency rooms and treatment
programs for marijuana," said Dr. Nora D. Volkow, director of the
National Institute on Drug Abuse.

Those in favor of legalizing marijuana say that the increase in
potency has been exaggerated and that when users have more powerful
pot, they smoke less.

Teenagers might be more vulnerable to addiction, however, and those
who start smoking pot at a younger age are at higher risk. About 1 in
6 will become addicted, Volkow said. Young adults who start smoking
marijuana at earlier ages also tend to smoke much more, and more
often, than those who start in their later teens, researchers say.

In users who develop a dependence or addiction, quitting can cause
intense withdrawal symptoms, such as anxiety, trouble sleeping, lack
of appetite, mood swings, irritability and depression, experts say.

Both Colorado and Washington restricted marijuana use to adults age 21
and older when they legalized recreational use in November. But
experts worry that the perception of marijuana is changing because its
stigma as an outlawed drug has eroded.

"When people can go to a 'clinic' or 'cafe' and buy pot, that creates
the perception that it's safe," said Dr. A. Eden Evins, director of
the Center for Addiction Medicine at Massachusetts General Hospital in
Boston. "Before we unleash the powers of the marketplace to woo people
to use this addictive substance, we need to better understand who is
at risk."

"Once moneyed interests are involved, this trend will be difficult to
reverse," she added.

The most disturbing new studies about early teenage use of marijuana
show that young adults who started smoking pot regularly before they
were 16 performed significantly worse on cognitive tests of brain
function than those who had started smoking later in adolescence. They
performed particularly poorly on tests assessing executive function,
which is responsible for planning and abstract thinking, as well as
understanding rules and inhibiting inappropriate responses.

In addition, imaging scans found detectable differences in how their
brains worked, said Staci Gruber, the lead author of these studies and
director of the cognitive and clinical neuroimaging core at the
imaging center at McLean Hospital in Boston. Imaging scans found
alterations in the frontal cortex white matter tracts of the brain in
the early-starters, she said, that are associated with

"The frontal cortex is the last part of the brain to come online and
the most important," Gruber said. "Early exposure perhaps changes the
trajectory of brain development, such that ability to perform complex
executive function tasks is compromised."

A recent study showing a drop in IQ scores among teenagers who are
regular pot smokers is especially troubling, Evins said. The study
found that people who started smoking marijuana as teenagers and used
it heavily for decades lost IQ points over time, while those who
started smoking as adults did not.

"If parents who are spending thousands of dollars on SAT prep courses
knew about the cognitive effects marijuana has on their kids' brains,
they would be up in arms," Evins said. 
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