Pubdate: Mon, 17 Jun 2019
Source: New York Times (NY)
Copyright: 2019 The New York Times Company
Authors: Kenneth L. Davis and Mary Jeanne Kreek


Recent efforts to legalize marijuana in New York and New Jersey have
been stalled - but not killed - by disputes over how exactly to divvy
up the revenues from marijuana sales and by worries about drugged
driving. Those are both important issues. But another concern should
be at the center of this debate: the medical implications of
legalizing marijuana, particularly for young people.

It's tempting to think marijuana is a harmless substance that poses no
threat to teens and young adults. The medical facts, however, reveal a
different reality.

Numerous studies show that marijuana can have a deleterious impact on
cognitive development in adolescents, impairing executive function,
processing speed, memory, attention span and concentration. The damage
is measurable with an I.Q. test. Researchers who tracked subjects from
childhood through age 38 found a consequential I.Q. decline over the
25-year period among adolescents who consistently used marijuana every
week. In addition, studies have shown that substantial adolescent
exposure to marijuana may be a predictor of opioid use disorders.

The reason the adolescent brain is so vulnerable to the effect of
drugs is that the brain - especially the prefrontal cortex, which
controls decision making, judgment and impulsivity - is still
developing in adolescents and young adults until age 25.

In addition, researchers now have a good understanding of how
marijuana in particular affects the brain. The chemical in marijuana
responsible for producing mood elevation and relaxation, THC,
interferes with the exchange of information between neurons. Regular
exposure to THC in adolescents can permanently change neuropathways
that are related to cognition, including learning, attention and
emotional responses. In some adolescents, it can also lead to
long-term dependence.

This is why the American Academy of Pediatrics has warned against both
medical and recreational use of marijuana by adolescents. (In adults,
some medicinal forms of THC are approved for specific indications,
such as nausea caused by cancer chemotherapy. The major
nonpsychoactive component of marijuana, CBD, has been medically
approved for specific types of epilepsy and other uses.)

The risk that marijuana use poses to adolescents today is far greater
than it was 20 or 30 years ago, because the marijuana grown now is
much more potent. In the early 1990s, the average THC content of
confiscated marijuana was roughly 3.7 percent. By contrast, a recent
analysis of marijuana for sale in Colorado's authorized dispensaries
showed an average THC content of 18.7 percent.

The proposals for legalizing marijuana under consideration in New York
and New Jersey allow for use starting at age 21. While society may
consider a 21-year-old to be an adult, the brain is still developing
at that age. States that legalize marijuana should set a minimum age
of no younger than 25. They should also impose stricter limits on THC
levels and strictly monitor them. Educational campaigns are also
necessary to help the public understand that marijuana is not harmless.

Simply because society has become more accepting of marijuana use
doesn't make it safe for high school and college students. Cigarettes
and alcohol, both legal, have caused great harm in society as well as
to people's health, and have ruined many lives. Marijuana may do the
same. We must tightly regulate the emerging cannabis industry to
protect the developing brain.

Kenneth L. Davis is the president and chief executive of the Mount
Sinai Health System. Mary Jeanne Kreek is the head of the Laboratory
of the Biology of Addictive Diseases at Rockefeller University.
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