Drug Addiction as a Developmental Disorder

<http://www.nytimes.com/2003/06/24/health/24DRUG.html?ex=1057032000&en~fe81a958e5bbf6&eiP62&partner=GOOGLE>

June 24, 2003

Drug Addiction as a Developmental Disorder
By JOHN O'NEIL

A new study from Yale suggests that drug addiction should be thought
of as a developmental disorder, because the changing circuitry of
teenagers' brains appears to leave them especially vulnerable to the
effects of drugs and alcohol.

Dr. R. Andrew Chambers of the Yale School of Medicine, lead author of
the article, said addictive drugs worked by stimulating parts of the
brain that are changing rapidly in adolescence.

In particular, Dr. Chambers said, the drugs tap into a neural
imbalance that may underlie teenagers' affinity for impulsive and
risky behavior. The circuitry that releases chemicals that associate
novel experiences with the motivation to repeat them develops far more
quickly in adolescence than the mechanisms that inhibit urges and
impulses.

As a result, he said, teenagers are not only more likely to experiment
with drugs than other groups, but the experience also has more
profound effects on the brain - and sometimes permanent ones.

The article, published in the June issue of The American Journal of
Psychiatry, was based on a review of 140 earlier studies. Dr. Chambers
wrote that although it had long been known that most addicts began
using drugs in adolescence, most research into the mechanisms of
addictions or treatment focused on adults.

Shifting to a model that links vulnerability to normal developmental
changes in the brain could lead to new methods of prevention or ways
of singling out teenagers at higher risk for drug use, he said.

Dr. Chambers acknowledged that social factors appeared to play a role
in drug addiction but said they did not account entirely for greater
levels of drug use among adolescents.

His analysis covered three aspects of teenage behavior and their basis
in brain functioning - attraction to novelty, less than adult levels
of judgment and an overriding interest in sex. Teenagers are drawn to
new activities and experiences, a process that Dr. Chambers referred
to as "the expansion of their motivational repertory."

"That's a good thing," he said, "because adolescents have to learn how
to be adults." But to aid the process, the motivational circuitry of
the brain - the complex of chemical reactions that make certain
experiences more desirable than others - is also rapidly expanding. It
is this circuitry, centered on the chemical dopamine, that is at the
heart of the addictive effects of a wide range of drugs as different
as cocaine and alcohol, Dr. Chambers said.

At the same time, the parts of the frontal cortex that are activated
by adults when they weigh risks and rewards lag developmentally.

"You have a situation where the motivational brain areas are
particularly active," Dr. Chambers said, "and the part of the brain
that is supposed to inhibit impulses is not working well, because it
is sort of under construction."

The other part of the equation lies in a number of brain regions that
are reshaped in adolescence as they respond to soaring levels of sex
hormones. Dr. Chambers said that rapid change seemed to leave young
people unusually attuned to all sorts of new social and sexual
stimulation, which in turn appeared to make the brain more open to the
addictive effect of drugs.