DRUG ADDICTION AS A DEVELOPMENTAL DISORDER

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.