Findings back pot as 'gateway'
Research compares drug to cocaine, heroin in brain

06/27/97

By Sue Goetinck / The Dallas Morning News

Marijuana can cause chemical changes in the brain that may make chronic
users succumb more readily to heroin or cocaine addiction, researchers
have discovered.

The findings, which appear in Friday's issue of the journal Science, are
among the first laboratory evidence that could explain why smoking pot
can lead to abuse of the harder substances. That phenomenon has led
experts to call marijuana as well as alcohol and nicotine a
"gateway" drug.

The new results don't definitively explain the gateway phenomenon, said
Dr. Alan Leshner, director of the National Institute on Drug Abuse in
Rockville, Md. But the similarity of marijuana to heroin and cocaine
should be cause for concern.

"More and more we've been learning that there is a common essence to
addiction," he said. "Hopefully ... [the studies] will have made clearer
that marijuana is similar to other addictive drugs."

And, he said, the similarities between the drugs raises hopes that
future treatments for addiction or withdrawal for one drug would also
apply to people addicted to others.

Two reports in the journal described the effect of marijuana on brain
chemistry in laboratory rats. One study looked at withdrawal, the other
at the pleasurable effects of marijuana.

Friedbert Weiss and George Koob, neuropharmacologists at the Scripps
Research Institute in La Jolla, Calif., along with researchers from
Madrid, studied what happens to the brain's chemical balance after
withdrawal from a compound similar to tetrahydrocannabinol, commonly
called THC, the substance that gives marijuana users their high.

Upon withdrawal from the drug, the animals became anxious they rubbed
their faces and treaded with their paws. And, the researchers found, a
stressrelated hormone called corticotropinreleasing factor, or CRF,
was released in the rats' brains. Scientists know the same thing happens
in lab animals during withdrawal from addiction to cocaine, alcohol and
opiates such as heroin.

The second study, performed by researchers at the University of Cagliari
in Italy, showed that one of the chemical systems in the brain
responsible for giving heroin users their high is also activated by THC.

More studies will be needed to prove that marijuana use really can prime
the brain for addiction to heroin or cocaine, Dr. Koob said. If it's
true, it could be because of chemical changes induced during a high or
during withdrawal, he said. Researchers believe that addiction involves
craving to repeat a high or to relieve withdrawal symptoms, or a
combination of the two.

For years, legislators have debated whether marijuana should be
legalized for medical uses. Measures approved by voters in California
and Arizona last year that would legalize medicinal marijuana use are
being challenged in the courts.

Dr. Koob said his study doesn't address the effect of marijuana used for
medical purposes. He noted that morphine which, like heroin, is an
opiate has relieved "extraordinary amounts of distress" even though it
has the potential for abuse.

The results of the studies don't mean that anyone who uses marijuana
will become addicted to cocaine or heroin, Dr. Koob said. But for
example, he said, almost all heroin addicts have smoked pot first. And
according to the National Center on Addiction and Substance Abuse at
Columbia University in New York, children who have used marijuana are 85
times more likely to use cocaine than kids who have never smoked
marijuana.

Dr. Koob also said he hoped the new results would help people realize
that addiction to any drug is a physical, not a psychological, matter.

"Linking it up to the biology really puts a twist to it that makes
people pay attention," he said. "And to recognize that we're talking
about disorders of the body and not spirits running around somewhere."