Studies review marijuana link to hard drugs

'Biochemical pathway' topic of exploration

TIMESPOST NEWS SERVICE

WASHINGTON In a finding sure to add fuel to the debate over the medical
and recreational use of marijuana, two studies released today strongly
suggest that pot is a "gateway" drug whose use leads some people to abused
socalled hard drugs, such as cocaine and heroin.

One study in the journal Science, produced by a team at the Scripps
Research Institute in San Diego, demonstrates that the stress and anxiety
associated with withdrawal from longterm use of marijuana produces the
same biochemical changes associated with withdrawal from harder drugs. This
is the "negative reinforcement" that causes a person to take more drugs to
alleviate the stress.

A second study from Italy emphasizes the opposite side of the coin,
positive reinforcement. It demonstrates for the first time that marijuana
activates the same pleasure centers in the brain that are targeted by
heroin, cocaine, and alcohol, again providing a reason to seek out the drug.

"We now have ... a smoking gun a biological mechanism by which this
gateway phenomenon could be occurring," said Dr. Herbert Kleber, medical
director of the National Center on Addiction and Substance Abuse at
Columbia University.

The new studies are unlikely to provide the final word in the ongoing
dispute about the risks associated with marijuana use, both sides said. But
they will provide powerful arguments for those opposed to marijuana use and
may change the terms of the debate somewhat, said Scripps neuroscientist
George F. Koob.

"This blurs the distinction between what is considered a hard and a soft
drug," Dr. Koob said, "because they all do the same thing."

The backdrop to the argument is government statistics unquestioned by
both sides that show that an individual who uses marijuana is 17 times
more likely to use cocaine than one who never smoked pot.

But the interpretation of these statistics varies dramatically. Marijuana
proponents argue there may be a progression because a person who smokes pot
has to buy it from an illegal dealer and is thus more likely to be around
dealers of other illicit drugs.

Alternatively, proponents argue, use of marijuana might be a marker for
deviant behavior in general, behavior that is likely to include using other
drugs.

Opponents, however, argue that marijuana use triggers a biochemical pathway
that, in effect, primes the brain for the use of other drugs. The two new
papers support this possibility.

"I'm not saying [marijuana] is as dangerous a heroin," neuroscientist
Gaetano Di Chiara told Science, "but I'm hoping people will approach
marijuana far more cautiously than they have before."