Brain studies find heavy pot use may lead to hard drugs

New York Times News Service

People who regularly smoke large amounts of marijuana may experience
changes in their brain chemistry that are identical to changes seen in the
brains of people who abuse heroin, cocaine, amphetamines, nicotine and
alcohol, scientists have found.

The findings, based on studies of rats, are being published today in the
journal Science. They provide strong support for the emerging idea that all
addictive drugs corrupt the same brain circuits, although to varying
degrees, and suggest that chronic marijuana use may literally prime the
brain for other drugs of abuse, a notion known as "the gateway effect."

Although the studies were conducted on rats, researchers are confident the
findings will apply directly to humans; virtually all of the biological
mechanisms known to cause drug addiction were discovered in animal models
before being established in humans.

People who oppose the legalization of marijuana will be happy about these
findings, while those who feel that marijuana is a benign drug will
probably be upset, said Dr. Alan Leshner, director of the National
Institute on Drug Abuse in Rockville, Md., which financed the research.

But beyond political arguments about the safety of marijuana, he said, "the
findings are tremendously exciting for they point to a deeper understanding
of how addiction arises, to a common essence of addiction" and may
ultimately lead to new ways of treating drug abuse.

According to this new hypothesis, addictive drugs like nicotine, heroin and
cocaine all work through common pathways in the brain. One pathway is
responsible for feelings of reward, and a second pathway underlies feelings
of anxiety brought on by stress. In street drug parlance, one system
produces the "high" while the other produces withdrawal.

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