STUDY: MARIJUANA EASES TRAUMATIC MEMORIES

PHILADELPHIA - Scientists have known for years that the brain makes
substances almost identical to the active ingredient in marijuana, but the
function of these "cannabinoids" remained mysterious. Researchers now say
they help to extinguish traumatic memories.

"In certain situations, being able to forget is very important for
emotional survival," said George Kunos, a neurobiologist at the National
Institutes of Health.

The research, published today in the journal Nature, is not an endorsement
for pot smoking, scientists said. Instead, the findings may help scientists
develop new drugs to treat anxiety, post- traumatic-stress disorder and
phobias.

"This paper is not saying you should go ahead and smoke marijuana," said
Pankaj Sah, a neuroscientist at the Australian National University in
Canberra who wrote an accompanying editorial in the journal. "It's saying
that it's worth thinking about these specific actions of these compounds."

In the 1980s, scientists were surprised to find the brain has special
receptors for the psychoactive elements in cannabis, Kunos said. An Israeli
scientist named Rafael Mechoulam then found that the brain made its own
versions of these cannabinoids.

To figure out why, authors of this latest study, from the Max Planck
Institute of Psychiatry in Munich, Germany, decided to examine mice that
had been engineered genetically so that they lacked cannabinoid receptors.

Neuroscientist Beat Lutz said he and his colleagues conditioned the mice to
associate a mild shock with the sound of a bell. Normal mice eventually
lost the association between the bell and the shock. "They figure out that
the tone is not dangerous anymore and say, 'I don't have to freeze,' " Lutz
said.

But the mice lacking the cannabinoid system never readjust, always freezing
in terror at the sound.

Researchers also found that normal mice produce the natural cannabinoids
when they are extinguishing their traumatic association with the bell.

It's not clear whether the cannabinoid system helps the mice to forget the
traumatic association of the bell and the shock, or just gives them enough
mental flexibility to adjust to a new situation, Lutz said. It's possible
that the cannabinoids are important for the ability to relearn and readjust
in a number of situations.

Kunos, from the National Institutes of Health, said that the cannabinoids
probably play other roles. Using similar methods to Lutz, he found that
they help regulate appetite.

Sah, of the Australian National University, said the latest findings may
explain why some people with psychiatric problems try to find relief with
marijuana. Although experts often have labeled marijuana use as a
contributor to these people's mental illness, he suggested that people with
certain psychiatric problems perhaps are self- medicating in an attempt to
help their brains extinguish some painful or traumatic memory or thought.

Lester Grinspoon, a pro-marijuana psychiatrist at Harvard University and
author of the 1971 book "Marijuana Reconsidered," said he would like to see
cannabis made into pills that could be prescribed, but said the drug is not
patentable and therefore would be unattractive for drug companies to
manufacture and market.

Lutz suggested that, instead of supplying extra cannabinoids, a drug might
enhance the effects of natural ones.

He also suggested such a drug might need to be taken in conjunction with
psychotherapy, during which patients would work on getting rid of fearful
associations.

"Just smoking marijuana all day won't help," he said.